Hematocrit – StatPearls – NCBI Bookshelf

Introduction

The term “hematocrit (HCT)” originated from English “hemato-“ and Greek “krites.” HCT measures the volume of packed red blood cells (RBC) relative to whole blood. Hence, it is also known and reported as a packed cell volume (PCV). It is a simple test to identify conditions like anemia or polycythemia and also to monitor response to the treatment. A glass tube and a centrifuge machine are sufficient to measure HCT. After centrifugation, the component of blood separates into three distinct parts. From below upwards, the layers are – a layer of red blood cells (RBC), a layer of white blood cells(WBC) and platelets, and a layer of plasma at the top. This method of determining HCT by Wintrobe hematocrit tube is known as the “macro-hematocrit” method.[1] 

A Wintrobe tube is a narrow glass tube measuring 110-mm-long, with graduation from 0 to 100 mm in both ascending and descending order.   This method has been succeeded by the “micro-hematocrit” method which uses a small capillary tube instead of a Wintrobe hematocrit tube. It requires less quantity of blood as well as less time requirement for the testing procedure. It is beneficial for patients from whom blood collection is difficult (e.g., pediatric patients/hypovolemia). However, the principle of the test remains the same as the “macro-hematocrit” method. HCT calculation is by dividing the lengths of the packed RBC layer by the length of total cells and plasma. As it is a ratio, it doesn’t have any unit. Multiplying the ratio by 100 gives the accurate value, which is the accepted reporting style for HCT. A normal adult male shows an HCT of 40% to 54% and a female shows 36% to 48%.[2] Though these two methods are still in use in some settings of primary care and medical teachings, they are widely replaced in the majority of settings by an automated analyzer, where HCT reports get generated along with the complete blood count.  

Specimen Requirements and Procedure

For the macro-hematocrit method, venous blood is taken as a random sample (i.e., no special precautions needed) maintaining proper aseptic precautions. The blood is either collected in a commercially available vacutainer containing ethylenediaminetetraacetic acid (EDTA) or in a vial/test tube with EDTA where vacutainer is not available[3]. For the microhematocrit method, the blood requirement is less, and single finger-prick blood is sufficient. Heparin filled capillary tube may is used to collect blood. However, if there is available blood with anticoagulant for other hematologic tests, a capillary tube without heparin can be used. For measurement of HCT in automated hematologic cell counter, blood with anticoagulant used for CBC is necessary.

Testing Procedures

The macro-hematocrit method uses a Wintrobe hematocrit tube, a centrifuge machine, and a Pasteur pipette. Blood is filled in Wintrobe hematocrit tube up to 100 mm mark by the help of Pasteur pipette. Care is taken not to leave any bubble in the blood column. For this, the tube is filled slowly with the tip of the pipette being always below the highest position of the blood column. Then, the tube gets placed in the centrifuge machine. When testing a single specimen, another blood-filled Wintrobe hematocrit tube is kept on the opposite holder to counterbalance. The spin setting is 3000 rpm for 30 min. After completion of the centrifugation, the tube is taken out, and RBC column height is reported as HCT. During the reporting, special precaution is necessary to omit the buffy coat, which is a combination of WBC and platelets. This layer should not be included in the HCT, as it may lead to false positive results.

For the microhematocrit method, after filling the blood in a capillary tube, the two ends of the tube (commonly 75 mm long, 1 mm diameter) are sealed with clay sealant or heat. Then, it is centrifuged at a rate of 11000 to 12000 rpm for 4 to 5 min. Reading is with the help of the scale on a tube holder or microhematocrit card reader.

The automated analyzer measures the average RBC size and number by the “Coulter principle”[4]. In this method, the size and number of the RBCs is measurable by detecting impedance while the blood passes through a passage between two electrodes.

Interfering Factors

There are several physiological and pathological conditions where the HCT may deviate from its normal range. New-born babies show a high HCT, and it gradually decreases during the neonatal period[5]. Adult male shows higher HCT than an adult female.[6] Pregnant women show lower HCT due to hemodilution. In high altitude, the number of RBC becomes high due to persistent hypoxia; hence, the inhabitant of high altitude shows higher HCT. Methodological variation may provide a minor deviation of HCT tested for the same sample. In the macro-hematocrit method, there is an increased amount of trapped plasma (approximately 2%) in the packed RBC, which may give a higher HCT. This factor becomes minimized in the microhematocrit method, where the amount of trapped plasma is less as the diameter of the capillary tube is less than that of the Wintrobe hematocrit tube. Blood collected from different sources may also show variation. Venous blood shows higher HCT than arterial blood. However, there is no difference in HCT between venous blood and finger prick blood.[7]

Results, Reporting, Critical Findings

Wintrobe hematocrit tube has graduation 0 to 100 from below upwards. Hence, the highest level of packed RBC is the HCT in percentage. For the microhematocrit method, the reading is from the HCT card or scale. However, for these two methods, even without any graduation or scale, the HCT value can be calculated with a simple scale as we compare the length of the RBC column with the total length of the fluid column. The final report is a percentage. HCT, along with RBC count and hemoglobin (Hb) concentration, is used to report other blood indices manually as follows:

The mean corpuscular volume (MCV) calculation uses HCT and RBC count.

Mean corpuscular hemoglobin concentration (MCHC) is calculated with Hb concentration and HCT.

Clinical Significance

In primary health care settings, especially in resource-limited settings, macro-hematocrit and micro-hematocrit methods are two low-cost and simple tests for determining RBC in blood. Clinically, HCT is used to identify anemia and polycythemia along with other parameters (e.g., RBC count, Hb concentration). In anemia, where there are fewer RBCs in the circulating blood relative to the total volume of the blood, the HCT decreases.[8] In polycythemia, there is a higher number of RBCs in the blood; HCT increases. Smokers and chronic obstructive pulmonary disease (COPD) patients also have high HCT due to chronic hypoxia. The increase in HCT increases the viscosity of the blood, so does the peripheral resistance. Hence, patients with higher HCT may have higher blood pressure.

