What is the significance of hematocrit and hemoglobin in assessing blood health. How are hematocrit and hemoglobin levels measured. What are the normal ranges for hematocrit and hemoglobin in males and females. How do hematocrit and hemoglobin levels relate to anemia and erythrocytosis.

The Importance of Hematocrit and Hemoglobin in Blood Analysis

Hematocrit and hemoglobin are crucial components in blood analysis, providing essential information about an individual’s blood health. These measurements are fundamental in diagnosing various conditions, including anemia and erythrocytosis. Understanding the relationship between these two factors is vital for healthcare professionals and patients alike.

Defining Hemoglobin and Its Function

Hemoglobin (Hb) is a protein found in red blood cells that plays a critical role in oxygen delivery to tissues throughout the body. Adequate hemoglobin levels are essential for maintaining proper tissue oxygenation. Hemoglobin concentration is typically expressed in grams per deciliter (g/dl) of whole blood.

Normal Hemoglobin Ranges

What are the normal hemoglobin levels for adults? The normal hemoglobin range varies between males and females:

• Males: 14 to 18 g/dl
• Females: 12 to 16 g/dl

When hemoglobin levels fall below these ranges, it may indicate anemia. Conversely, levels above these ranges could suggest erythrocytosis, a condition characterized by an excess of red blood cells.

Understanding Hematocrit

Hematocrit is a measure of the volume of red blood cells in relation to the total blood volume, which includes both red blood cells and plasma. This value is typically expressed as a percentage.

Normal Hematocrit Ranges

What are the normal hematocrit ranges for adults? Similar to hemoglobin, normal hematocrit levels differ between males and females:

• Males: 40 to 54%
• Females: 36 to 48%

These ranges provide valuable insights into an individual’s blood composition and overall health status.

Methods of Measuring Hematocrit and Hemoglobin

Healthcare professionals employ various techniques to measure hematocrit and hemoglobin levels accurately. Understanding these methods is crucial for interpreting test results and ensuring their reliability.

Hematocrit Measurement Techniques

How is hematocrit measured? There are two primary methods for determining hematocrit:

1. Microhematocrit centrifugation: A direct method involving the centrifugation of blood in capillary tubes.
2. Calculated indirectly: Automated cell counters calculate hematocrit by multiplying the red cell count by the mean cell volume (MCV).

Each method has its advantages and potential limitations, which healthcare providers must consider when interpreting results.

Hemoglobin Measurement Techniques

How is hemoglobin measured? Hemoglobin is typically measured using automated cell counters. These devices analyze a sample of EDTA-anticoagulated blood, converting all forms of hemoglobin to cyanomethemoglobin. This colored protein is then measured using a colorimeter, providing an accurate hemoglobin concentration.

Factors Affecting Hematocrit and Hemoglobin Measurements

Several factors can influence hematocrit and hemoglobin measurements, potentially leading to inaccurate results if not properly considered.

Impact of Hydration Status

How does hydration affect hematocrit and hemoglobin readings? Hydration status can significantly impact these measurements:

• Dehydration: Can lead to artificially elevated hematocrit and hemoglobin levels
• Fluid overload: May result in falsely low readings

Healthcare providers must consider a patient’s hydration status when interpreting these values to avoid misdiagnosis.

Influence of Plasma Volume

Both hematocrit and hemoglobin measurements are based on whole blood and are therefore dependent on plasma volume. To assess true red cell mass, independent of plasma volume variations, radionuclide evaluation of red cells and plasma may be necessary in some cases.

The Relationship Between Hematocrit and Hemoglobin

Understanding the relationship between hematocrit and hemoglobin is crucial for comprehensive blood analysis. While these measurements are distinct, they are closely related and often provide complementary information about an individual’s blood health.

Correlation Between Hematocrit and Hemoglobin

How do hematocrit and hemoglobin levels correlate? Generally, there is a strong correlation between hematocrit and hemoglobin levels. In most cases, the hematocrit value is approximately three times the hemoglobin value. This relationship arises from the fact that both measurements reflect the concentration of red blood cells in the blood, albeit in different ways.

Clinical Significance of the Hematocrit-Hemoglobin Relationship

Why is understanding the hematocrit-hemoglobin relationship important clinically? The relationship between these two measurements can provide valuable insights:

• Consistency check: Discrepancies between hematocrit and hemoglobin levels may indicate measurement errors or underlying health issues.
• Diagnostic tool: The ratio of hematocrit to hemoglobin can help identify certain blood disorders or abnormalities.
• Treatment monitoring: Changes in the relationship between these values can indicate the effectiveness of treatments for anemia or other blood disorders.

Healthcare providers use this relationship to ensure the accuracy of blood tests and to gain a more comprehensive understanding of a patient’s blood health.

Anemia and Its Relationship to Hematocrit and Hemoglobin

Anemia is a condition characterized by a deficiency in red blood cells or hemoglobin, leading to reduced oxygen-carrying capacity of the blood. Both hematocrit and hemoglobin measurements play crucial roles in diagnosing and monitoring anemia.

Diagnosing Anemia

How is anemia diagnosed using hematocrit and hemoglobin levels? Anemia is typically diagnosed when hemoglobin or hematocrit levels fall below the normal range for an individual’s age and sex. Healthcare providers often use both measurements to confirm the diagnosis and assess the severity of anemia.

Types of Anemia and Their Impact on Measurements

Different types of anemia can affect hematocrit and hemoglobin levels in various ways:

• Iron-deficiency anemia: Often results in proportional decreases in both hematocrit and hemoglobin.
• Megaloblastic anemia: May cause a more significant decrease in hemoglobin relative to hematocrit.
• Hemolytic anemia: Can lead to rapid decreases in both values due to the destruction of red blood cells.

Understanding these patterns helps healthcare providers determine the underlying cause of anemia and guide appropriate treatment strategies.

Erythrocytosis and Elevated Hematocrit and Hemoglobin Levels

Erythrocytosis, a condition characterized by an excess of red blood cells, results in elevated hematocrit and hemoglobin levels. This condition can have various causes and may require careful management to prevent complications.

Causes of Erythrocytosis

What are the common causes of erythrocytosis? Erythrocytosis can be primary or secondary:

• Primary erythrocytosis: Often caused by genetic mutations affecting red blood cell production.
• Secondary erythrocytosis: Can result from conditions such as chronic lung disease, living at high altitudes, or certain tumors that produce erythropoietin.

Identifying the underlying cause is crucial for appropriate management.

Clinical Implications of Elevated Levels

What are the potential consequences of elevated hematocrit and hemoglobin levels? Erythrocytosis can lead to:

• Increased blood viscosity, potentially impairing circulation
• Increased risk of thrombosis and cardiovascular events
• Symptoms such as headaches, dizziness, and fatigue

Healthcare providers must carefully monitor patients with erythrocytosis and implement appropriate interventions to manage these risks.

Advanced Techniques in Hemoglobin Analysis

While standard hematocrit and hemoglobin measurements provide valuable information, advanced techniques can offer more detailed insights into blood disorders and abnormalities.

Hemoglobin Electrophoresis

What is hemoglobin electrophoresis and how does it work? Hemoglobin electrophoresis is a technique used to separate and identify different types of hemoglobin based on their electrical charge. This method can detect hemoglobin variants that may not be apparent through standard measurements.

Applications of Hemoglobin Electrophoresis

How is hemoglobin electrophoresis used clinically? This technique is particularly useful for:

• Diagnosing hemoglobinopathies such as sickle cell disease and thalassemia
• Identifying carriers of abnormal hemoglobin genes
• Monitoring treatment effectiveness in patients with known hemoglobin disorders

Hemoglobin electrophoresis complements standard hematocrit and hemoglobin measurements, providing a more comprehensive picture of an individual’s blood health.