Quality control and Lab Safety

Handling of blood should take place with the maintenance of proper aseptic precautions. The collected blood should be tested as soon as possible after collection. Prolonged storage at the room temperature would result in a change in the shape of the RBCs due to metabolism. After about 6 hours, the chances of hemolysis increase, which would give an erroneous result. In the macro-hematocrit method, the filing of the Wintrobe hematocrit tube requires proper care. In the microhematocrit method, the sealing of the capillary tube should be secure to prevent any leakage. The centrifuge machine should not be opened during the test to avoid erroneous results. The chances of error in the result will increase if the centrifugation is interrupted. Immediately after completion of the rotation, the operator should not open the lid should until after the complete stoppage of the rotation. For reuse of the Wintrobe hematocrit tube, proper cleaning is necessary as any foreign particle inside the tube would be counted either in the RBC column or plasma column.

Enhancing Healthcare Team Outcomes

After the introduction of the automated hematology cell counters, the usage of macro-hematocrit and microhematocrit method is less used nowadays. However, in many resource-poor settings, it is still used for the diagnosis of anemia and polycythemia and monitoring response to treatment. In a rural healthcare facility, it is a more accurate method for identifying anemia than the total RBC count, as chances of error in manual RBC count is very high. The micro-hematocrit method is more acceptable as it requires less amount of blood, and the testing time is very less in comparison to the macro-hematocrit method. Due to the requirement of less amount of blood and less time for the test, it may be useful in a mass survey.

Figure

Wintrobe hematocrit tube containing components of blood after centrifugation. Contributed by Shaikat Mondal, MD

a review of different analytical methods

INTRODUCTION

This article describes the advantages and
disadvantages of the different methods of measuring hematocrit
by discussing the following:

• The components of whole blood
• Indications for measuring hematocrit
• Measuring technologies 
  
  1.  Microhematocrit
  
  2. Complete blood cell count
  
  3. Conductivity on blood gas analyzers
  
  4. Calculation of hematocrit
• Comparison of the different technologies

This article will be followed by another article describing
the different methods of determining hemoglobin.

THE COMPONENTS OF WHOLE BLOOD

Whole blood is comprised of erythrocytes (the red blood cells
or RBCs involved in oxygen transport), platelets and leukocytes
(the white blood cells or WBCs involved in the body’s immune
defense). The cells are suspended in the aqueous medium of
plasma. 

In blood from healthy individuals, erythrocytes
constitute the vast majority of cells; the erythrocytes contain
hemoglobin (Hb), which gives blood its red color and which has
oxygen-binding abilities. Plasma mainly consists of water
(approx. 93 %) but also of salts, various proteins and lipids
as well as other constituents, e.g. glucose.

FIG. 1. A centrifugated whole-blood
sample

The definition of hematocrit (hemato from the Greek haima =
blood; crit from the Greek krinein = to separate) is the ratio
of the volume of packed red blood cells to the total blood
volume and is therefore also known as the packed cell volume,
or PCV. 

The hematocrit is reported as a percentage or a ratio.
In healthy adult individuals the red blood cells constitute
approx. 40-48 %, whereas newborns may have hematocrits of up to
60 % [1]. 

The layer between the RBCs and plasma, the buffy coat
layer, constitutes approx. 1 %. It consists of WBCs and
platelets and should therefore not be calculated as part of the
packed cell volume.

The relationship between hematocrit and
hemoglobin

The following is a summary of the quantities/abbreviations that
are relevant when discussing hematocrit:

• Hct: Hematocrit (% or volume fraction)
• ctHb: Concentration of total hemoglobin (g/dL,
  g/L or mmol/L)
• RBC: Red blood cell (erythrocyte) (×
  10¹²/L)
• MCV: Mean cell volume (fL)
• MCHC: Mean corpuscular hemoglobin concentration
  (%, g/L or mmol/L)

In normal conditions there is a linear relationship between
hematocrit and the concentration of hemoglobin (ctHb).
An empirical study [2] has shown that the relationship can be
expressed as follows:

Hematocrit can also be estimated from measurements of the
mean cell volume (MCV) or the mean corpuscular hemoglobin
concentration (MCHC):

INDICATIONS FOR MEASURING HEMATOCRIT

Hematocrit measurements may be requested when it is suspected
that a patient is anemic or suffering from dehydration,
bleeding or other medical and surgical conditions.

Low hematocrit

A low hematocrit reflects a low number of
circulating red blood cells and is an indicator of a decrease
in the oxygen-carrying capacity or of overhydration. Examples
of conditions causing a low hematocrit (anemia) include
[3]:

• Internal or external hemorrhage – bleeding
• Complication of chronic renal failure – kidney
  disease
• Pernicious anemia – vitamin-B12 deficiency
• Hemolysis – associated with transfusion reactions

A low hematocrit may be found in autoimmune diseases and
bone-marrow failures.

High hematocrit

A high hematocrit may reflect an absolute increase in the
number of erythrocytes, or a decrease in plasma volume, in
conditions such as [3]:

• Severe dehydration – e.g. in case of burns, diarrhea or
  excessive use of diuretics
• Erythrocytosis – excessive red blood cell
  production
• Polycythemia vera – abnormal increase of blood
  cells
• Hemachromatosis – an inherited iron metabolism
  disorder

High hematocrit is also used as an indicator of the
excessive intake of exogenous erythropoitin (EPO), which
stimulates the production of red blood cells. Athletes can
artificially improve their performance by enhancing the
oxygen-carrying capacity with EPO.

In newborns and especially premature babies, high hematocrit
values are common. The hematocrit of infants reaches the level
of adult hematocrit by approx. three months of age [1].

The conditions leading to low hematocrit values, e.g.
hemorrhage, often require continuous measurements of the
hematocrit and fast decisions concerning transfusions. If the
hematocrit is measured immediately after an acute hemorrhage,
the value will be normal until the decreased blood volume is
corrected by fluid shifts into the blood vessels.