Understanding the intricacies of hematocrit and hemoglobin measurements is essential for healthcare providers and researchers alike. These fundamental blood parameters offer valuable insights into a wide range of health conditions, from common anemia to rare blood disorders. By leveraging both standard and advanced techniques, medical professionals can ensure accurate diagnoses and effective treatment strategies for patients with blood-related health issues. As research in hematology continues to advance, our understanding of these crucial blood components will undoubtedly deepen, leading to improved patient care and outcomes.

Hemoglobin and Hematocrit – Clinical Methods

Definition

Hemoglobin (Hb) is the protein contained in red blood cells that is responsible for delivery of oxygen to the tissues. To ensure adequate tissue oxygenation, a sufficient hemoglobin level must be maintained. The amount of hemoglobin in whole blood is expressed in grams per deciliter (g/dl). The normal Hb level for males is 14 to 18 g/dl; that for females is 12 to 16 g/dl. When the hemoglobin level is low, the patient has anemia. An erythrocytosis is the consequence of too many red cells; this results in hemoglobin levels above normal.

The hematocrit measures the volume of red blood cells compared to the total blood volume (red blood cells and plasma). The normal hematocrit for men is 40 to 54%; for women it is 36 to 48%. This value can be determined directly by microhematocrit centrifugation or calculated indirectly. Automated cell counters calculate the hematocrit by multiplying the red cell number (in millions/mm³) by the mean cell volume (MCV, in femtoliters). When so assayed, it is subject to the vagaries inherent in obtaining an accurate measurement of the MCV (see Chapter 152).

Both the hemoglobin and the hematocrit are based on whole blood and are therefore dependent on plasma volume. If a patient is severely dehydrated, the hemoglobin and hematocrit will appear higher than if the patient were normovolemic; if the patient is fluid overloaded, they will be lower than their actual level. To assess true red cell mass, independent radionuclide evaluation of the red cells and plasma (by ⁵¹Cr and ¹³¹I respectively) must be performed.

Technique

Hematocrit

If the hematocrit must be determined quickly, as is often the case when a patient hemorrhages, it may be necessary to measure the hematocrit directly without the use of an automated counter. The materials needed are:

• Lancets

• Alcohol prep pads

• Gauze pads

• Microhematocrit tubes (heparinized)

• Sealant (“Seal-Ease,” “Crit-Seal,” etc)

• Microhematocrit centrifuge

• Microhematocrit reader

• If venipuncture is required: tourniquet, syringe, tube containing anticoagulant (EDTA, citrate)

For hematocrits obtained by fingerstick, wipe the fingertip pad of the fourth finger of the nondominant hand with the alcohol prep pad. Make certain the area is allowed to dry. Prick the fingertip with the lancet. Place the hematocrit tube near the incision site and allow the blood to flow via capillary action into the hematocrit tube until it is two-thirds to three-fourths full or to a predesignated mark on the tube. Avoid “milking” the finger if possible; this causes the expression of tissue fluids and may result in a falsely low hematocrit. Always fill at least three tubes. For hematocrits obtained by venipuncture, draw a sample of blood into the tube containing anticoagulant and mix well. Dip the hematocrit tube into the blood and allow the blood to rise to the desired two-thirds to three-quarters level. Because blood cells naturally sediment, a prior thorough mixing of the blood in the tube is necessary to ensure accurate reading.

After cleaning the outside of the hematocrit tubes of excess blood, invert the tube slowly so that the blood migrates just short of the bottom end of the tube. Seal the bottom of the tube with sealant. Make certain that little or no air is interspersed in the column of blood. If the seal is incomplete, leakage will occur during centrifugation and false readings will be obtained.

Place the tubes in a microhematocrit centrifuge and spin for 3 to 5 minutes at high speed. A shorter spin will not allow for complete sedimentation.

Using either a hematocrit reader or any ruled apparatus, measure the length of the column of the packed red cells and divide it by the length of the whole column of blood (cells and plasma), as in . To obtain the hematocrit, multiply this number by 100%. Average all readings obtained from the different microhematocrit tubes.

Figure 151.1

Microhematocrit tube after sedimentation. The hematocrit is a ratio of the packed cells to total volume.

Example: If the column of packed red cells measures 20 mm and the whole blood column measures 50 mm, the hematocrit is 20/50 = 0.4 or (0.4 × 100%) = 40%.

Hemoglobin

Hemoglobin determinations will usually be performed by an automated cell counter from a tube of well-mixed EDTA-anticoagulated blood filled to a predetermined level. In this assay, all forms of hemoglobins are converted to the colored protein cyanomethemoglobin and measured by a colorimeter. An inadequate sample, whether due to insufficient volume or inadequate anticoagulation, may give false readings. If it is necessary to determine the level of anemia quickly, the hematocrit is an easier, more convenient test.

Hemoglobin Electrophoresis

Hemoglobin electrophoresis measures the mobility of hemoglobin in an electric field; it can therefore detect only those abnormalities in hemoglobin that alter the charge. Electrophoretic mobilities are affected by pH and by the medium in which the test is conducted. Screening tests typically use a hemolysate of anticoagulated blood electrophoresed on cellulose acetate at pH 8.6 to 8.8. If necessary, a further electrophoresis in starch gel at pH 6.2 to 6.8 is performed. At that stage, the work will usually be performed by a specialized laboratory.

Hemoglobin electrophoresis will not readily assess situations where there are neutral amino acid substitutions or where the hemoglobin is normal but the constituent chains are not produced in equal numbers (thalassemias). The diagnosis of alpha thalassemia of a mild to moderate degree cannot be made by hemoglobin electrophoresis; the diagnosis of beta thalassemia may be made by inference from an increase in the Hb A₂.

A standard electrophoresis would look like .

Figure 151.2

A standard hemoglobin electrophoresis (cellulose acetate, pH 8.6).

Basic Science

The molecular weight of hemoglobin is approximately 64,500 daltons. Hb is composed of two pairs of dissimilar chains, α and β, each defined by a specific amino acid sequence and incorporating an iron-containing heme group. Two α–β dimers combine to form a hemoglobin tetramer. This allows for the “heme–heme” interaction necessary for effective oxygen uptake (deoxyhemoglobin → oxyhemoglobin) and delivery (oxyhemoglobin → deoxyhemoglobin). The oxygen affinity of hemoglobin is a function of this heme–heme interaction and of pH (Bohr effect), and is a measure of how many hemoglobin molecules have oxygen bound to them for a given level of oxygen tension. In a normal individual the major hemoglobin is Hb A, constituting approximately 97% of the total hemoglobin. Variations and/or amino acid substitutions in these chains exist. Some are deleterious to the normal function of hemoglobin, whereas others may have relatively normal oxygen affinity and stability. Hemoglobins containing different types of chains make up the remainder of the hemoglobin content in red cells (α₂δ₂ = Hb A₂ approximately 2%; α₂γ₂ = Hb F approximately 1%).

Substitutions in the normal hemoglobin amino acid sequence may result in hemoglobins that have different sub-unit interactions and varying affinities for oxygen. For example, a substitution of the sixth amino acid on the beta chain causes Hb S, or sickle hemoglobin. Hb S has a lower oxygen affinity and surrenders its oxygen more readily. Hb F, a normal minor hemoglobin constituent, has a higher oxygen affinity.

If the oxygen dissociation curve is abnormal, the body will adjust the hemoglobin level to ensure adequate oxygen distribution to the tissues. Thus in a rare disease like hemoglobin Hotel Dieu, the difficulty in extracting oxygen from a variant hemoglobin with increased oxygen affinity could result in a lack of oxygen for the tissues (tissue hypoxia) and a compensatory erythrocytosis. The smaller fraction of oxygen released from the hemoglobin is thereby offset by the increased number of hemoglobin molecules. Similarly, in sickle cell anemia, the decreased oxygen affinity allows these patients more tissue oxygen at any given hemoglobin level.