MEASURING TECHNOLOGIES

This section gives a technical description of the most commonly
used techniques for measuring hematocrit:

1. The determination of hematocrit by means of
   centrifugation
2. The calculation of hematocrit from the complete blood
   cell count (CBC)
3. The determination of hematocrit by conductivity
4. The calculation of hematocrit from ctHb

1. Microhematocrit

The reference method recommended by NCCLS of
determining hematocrit or packed cell volume (PCV) is
centrifugation.

Method [4]:

Hematocrit (PCV) is the measure of the ratio of the
volume occupied by the red blood cells to the volume of whole
blood. The blood sample is drawn into a capillary and
centrifugated, and then the ratio can be measured and expressed
as a decimal or percentage fraction.

Materials:

• Whole blood from a freely flowing skin puncture or
  anticoagulated (EDTA or heparin) venous or arterial
  blood
• Glass capillary tubes with a narrow diameter
• Sealing compound (if the capillaries are not
  self-sealing)
• A microhematocrit centrifuge with a maximum relative
  centrifugal force of 10-15,000 × g, which should be
  reached within 30 seconds [4]
• Graphic reading device

Procedure:

• Capillary tubes are filled by capillary forces. A
  minimum of two capillaries is required to ensure balance in
  the centrifuge. It is important that the tubes are sealed
  thoroughly.
• After five minutes of centrifugation the hematocrit can
  be measured while the tubes are still kept in a horizontal
  position. A distinct column of packed erythrocytes is
  visible in one end of the capillary tube (Fig. 2). The
  packed erythrocytes are followed by first a small turbid
  layer – the buffy coat layer – and then a clear column of
  plasma (Fig. 2). Hematocrit is estimated by calculating the
  ratio of the column of packed erythrocytes to the total
  length of the sample in the capillary tube, measured with a
  graphic reading device.
• The measurement should be performed within 10 minutes
  to avoid merging of the layers.

FIG. 2. Reading the hematocrit

Limitations:

• Studies have shown that spun hematocrit gives values
  approx. 1.5-3.0 % too high due to plasma trapped in the RBC
  layer. If abnormal types of RBCs are present, this bias can
  be even greater, as more plasma is trapped [5]. See also
  Table I.

2. Complete blood cell count (CBC)

In hematology laboratories, automatic cell count
analyzers measuring multiple parameters are the most commonly
used.

Method:

The hematocrit is determined indirectly from the
average size and number of RBCs. The reference method is the
Coulter impedance principle [6] and is described below.

Materials:

• Sample tubes normally containing 3-5 mL EDTA
  anticoagulated blood

Procedure:

• The whole-blood sample is diluted automatically with an
  isotonic solution prior to analysis.
• The diluted blood is forced through an orifice which
  has two electrodes placed on opposite sides (Fig. 3).
• By applying a constant current between the two
  electrodes, the impedance is constant until a blood cell
  passes through the orifice
• Due to the non-conductive properties of the red blood
  cell membrane, the electrical resistance increases each
  time an erythrocyte passes through the orifice.
• The change in potential between the electrodes
  correlates to the volume of the passing erythrocyte.
  Furthermore, erythrocytes that have passed through the
  orifice are counted. From the mean cell volume, the
  erythrocyte count and the dilution factor, the hematocrit
  is derived.

FIG. 3. The Coulter principle

Limitations:

• When a high reticulocyte or WBC count is present,
  hematocrit determinations using hematology analyzers can
  result in the calculation of falsely elevated values,
  because the higher cell volumes of these cells will
  interfere with the red blood cell count and the calculation
  of the hematocrit [7]. See also Table I.

3. Conductivity on blood gas analyzers

In POCT, blood gas analyzers measuring multiple
STAT parameters are often used. Some blood gas analyzers
determine hematocrit by a conductivity measurement which is
corrected for the concentrations of conducting ions in the
sample.

Materials:

• Syringes or capillaries containing heparinized arterial
  or venous blood

Method:

• The conductivity is the ability of a solution to
  transmit (conduct) electricity. The electrical current will
  increase in proportion to the number of ions (or charged
  particles) found in a solution, their electrical charge and
  mobility, i.e. how easily the ions can move in the
  solution. The mobility of an ion in a solution will also
  depend on how many cells (and size and shape) are
  suspended in the solution.
• Both erythrocytes and plasma have characteristic
  electrophysical properties. The membrane of the
  erythrocytes is electrically insulating, mainly due to its
  content of lipids, so that it appears essentially
  non-conducting.
• Plasma is fairly conductive due to its content of
  electrolytes and charged proteins; the major contributor to
  plasma conductivity is Na+, the concentration in human
  blood plasma being approx. 140 mmol/L.
• Due to this, there is an inverse relationship between
  the electrical conductance and the hematocrit in blood when
  the concentration of the charged particles is taken into
  account.

Three factors besides the number of RBCs are critical for
the determination of the hematocrit value when using a method
based on measurement of electrical conductivity:

1. Electrolytes
2. Temperature
3. Proteins

Most blood gas analyzers allow for these variables as
follows:

• Concentration of electrolytes: This is determined by
  one or more ion measurements. As sodium is the primary
  electrolyte in plasma, this is the most important ion to
  measure and use in the calculation of hematocrit.
• A change in the temperature has a significant impact on
  the conductivity because blood has a high temperature
  coefficient. The measuring chamber in blood gas analyzers
  is thermostatted and the blood sample preheated prior to
  measurement; thus there is no contribution from changing
  temperature.
• The protein concentration in plasma is assumed constant
  in healthy people, so a constant compensation for this is
  incorporated in the calculation of hematocrit on blood gas
  analyzers.

Limitations:

• In patients with abnormal plasma osmolality, e.g.
  patients being treated with plasma expanders, blood
  diluents or massive infusion therapy, the protein
  concentration is no longer constant and the hematocrit
  determination gives falsely low values [8, 9]. Some blood
  gas analyzers offer correction for this bias [10,11,12].
  See also Table I.