Clinical Significance

Many anemias are detected by routine laboratory screening performed before the patient is symptomatic. When the patient does have symptoms from an abnormality in the hemoglobin level, the symptoms are often a nonspecific weakness or fatigue. The only finding on physical examination may be pallor; additional changes in the nail beds (such as spooning), glossitis (red tongue), or hepatosplenomegaly (enlarged liver or spleen) may give a clue to the etiology of the anemia. Symptoms are usually related to the level of hemoglobin, its abruptness of onset and its duration. A patient with pernicious anemia may feel well at the same level of hemoglobin that would cause severe weakness in a patient with acute gastrointestinal hemorrhage. This is due to volume compensation by plasma and shifts in the oxygen dissociation curve which occur over time.

When first confronted with an abnormal hemoglobin or hematocrit level, the next step is to assess the red cell indices (see Chapter 152), peripheral smear (Chapter 155), and the reticulocyte count (Chapter 156) in light of the patient’s history and physical examination.

References

1. Adamson JW, Finch CA. Hemoglobin function, oxygen affinity and erythropoietin. Annu Rev Physiol. 1975;37:351. [PubMed: 235878]

2. Bunn HF. Hemoglobin I. Structure and function. In: Beck WS, Hematology. Cambridge, MA: MIT Press, 1981;129.

3. Scott AF. et al. The molecular basis of hemoglobin. Am J Hum Genet. 1981;33:129. [PMC free article: PMC1684884] [PubMed: 6258429]

4. Wallerstein RO. Laboratory evaluation of anemia. West J Med. 1987;146:443. [PMC free article: PMC1307333] [PubMed: 3577135]

Hemoglobin and Hematocrit – Clinical Methods

Definition

Hemoglobin (Hb) is the protein contained in red blood cells that is responsible for delivery of oxygen to the tissues. To ensure adequate tissue oxygenation, a sufficient hemoglobin level must be maintained. The amount of hemoglobin in whole blood is expressed in grams per deciliter (g/dl). The normal Hb level for males is 14 to 18 g/dl; that for females is 12 to 16 g/dl. When the hemoglobin level is low, the patient has anemia. An erythrocytosis is the consequence of too many red cells; this results in hemoglobin levels above normal.

The hematocrit measures the volume of red blood cells compared to the total blood volume (red blood cells and plasma). The normal hematocrit for men is 40 to 54%; for women it is 36 to 48%. This value can be determined directly by microhematocrit centrifugation or calculated indirectly. Automated cell counters calculate the hematocrit by multiplying the red cell number (in millions/mm³) by the mean cell volume (MCV, in femtoliters). When so assayed, it is subject to the vagaries inherent in obtaining an accurate measurement of the MCV (see Chapter 152).

Both the hemoglobin and the hematocrit are based on whole blood and are therefore dependent on plasma volume. If a patient is severely dehydrated, the hemoglobin and hematocrit will appear higher than if the patient were normovolemic; if the patient is fluid overloaded, they will be lower than their actual level. To assess true red cell mass, independent radionuclide evaluation of the red cells and plasma (by ⁵¹Cr and ¹³¹I respectively) must be performed.

Technique

Hematocrit

If the hematocrit must be determined quickly, as is often the case when a patient hemorrhages, it may be necessary to measure the hematocrit directly without the use of an automated counter. The materials needed are:

• Lancets

• Alcohol prep pads

• Gauze pads

• Microhematocrit tubes (heparinized)

• Sealant (“Seal-Ease,” “Crit-Seal,” etc)

• Microhematocrit centrifuge

• Microhematocrit reader

• If venipuncture is required: tourniquet, syringe, tube containing anticoagulant (EDTA, citrate)

For hematocrits obtained by fingerstick, wipe the fingertip pad of the fourth finger of the nondominant hand with the alcohol prep pad. Make certain the area is allowed to dry. Prick the fingertip with the lancet. Place the hematocrit tube near the incision site and allow the blood to flow via capillary action into the hematocrit tube until it is two-thirds to three-fourths full or to a predesignated mark on the tube. Avoid “milking” the finger if possible; this causes the expression of tissue fluids and may result in a falsely low hematocrit. Always fill at least three tubes. For hematocrits obtained by venipuncture, draw a sample of blood into the tube containing anticoagulant and mix well. Dip the hematocrit tube into the blood and allow the blood to rise to the desired two-thirds to three-quarters level. Because blood cells naturally sediment, a prior thorough mixing of the blood in the tube is necessary to ensure accurate reading.

After cleaning the outside of the hematocrit tubes of excess blood, invert the tube slowly so that the blood migrates just short of the bottom end of the tube. Seal the bottom of the tube with sealant. Make certain that little or no air is interspersed in the column of blood. If the seal is incomplete, leakage will occur during centrifugation and false readings will be obtained.

Place the tubes in a microhematocrit centrifuge and spin for 3 to 5 minutes at high speed. A shorter spin will not allow for complete sedimentation.

Using either a hematocrit reader or any ruled apparatus, measure the length of the column of the packed red cells and divide it by the length of the whole column of blood (cells and plasma), as in . To obtain the hematocrit, multiply this number by 100%. Average all readings obtained from the different microhematocrit tubes.

Figure 151.1

Microhematocrit tube after sedimentation. The hematocrit is a ratio of the packed cells to total volume.

Example: If the column of packed red cells measures 20 mm and the whole blood column measures 50 mm, the hematocrit is 20/50 = 0.4 or (0.4 × 100%) = 40%.

Hemoglobin

Hemoglobin determinations will usually be performed by an automated cell counter from a tube of well-mixed EDTA-anticoagulated blood filled to a predetermined level. In this assay, all forms of hemoglobins are converted to the colored protein cyanomethemoglobin and measured by a colorimeter. An inadequate sample, whether due to insufficient volume or inadequate anticoagulation, may give false readings. If it is necessary to determine the level of anemia quickly, the hematocrit is an easier, more convenient test.

Hemoglobin Electrophoresis

Hemoglobin electrophoresis measures the mobility of hemoglobin in an electric field; it can therefore detect only those abnormalities in hemoglobin that alter the charge. Electrophoretic mobilities are affected by pH and by the medium in which the test is conducted. Screening tests typically use a hemolysate of anticoagulated blood electrophoresed on cellulose acetate at pH 8.6 to 8.8. If necessary, a further electrophoresis in starch gel at pH 6.2 to 6.8 is performed. At that stage, the work will usually be performed by a specialized laboratory.

Hemoglobin electrophoresis will not readily assess situations where there are neutral amino acid substitutions or where the hemoglobin is normal but the constituent chains are not produced in equal numbers (thalassemias). The diagnosis of alpha thalassemia of a mild to moderate degree cannot be made by hemoglobin electrophoresis; the diagnosis of beta thalassemia may be made by inference from an increase in the Hb A₂.

A standard electrophoresis would look like .

Figure 151.2

A standard hemoglobin electrophoresis (cellulose acetate, pH 8.6).