4. Calculation of hematocrit from hemoglobin

As there is a linear relationship between
hemoglobin (ctHb) and hematocrit as described earlier,
it is possible to calculate the hematocrit on analyzers that
measure hemoglobin. When making this conversion, two factors
should be taken into consideration:

• The analytical quality of the ctHb
  measurement
• The precision of the equation that converts the two
  parameters

The measurement of ctHb from most good-quality
analyzers is usually reliable; however, the equations used to
calculate the hematocrit vary from analyzer to analyzer. Some
analyzers use an empirically found equation [2,13] whereas
others use an approximate conversion factor of 3 [14,15].

Example:

TABLE I: Effect of different conversion factors on
Hct %.

* Conversion factor: g/dL × 0.62058 = mmol/L

Limitations:

• It is generally assumed that the conversion from
  hemoglobin to hematocrit is straightforward since most
  methods measuring ctHb are considered to be fairly
  accurate; however, different analyzers use different
  conversion factors, which may compromise the reliability of
  the hematocrit result. Hematocrit and hemoglobin are often
  used interchangeably; however, different studies have shown
  that the two parameters are not comparable, but that they
  have their separate applications [15,17,18,19]. 

Comparing measuring technologies

All measuring technologies for determining hematocrit have
advantages and disadvantages. The following table provides an
easy overview of the described methods. The
advantages/disadvantages listed have all been found by
reviewing the literature, i.e. no prioritizing according to
importance has been done.

Table as word document.

TABLE IIa. Advantages of different methods of
measuring hematocrit.

TABLE IIb. Disadvantages of different methods of
measuring hematocrit.

Discussion

When hematocrit is used to assess anemia and the
oxygen-carrying capacity, the advantages and disadvantages of
each method must be carefully considered. In addition, the
specific clinical and analytical needs for any patient
population must be determined.

Hematocrit is traditionally a routine hematology laboratory
parameter; however, measuring hematocrit as a STAT parameter in
a POC setting is in many ways preferable, as this will save
time in critical situations and avoid specimen transport
problems. Some blood gas analyzers offer this possibility,
either by measuring hematocrit by conductivity or by
calculating hematocrit from ctHb. 

Hemoglobin is also used to assess anemia both in the
laboratory and as a STAT parameter on POCT analyzers. Different
hemoglobin measuring methods and their applications will be
discussed in another article.

Conclusion

Both POCT and traditional laboratory methods of measuring or
calculating hematocrit have limitations. Methods used outside
of the laboratory must be intuitive for users without
time-consuming sample handling. 

Methods suitable for an adult
environment may not be suitable for a neonatal environment due
to sample volume limitations. Some methods are not suitable in
certain applications due to e.g. problems associated with
volume expansion fluids or abnormally sized or shaped red blood
cells. 

These limitations can have important clinical
implications and must be carefully considered as described in
this article.

Hematocrit – Complete Blood Count

Hematocrit – Complete Blood Count

 Hematocrit

The hematocrit,
also known as the “Hct“, “crit”
or PCV (packed cell volume) determines the percentage of red
blood cells in the plasma. The term hematocrit means “to separate blood.”
When the patient’s blood sample is spun in a centrifuge, the white blood cells
and platelets rise to the top in what is known as the “buffy coat.”
The heavier red blood cells sink to the bottom, where they can be calculated
as a percentage of the total blood sample.

Normal hematocrit values
are:

• Newborn: up to
  60%
• Adults: (males):
  40- 54%
• (Females): 36
  – 46%
• Pregnancy: decreased
  hematocrit, especially in the last trimester as
  plasma volume increases
• Children: varies
  with age

If the RBC
and the hemoglobin are both normal, it is possible to estimate
the hematocrit as being approximately three times the hemoglobin. For example,
a person whose hematocrit is 30% would have a hemoglobin of approximately 10
gm.

Instant
Feedback:

Pregnant
women normally have a drop in hematocrit in the last trimester of pregnancy.

Because the hematocrit
is a percentage of red blood cells, as compared to the total volume of blood,
any increase or decrease in plasma volume affects the hematocrit.
A patient with a severe burn loses huge amounts of plasma from damaged capillaries.
As a result, the vascular space loses fluid in relation to cellular elements
and the patient’s hematocrit will be significantly increased.
A decreased hematocrit occurs due to overhydration, which lowers
the percentage of red blood cells in relation to the liquid plasma portion of
blood.

A hematocrit
is frequently done to assess the extent of significant blood loss. A hematocrit
that is done immediately after a hemorrhage usually does not show the extent
of RBC loss because at the time of the hemorrhage, plasma and red blood cells
are lost in equal proportions. However, within several hours after hemorrhage,
plasma volume increases due to a shift of interstitial fluid into the vascular
space. Red blood cells, however, cannot be replaced quickly, as the bone marrow
takes approximately ten days to produce mature red blood cells. As a result,
a hematocrit done several hours after a bleeding episode will
show a more accurate picture – the hematocrit will be decreased
because the plasma volume has compensated for fluid loss while the red blood
cells that have been lost cannot be replaced for days. It is important for the
nurse to remember that a hematocrit value must always be interpreted
in relation to the patient’s hydration status and to the time the sample was
drawn. When packed red blood cells are given to correct an anemia, the hematocrit
should rise approximately 3% for each unit transfused.

How a patient responds to
a low hematocrit depends on whether the blood loss is acute
or chronic. If a person with a normal blood cell volume loses blood suddenly
through a massive hemorrhage, the person may develop signs and symptoms of circulatory
shock; the blood pressure will fall and the patient will show signs of tissue
hypoxia and shock. However, a person with chronically low hemoglobin, such as
a patient on renal dialysis, may tolerate abnormally low hemoglobin. A major
reason for anemia in patients with renal failure is lack of erythropoetin to
stimulate bone marrow production.

Instant
Feedback:

Expect
a patient’s hematocrit to drop immediately after major hemorrhage.

Hematocrit: critical
low and high values:

• A hematocrit
  of less than 15% can result in cardiac failure
• A hematocrit
  of over 60% may result in spontaneous blood clotting

© RnCeus.com

Hematocrit – an overview | ScienceDirect Topics

The basis of tolerance, prediction, and confidence intervals

Hematocrit (Hct) values (measured in percent) for healthy patients are not all the same; they range over an interval. What is this interval? Because we see an occasional very high or low value in a healthy patient, we want an interval such that with a specified probability will include most of the healthy population; we name this a tolerance interval. This is an expression of relative frequency or likelihood. What is the width of this interval? We might say that the interval should include 95% of the healthy population, which is to say that a randomly chosen healthy patient has a 0.95 probability of being within the interval. This leads to the term tolerance interval, because our tolerance in specifying the certainty around this range leads up to a 5% (1−0.95) error.

Now suppose that we have constructed a model for Hct values on the basis of patient characteristics (e.g., height, weight, sex, and age) for a sampled population. Such a model might be constructed using linear regression as presented in Chapter 16, Multiple linear and curvilinear regression and multifactor analysis of variance. Given this model, we might want to predict the Hct value for a new randomly sampled patient with a given set of characteristics. However, since our prediction is based upon estimates from sampled data, we also wish to quantify how good our prediction is. Thus we wish to construct an interval around our prediction that quantifies the uncertainty in our “guess.” This interval is termed a prediction interval. A prediction interval is a range of likely values for a new observation that has a specified set of characteristics used to aid in the prediction. The precision of a prediction interval is defined by the probability that the new observation will fall in the specified range. For example, if we produce a 95% prediction interval for the Hct value of a new patient we are treating, the actual Hct of the patient should lie within the interval with probability 0.95.

Another type of goal we might have is to characterize the range of plausible values for the true mean Hct value in a population of healthy individuals. Thus we desire a range of values that characterize the population mean Hct. This type of interval is termed a confidence interval, often denoted by CI. What do we mean by confidence? Given that the true population mean Hct in a specified population is a fixed quantity, we wish to control the probability that our interval will contain the population mean. Thus if we produce a valid 95% CI for the population mean using a sample of data, we are ensuring that if we repeatedly sampled from the population and formulated such an interval, then 95% of these intervals would in fact cover the true population mean.

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Hematocrit : Nursing2020 Critical Care

Department: Looking at Labs

doi: 10.1097/01.CCN.0000654816.47865.44

Metrics

Background

Hematocrit (HCT), also called packed cell volume (PCV), means “to separate blood” and is the packed spun volume of blood that consists of intact red blood cells (RBCs), expressed as a percentage. HCT can be measured directly following centrifugation of a blood sample or calculated using the formula:

HCT = (RBC x MCV)/10. Mean corpuscular volume (MCV) is the average volume (size) of the patient’s RBCs.

HCT is part of the complete blood cell count and indirectly measures the RBC mass. The results are expressed as the percentage by volume of packed RBCs in whole blood (PCV). It is an important measurement in the determination of anemia or polycythemia.

Normal reference values in adults

• Women: 36% to 48%
• Men: 42% to 52%.

Clinical alert

An HCT under 20% can lead to heart failure and death; an HCT over 60% is associated with spontaneous thrombosis.

Clinical implications

• Decreased HCT is an indicator of anemia, a disorder in which there is a reduction in the PCV. An HCT under 30% means that the patient is moderately to severely anemic. Decreased values also occur in the following conditions:
• – leukemias, lymphomas, Hodgkin disease, myeloproliferative disorders
• – adrenal insufficiency
• – chronic disease
• – acute and chronic blood loss
• – hemolytic transfusion reactions.

• The HCT may not be reliable immediately after even a moderate loss of blood or immediately after transfusion.
• The HCT may be normal immediately after acute hemorrhage. During the recovery phase, both the HCT and the RBC count drop markedly.
• Usually, the HCT parallels the RBC count when the cells are of normal size. As the number of normal-sized erythrocytes increases, so does the HCT.
• – However, for the patient with microcytic or macrocytic anemia, this relationship does not hold true.
• – If a patient has iron-deficiency anemia with small RBCs, the HCT decreases because the microcytic cells pack to a smaller volume. The RBC count, however, may be normal or higher than normal.

• Increased HCT occurs in:
• – erythrocytosis
• – polycythemia vera
• – hemoconcentration from hypovolemia.

Interfering factors

• People living at high altitudes have a high HCT.
• Normally, the HCT slightly decreases in the physiologic hemodilution of pregnancy.
• The normal values for HCT vary with age and gender. The normal value for infants is higher because the newborn has many macrocytic red cells. The HCT in women is usually slightly lower than in men.
• There is also a tendency toward a lower HCT in men and women over age 60, corresponding to lower RBC count values in this age group.
• Severe dehydration from any cause falsely raises the HCT.

Source: Fischbach FT, Fischbach MA. A Manual of Laboratory and Diagnostic Tests. 10th ed. Philadelphia, PA: Wolters Kluwer; 2018.

Wolters Kluwer Health, Inc. All rights reserved.View full article text

Difference between Spun Hct and Automated Hct in Infants of Diabetic Mothers (IDM), Macrosomic Infants (LGA) and Normal-Sized Infants (C)

Hct determinations in neonates by an automated hematology analyzer (auto Hct) have been shown to yield lower levels than those obtained by microhematocrit tube centrifugation (sHct.) Based on random clinical observations, we tested the hypotheses that the difference (Δ) between auto Hct. and sHct is higher in IDM and in LGA than in C infants, and that this Δ is correlated positively with MCV. Infants were studied within (24) hours after birth. The sHct was determined in each sample before submission to the hospital clinical lab. The Hct difference (Δ%) between the two methods was expressed as ((sHct – autoHct)/autoHct) × 100 and the mean Δ% values for each of the 3 study groups were compared by use of the student “t” test.

Within each study group, a Pearson correlation test was performed between automated MCV value and Δ% Hct. (Table)

Table 1 No caption available

In all samples, sHct was higher than autoHct. The mean Δ% Hct was not significantly different among the groups. A significant negative correlation was found between MCV and Δ% Hct in the LGA group (p<0.001), and a trend in the IDM group (0.10>p>0.05), but no correlation in group C.

Since it has been suggested that some LGA infants might be the offspring of mothers with unrecognized gestational carbohydrate intolerance, we speculate that in some of these infants, and some of the IDM group, changes in the composition, and/or deformability of the red cells might affect the electronic determination of corpuscular size. This could result in inaccurate values for MCV, and hence of derived autoHct.