Basic Science

The molecular weight of hemoglobin is approximately 64,500 daltons. Hb is composed of two pairs of dissimilar chains, α and β, each defined by a specific amino acid sequence and incorporating an iron-containing heme group. Two α–β dimers combine to form a hemoglobin tetramer. This allows for the “heme–heme” interaction necessary for effective oxygen uptake (deoxyhemoglobin → oxyhemoglobin) and delivery (oxyhemoglobin → deoxyhemoglobin). The oxygen affinity of hemoglobin is a function of this heme–heme interaction and of pH (Bohr effect), and is a measure of how many hemoglobin molecules have oxygen bound to them for a given level of oxygen tension. In a normal individual the major hemoglobin is Hb A, constituting approximately 97% of the total hemoglobin. Variations and/or amino acid substitutions in these chains exist. Some are deleterious to the normal function of hemoglobin, whereas others may have relatively normal oxygen affinity and stability. Hemoglobins containing different types of chains make up the remainder of the hemoglobin content in red cells (α₂δ₂ = Hb A₂ approximately 2%; α₂γ₂ = Hb F approximately 1%).

Substitutions in the normal hemoglobin amino acid sequence may result in hemoglobins that have different sub-unit interactions and varying affinities for oxygen. For example, a substitution of the sixth amino acid on the beta chain causes Hb S, or sickle hemoglobin. Hb S has a lower oxygen affinity and surrenders its oxygen more readily. Hb F, a normal minor hemoglobin constituent, has a higher oxygen affinity.

If the oxygen dissociation curve is abnormal, the body will adjust the hemoglobin level to ensure adequate oxygen distribution to the tissues. Thus in a rare disease like hemoglobin Hotel Dieu, the difficulty in extracting oxygen from a variant hemoglobin with increased oxygen affinity could result in a lack of oxygen for the tissues (tissue hypoxia) and a compensatory erythrocytosis. The smaller fraction of oxygen released from the hemoglobin is thereby offset by the increased number of hemoglobin molecules. Similarly, in sickle cell anemia, the decreased oxygen affinity allows these patients more tissue oxygen at any given hemoglobin level.

Clinical Significance

Many anemias are detected by routine laboratory screening performed before the patient is symptomatic. When the patient does have symptoms from an abnormality in the hemoglobin level, the symptoms are often a nonspecific weakness or fatigue. The only finding on physical examination may be pallor; additional changes in the nail beds (such as spooning), glossitis (red tongue), or hepatosplenomegaly (enlarged liver or spleen) may give a clue to the etiology of the anemia. Symptoms are usually related to the level of hemoglobin, its abruptness of onset and its duration. A patient with pernicious anemia may feel well at the same level of hemoglobin that would cause severe weakness in a patient with acute gastrointestinal hemorrhage. This is due to volume compensation by plasma and shifts in the oxygen dissociation curve which occur over time.

When first confronted with an abnormal hemoglobin or hematocrit level, the next step is to assess the red cell indices (see Chapter 152), peripheral smear (Chapter 155), and the reticulocyte count (Chapter 156) in light of the patient’s history and physical examination.

References

1. Adamson JW, Finch CA. Hemoglobin function, oxygen affinity and erythropoietin. Annu Rev Physiol. 1975;37:351. [PubMed: 235878]

2. Bunn HF. Hemoglobin I. Structure and function. In: Beck WS, Hematology. Cambridge, MA: MIT Press, 1981;129.

3. Scott AF. et al. The molecular basis of hemoglobin. Am J Hum Genet. 1981;33:129. [PMC free article: PMC1684884] [PubMed: 6258429]

4. Wallerstein RO. Laboratory evaluation of anemia. West J Med. 1987;146:443. [PMC free article: PMC1307333] [PubMed: 3577135]

Prothrombin time, INR, prothrombin according to Quick

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Prothrombin time – the time required for plasma to clot when calcium and tissue factor are added. Method reproduces external pathway of blood coagulation with evaluation of the so-called prothrombin complex – factors VII, X, prothrombin. Vitamin K-dependent clotting factors are involved in the extrinsic pathway, so PT is used to evaluate therapy with indirect anticoagulants .

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  Blood coagulation system. Laboratory diagnosis of hemostasis disorders. Interpretation of results. Features of hemostasis during pregnancy. Molecular genetic analyses. platelet function.

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