Author information

Affiliations

1. Dept. of Peds., SUNY, Children’s Med. Ctr. of Bklyn, NY

   Emad Ghaly, Gloria Valencia & Nathan Rudolph

Authors

1. Emad Ghaly
2. Gloria Valencia
3. Nathan Rudolph

Additional information

(Spon by: Stanley Fisher)

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Cite this article

Ghaly, E., Valencia, G. & Rudolph, N. Difference between Spun Hct and Automated Hct in Infants of Diabetic Mothers (IDM), Macrosomic Infants (LGA) and Normal-Sized Infants (C).
Pediatr Res 45, 262 (1999). https://doi.org/10.1203/00006450-199904020-01560

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90,000 “Why is the hematocrit in the blood increased, what does this mean?” – Yandex.Qu

An indicator of the level of erythrocytes, leukocytes and platelets for the entire blood volume in the body is called hematocrit.

Usually, this indicator is depicted as a percentage, less often as a fractional number. The definition of this indicator makes it possible to see the presence of any disease and the degree of its development.

The main reason for an increase in hematocrit is an increase in the number of red blood cells (overproduction in the bone marrow) or an increase in their size, which creates additional volume.What this means, and what causal factors contribute to this, we will consider in this article.

Hematocrit rate

For the analysis, it is necessary to take a blood sample. The biological material is placed in a sterile flask, after which the vessel is closed and sent to a centrifuge. Here the blood is subjected to a separation procedure into its constituent parts. To do this, it is in a centrifuge for one and a half hours, and during this time all components are separated from each other.

Normal hematocrit values ​​depend on a person’s gender and age:

• adult male – 40-48%;

90,015 adult women – 36-46%;

90,015 newborn children – up to 60%;

90,015 children under 13 – up to 38-40%.

If the analyzes indicate that the norm for women and men is violated and is more than 0.55, then the patient has an increased hematocrit. Due to the high concentration of leukocytes, erythrocytes and platelets in the blood, the viscosity of the blood increases, and this causes the formation and growth of blood clots in the vessels.

Signs

Frequent dizziness is the first “bell” when hematocrit values ​​are above normal. A high number of red blood cells is able to bind and carry more oxygen, leading to mild but permanent poisoning – hyperoxia.

With the progression of the disease, poisoning takes on more severe forms, causing nausea, a state of mild daze, numbness of the extremities, difficulty breathing.

Causes of increased hematocrit

Why is the hematocrit in the blood of adults increased, what does this mean? The reasons for the increase in hematocrit can be both pathological and physiological, which are not associated with certain diseases.

The body always strives to maintain the balance of internal processes, therefore, in case of deviations from physiological norms, compensating mechanisms are activated. An increase in the hematocrit in the blood is one of the quantitative characteristics of the physiological “adjustment” of the body to new living conditions.

So, let’s consider the most common causes of increased hematocrit in adults:

1. As a result of dehydration, or dehydration. In this case, the amount of circulating blood in the stream decreases due to a decrease in plasma volume.This can happen with vomiting, diarrhea, overheating, heavy sweating, and insufficient fluid intake. In this case, the body is forced to take water from the bloodstream. Thus, the ratio of the volume of the erythrocyte fraction to the total volume changes, the blood becomes thicker due to a decrease in the amount of plasma.
2. Diseases that reduce the volume of plasma in the blood. They do not affect the amount of blood elements themselves, but second-degree burns, for example, form bubbles in which plasma accumulates.It is taken just from the blood, increasing the hematocrit by reducing the second number in the indicator. This group also includes acute manifestations of diseases such as peritonitis, thrombosis or diabetes.
3. Chronic hypoxia. In this state, there is not enough oxygen in the cells and tissues of the human body. The pathology is often detected in people who smoke or

   have diabetes

   … Erythrocytes contain hemoglobin, which is responsible for moving oxygen, transporting it to cells, removing carbon dioxide from the body.With hypoxia, present in a chronic form and arising for an objective reason, the body tries to eliminate the problem of oxygen deficiency by increasing the synthesis of red blood cells. The increase in hematocrit in this case occurs precisely because of the increased production of red blood cells.

4. Long-term drug use: glucocorticoids and other hormonal drugs are especially dangerous in this regard. Diuretics also have a similar effect.
5. Getting skin burns.Moreover, the larger the area of ​​the skin lesion, the higher the hematocrit is recorded in the blood test. This is easily explained by the mobilization of all blood components to fight infections and bacteria penetrating through the burn, as well as the need for an accelerated process of tissue regeneration.
6. Kidney disease. Hydronephrosis, which reduces the body’s ability to absorb water, or neoplasms, polycystic, accompanied by increased release of erythropoietin, a hormone responsible for the formation of red blood cells.

7. Anemia

   , in which a lack of vitamin B12 and iron is found in the body.

8. Blood disease, primarily leukemia.
9. Development of peritonitis in the body.
10. Polycystic disease in acute or chronic forms.
11. Rapid development of erythremia in the body.

Obviously, the analysis only for hematocrit without determining the number of erythrocytes and their morphological characteristics is unlikely to satisfy the requests of clinicians in the diagnosis of various hematological pathologies, since the test, although it carries general information, does not reveal the cause of the increase or decrease in any way.

Therefore, when this value exceeds the norm, it can indicate both physiological processes in the body and diseases. A high hematocrit indicates thick blood, which means that there is a danger of thrombosis.

What can affect the rate of hematocrit?

An increase, as well as a decrease in hematocrit, is not necessarily associated only with diseases or external influences in the form of trauma or burns. There are at least two more factors that affect the increase in hematocrit.

1. In those who smoke, the hematocrit increases through oxygen deprivation of tissues, their erythrocytes are produced at an increased level.
2. People who are forced to work or constantly be at heights are also characterized by an increase in the level of hematocrit in the blood. This applies to climbers or simply residents of highland areas. This factor is very similar to the previous one, because a person receives an insufficient amount of oxygen – its concentration decreases with increasing altitude.
3. Elevated Ht levels are characteristic of athletes using anabolic steroids to gain muscle mass.
4. In newborns, the hematocrit is always elevated.

So, it is very important to pass an analysis for hematocrit in order to identify the development of some pathologies in time.

What to do with high hematocrit?

Successful treatment and stabilization of the hematocrit level is to eliminate the root cause. In some cases, no special methods can be used, it is enough to start breathing oxygen-enriched air, quit smoking, drink enough water and normalize your lifestyle.Also, with a strong increase in hematocrit, it is necessary to consult a doctor for the appointment of drugs that thin the blood – anticoagulants.

It should be remembered that in the case of an increase in hematocrit, the viscosity of the blood also increases. This leads to certain consequences. The risk of blood clots, which subsequently block arterial blood flow, increases. This can lead to

heart attacks

, ischemic stroke, gangrene or death, depending on the location of the blood clot.

We have collected the most useful information about what it means “increased hematocrit in the blood” so that now you can have an initial idea of ​​your CBC results. Leave comments and share useful information with your loved ones.

Effects

An increase in hematocrit is directly related to an increase in blood viscosity.

Thick blood is prone to the formation of clots, which, having gathered in a certain amount, already form a blood clot.Small blood clots begin to block the flow of blood in the thin capillary vessels, thereby blocking the supply of small areas of tissue first. A person can feel such overlap in the form of numbness, for example, of fingers, toes, as well as the death of small areas of tissue.

But large blood clots can cause, in the first place, big heart problems, up to and including death.
Way out of this situation in blood thinning. This is a well-known recommendation.

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90,000 hematocrit is … What is hematocrit?

90,000 Pass a general (clinical) blood test without a leukocyte count in the KDL

laboratory

General (clinical) blood test without formula – the main laboratory test used most often when anemia is suspected – a condition manifested by a decrease in hemoglobin and red blood cells in a blood test.A blood test without a leukocyte formula includes counting all types of blood cells (erythrocytes, leukocytes, platelets) without dividing leukocytes by type; determination of hemoglobin level, hematocrit (ratio of cell mass to plasma), determination of erythrocyte indices (MCV, MCH, MCHC). A blood test without a leukocyte count is necessary in the diagnosis and control of the treatment of anemias of various origins.

In what cases is a general blood test without a formula usually prescribed?

A blood test without a leukocyte count is necessary for the diagnosis and control of the treatment of anemias of various origins.This test is often used to monitor the number of platelets, the cells involved in blood clotting.

What exactly is determined in the analysis process?

• Erythrocytes (RBC, red blood cells) – the number of erythrocytes in 1 ml of blood is determined
• Hemoglobin (Hb, HGB, hemoglobin) – determined in g per 1 ml of blood
• Hematocrit (Ht, Hematocrit) – the percentage of cells from the total blood volume, reflects the thickening or dilution of blood.
• MCV (Mean Cell volume) – average erythrocyte volume.
• MCH (Mean Cell Hemoglobin) – the average amount of hemoglobin in one erythrocyte.
• MCHC (Mean Cell Hemoglobin Concentration) – the average concentration of hemoglobin in erythrocytes.
• Distribution of erythrocytes by volume (RDW, Red cell Distribution Width) is an indicator of the uniformity of erythrocytes.
• Platelets (PLT, Platelets) – non-nuclear blood cells (platelets).
• Leukocytes (WBC, White Blood Cell) – the total number of leukocytes in 1 ml of blood is determined without dividing them by type (without leukocyte formula).

What do the test results mean?

Decreased red blood cell count, hemoglobin count and decreased hematocrit are usually signs of anemia. By the volume of red blood cells, the doctor differentiates microcytic anemias (with a reduced volume of red blood cells) from macrocytic anemias (with an increased volume of red blood cells).

An increase in the number of leukocytes may be a sign of an ongoing infection and requires a blood test with a leukocyte count.

In addition to true thrombocytopenia (reduced platelet count), the occurrence of such a rare phenomenon as EDTA-dependent thrombocytopenia is possible. Currently, to perform a general blood test, blood is drawn into tubes with an anticoagulant – EDTA. In rare cases, the interaction of the patient’s blood with EDTA leads to aggregation (sticking) of platelets among themselves and the impossibility of accurately counting their number. In this case, the analyzer is not able to isolate these cells and count them accurately, which can lead to a false underestimation of the number of platelets in the blood.If a low platelet count is detected by the analyzer, the laboratory conducts microscopy of the blood smear and gives a conclusion about the presence of platelet aggregates in the smear.

Typical test execution time

Usually the result of a clinical blood test without a formula can be obtained within 1-2 days

Do I need special preparation for the analysis?

No special training required. It is recommended to donate blood no earlier than 3 hours after a meal or on an empty stomach. For infants, it is better to schedule blood sampling before the next feed.

Blood test for hematocrit – prices from 30 rubles. in Moscow, 59 address

Determination of hematocrit is a clinical study that provides information on the ratio of the volume of erythrocytes to the liquid part of the blood. Reflects the level of oxygen exchange between the lungs and body tissues, the degree of hemoconcentration. The study of hematocrit is part of the general blood test. The results are used to diagnose and monitor anemia and polycythemia, to assess the effectiveness of therapeutic measures, in particular blood transfusions, to determine the degree of dehydration, blood thickening or thinning, to determine the need for blood transfusion.Blood sampling for analysis is made from a vein or capillaries. The hematocrit value is determined using standard centrifugation or an automated hematology analyzer. Reference values ​​for men are 39-51%, for women – 35-47%. The analysis time does not exceed a day.

Hematocrit is a laboratory CBC index that reflects the ratio of red blood cell volume to plasma volume. The total is expressed as a percentage and indicates the oxygen-carrying capacity of the blood.An increase in hematocrit is determined in cases where the level of red blood cells in the blood increases or the amount of its liquid part decreases. Such conditions can be triggered by both diseases, such as polycythemia, and physiological conditions. The hematocrit decreases with a decrease in the level of red blood cells and the intake of a large amount of fluid, which increases the volume of plasma. Changes of this nature occur, for example, with blood loss followed by the introduction of saline.

The hematocrit index depends not only on the concentration of erythrocytes, but also on their size. So, with iron deficiency anemia, the size of red blood cells decreases, the hematocrit decreases. In clinical and laboratory practice, to determine this indicator, blood is taken from capillaries, less often from a vein. The result is expressed as a percentage or through a fractional number reflecting the concentration of erythrocytes – l / l. The research procedure is performed in two ways – hematocrit can be determined using standard centrifugation or using a hematological analyzer.The test results are used in general therapeutic practice, in pediatrics, hematology, resuscitation, surgery and other fields of medicine.

Readings

The hematocrit test is part of the complete blood count. The study is carried out during preventive examinations with the aim of early detection of diseases and conditions accompanied by anemia, dehydration, polycythemia, polyglobulia, bleeding (latent). Purposefully, the analysis is prescribed when anemia is suspected, the symptoms of which are weakness, fatigue, headaches and dizziness, pallor and dryness of the skin, brittle nails, and weight loss are objectively determined.The results of hematocrit allow to identify pathology, establish the degree of its severity and track the effectiveness of treatment, but do not indicate its cause.

Other indications for a complete blood count with hematocrit determination include primary and secondary polycythemia. With these diseases, there is an increase in the number of red blood cells in the blood. The hematocrit test is performed in primary polycythemia, when an increase in the concentration of erythrocytes is associated with an increase in their production in the red bone marrow, and in secondary polycythemias associated with diseases of the cardiovascular and respiratory system, kidney pathologies, tumors.Determination of the hematocrit value is used in the diagnosis of dehydration conditions, with bleeding, to resolve the issue of the need for blood transfusion and the introduction of saline, to monitor the effectiveness of these procedures.

A test for hematocrit without a study of the level of red blood cells and their morphology does not provide enough information to detect various hematological disorders. For the diagnosis of anemia and polycythemia, it is necessary to determine several parameters, including the number of erythrocytes, hemoglobin, ferritin, serum iron, transferrin, erythropoietin, and TIBSS.In clinical practice, the study of hematocrit has become widespread due to the cost-effectiveness of the procedure, its reproducibility and availability. These three criteria are especially important in primary, including prophylactic examinations of large groups of patients.

Preparation for analysis and sampling of material

When performing a general blood test with the determination of hematocrit, blood is taken in the morning, on an empty stomach. It is not required to carry out special preparation for the sampling procedure, but it is important to follow several recommendations: the day before the study, you need to refrain from drinking alcohol, after eating, at least 8-12 hours should pass, in half an hour you should stop smoking and physical activity, avoid the influence of stressful factors.During a conversation with a doctor, it is worth informing him about the medications taken so that their possible effect on the hematocrit is taken into account when interpreting the results. There are no restrictions on the use of pure water.

Most often, blood for the study of hematocrit is taken from the ring finger. The procedure is performed using a scarifier pen or lancet. If the doctor recommends taking venous blood, then a puncture of the ulnar vein is performed. After taking, the biomaterial is mixed with an anticoagulant to prevent the clotting process.Laboratories use two methods to determine hematocrit – standard centrifugation and using a hematology analyzer. Their essence lies in the fact that in the process of centrifugation (rapid rotation) heavier and bulkier particles (erythrocytes) settle to the bottom. Then the height of the lower layer is determined and its percentage to the total height of the liquid is calculated. Preparation of the results of this study takes no more than 1 working day.

Normal values ​​

Hematocrit values ​​are expressed as percentages or fractions.The normal values ​​depend on age and gender. For men, they range from 39 to 51%, or from 0.39 to 0.51. In women, the hematocrit is lower, since the blood is updated more often, the normal values ​​are from 35 to 47% or from 0.35 to 0.47. In children, the indicator is determined by age:

• from birth to 7 days – 42-66%;
• from 7 days to 1 month – 36-63%;
• from 1 to 6 months – 30-48%;

90,015 from 6 months to 2 years – 33-39%;

90,015 from 2 to 6 years old – 33-39%;

90,015 from 6 to 12 years old – 35-45%;

90,015 from 12 to 15 years old – 36-49%;

90,015 from 15 to 18 years old – 37-49% for boys, 36-46% for girls.

Physiological change in the hematocrit value is observed during pregnancy, from week 20, the indicators gradually decrease, and before childbirth they increase to normal values. A slight increase in the indicator is possible with oxygen starvation, caused by frequent smoking, stay in high mountain areas.

Increasing value

An increase in the hematocrit may be caused by an increase in the volume of red blood cells in the blood. Changes of this nature are observed in diseases accompanied by an increase in the number or size of red blood cells – with redistribution and true erythrocytosis, primary and secondary polycythemias, compensatory reactions of the cardiovascular system.Another reason for an increase in hematocrit is a decrease in the liquid part of the blood. Dehydration can be caused by burns, peritonitis, profuse diarrhea, vomiting, intestinal obstruction, and hyperhidrosis.

Decrease in value

One of the reasons for the decrease in hematocrit values ​​is erythropenia – a decrease in the number of red blood cells in the blood. The level of red blood cells falls when their production is disrupted in the red bone marrow with anemia, leukemia, prolonged use of cytostatics and anticancer drugs.Sometimes the number of red blood cells in the blood is reduced due to their intense destruction. Such changes occur in hemolytic anemias, hemolytic poisoning, typhoid fever, and malaria. After bleeding and restoration of the circulating blood volume with saline, a temporary decrease in the level of erythrocytes and hematocrit values ​​is also determined.

Another reason for a decrease in hematocrit values ​​is an excessive intake of fluid into the body, which leads to “thinning” of the blood, a change in the percentage of red blood cells and plasma.The cause of overhydration can be water intoxication with circulatory failure, impaired renal function. Another reason for a decrease in hematocrit values ​​is hyperproteinemia or an increase in the level of proteins in the blood. With such changes, binding and water retention in the body occurs. Hyperproteinemia develops in various conditions – with vomiting, diarrhea, acute infections, myeloma, Hodgkin’s lymphoma, paraproteinemic hemoblastosis.