What has your blood sugar been up to lately? Get an A1C test to find out your average levels—important to know if you’re at risk for prediabetes or type 2 diabetes, or if you’re managing diabetes.

Understanding the A1C Test

The A1C test, also known as the hemoglobin A1C or HbA1c test, is a simple blood test that measures your average blood sugar levels over the past 3 months. It’s one of the commonly used tests to diagnose prediabetes and diabetes, and is also the main test to help you and your health care team manage your diabetes. Higher A1C levels are linked to diabetes complications, so reaching and maintaining your individual A1C goal is really important if you have diabetes.

What Does the A1C Test Measure?

When sugar enters your bloodstream, it attaches to hemoglobin, a protein in your red blood cells. Everybody has some sugar attached to their hemoglobin, but people with higher blood sugar levels have more. The A1C test measures the percentage of your red blood cells that have sugar-coated hemoglobin.

Who Should Get an A1C Test, and When?

Testing for Diabetes or Prediabetes

Get a baseline A1C test if you’re an adult over age 45—or if you’re under 45, are overweight, and have one or more risk factors for prediabetes or type 2 diabetes. If your result is normal but you’re over 45, have risk factors, or have ever had gestational diabetes, repeat the A1C test every 3 years.

If your result shows you have prediabetes, talk to your doctor about taking steps now to improve your health and lower your risk for type 2 diabetes. Repeat the A1C test as often as your doctor recommends, usually every 1 to 2 years.

If you don’t have symptoms but your result shows you have prediabetes or diabetes, get a second test on a different day to confirm the result.

If your test shows you have diabetes, ask your doctor to refer you to diabetes self-management education and support services so you can have the best start in managing your diabetes.

Managing Diabetes

If you have diabetes, get an A1C test at least twice a year, more often if your medicine changes or if you have other health conditions. Talk to your doctor about how often is right for you.

How to Prepare for Your A1C Test

The test is done in a doctor’s office or a lab using a sample of blood from a finger stick or from your arm. You don’t need to do anything special to prepare for your A1C test. However, ask your doctor if other tests will be done at the same time and if you need to prepare for them.

Understanding Your A1C Result

Diagnosing Prediabetes or Diabetes

A normal A1C level is below 5.7%, a level of 5.7% to 6.4% indicates prediabetes, and a level of 6.5% or more indicates diabetes. Within the 5.7% to 6.4% prediabetes range, the higher your A1C, the greater your risk is for developing type 2 diabetes.

Managing Diabetes

Your A1C result can also be reported as estimated average glucose (eAG), the same numbers (mg/dL) you’re used to seeing on your blood sugar meter:

• A1C 7% = eAG 154 mg/dL
• A1C 8% = eAG 183 mg/dL
• A1C 9% = eAG 212 mg/dL
• A1C 10% = eAG 240 mg/dL

What Can Affect Your A1C Result?

Get your A1C tested in addition to—not instead of—regular blood sugar self-testing if you have diabetes. Several factors can falsely increase or decrease your A1C result, including:

• Kidney failure, liver disease, or severe anemia.
• A less common type of hemoglobin that people of African, Mediterranean, or Southeast Asian descent and people with certain blood disorders (such as sickle cell anemia or thalassemia) may have.
• Certain medicines, including opioids and some HIV medications.
• Blood loss or blood transfusions.
• Early or late pregnancy.

Let your doctor know if any of these factors apply to you, and ask if you need additional tests to find out.

Setting Your A1C Goal

The goal for most people with diabetes is 7% or less. However, your personal goal will depend on many things such as your age and any other medical conditions. Work with your doctor to set your own individual A1C goal.

Younger people have more years with diabetes ahead, so their goal may be lower to reduce the risk of complications, unless they often have hypoglycemia (low blood sugar, or a “low”). People who are older, have severe lows, or have other serious health problems may have a higher goal.

A1C: Just Part of the Toolkit

A1C is an important tool for managing diabetes, but it doesn’t replace regular blood sugar testing at home. Blood sugar goes up and down throughout the day and night, which isn’t captured by your A1C. Two people can have the same A1C, one with steady blood sugar levels and the other with high and low swings.

If you’re reaching your A1C goal but having symptoms of highs or lows, check your blood sugar more often and at different times of day. Keep track and share the results with your doctor so you can make changes to your treatment plan if needed.

All About Your A1C

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What has your blood sugar been up to lately? Get an A1C test to find out your average levels—important to know if you’re at risk for prediabetes or type 2 diabetes, or if you’re managing diabetes.

The A1C test—also known as the hemoglobin A1C or HbA1c test—is a simple blood test that measures your average blood sugar levels over the past 3 months. It’s one of the commonly used tests to diagnose prediabetes and diabetes, and is also the main test to help you and your health care team manage your diabetes. Higher A1C levels are linked to diabetes complications, so reaching and maintaining your individual A1C goal is really important if you have diabetes.

What Does the A1C Test Measure?

When sugar enters your bloodstream, it attaches to hemoglobin, a protein in your red blood cells. Everybody has some sugar attached to their hemoglobin, but people with higher blood sugar levels have more. The A1C test measures the percentage of your red blood cells that have sugar-coated hemoglobin.

Who Should Get an A1C Test, and When?

Testing for diabetes or prediabetes:
Get a baseline A1C test if you’re an adult over age 45—or if you’re under 45, are overweight, and have one or more risk factors for prediabetes or type 2 diabetes:

• If your result is normal but you’re over 45, have risk factors, or have ever had gestational diabetes, repeat the A1C test every 3 years.
• If your result shows you have prediabetes, talk to your doctor about taking steps now to improve your health and lower your risk for type 2 diabetes. Repeat the A1C test as often as your doctor recommends, usually every 1 to 2 years.
• If you don’t have symptoms but your result shows you have prediabetes or diabetes, get a second test on a different day to confirm the result.
• If your test shows you have diabetes, ask your doctor to refer you to diabetes self-management education and support services so you can have the best start in managing your diabetes.

Managing diabetes:
If you have diabetes, get an A1C test at least twice a year, more often if your medicine changes or if you have other health conditions. Talk to your doctor about how often is right for you.

How to Prepare for Your A1C Test

The test is done in a doctor’s office or a lab using a sample of blood from a finger stick or from your arm. You don’t need to do anything special to prepare for your A1C test. However, ask your doctor if other tests will be done at the same time and if you need to prepare for them.

Your A1C Result

Diagnosing Prediabetes or Diabetes

A normal A1C level is below 5.7%, a level of 5. 7% to 6.4% indicates prediabetes, and a level of 6.5% or more indicates diabetes. Within the 5.7% to 6.4% prediabetes range, the higher your A1C, the greater your risk is for developing type 2 diabetes.

Managing Diabetes
Your A1C result can also be reported as estimated average glucose (eAG), the same numbers (mg/dL) you’re used to seeing on your blood sugar meter:

What Can Affect Your A1C Result?

Get your A1C tested in addition to—not instead of—regular blood sugar self-testing if you have diabetes.

Several factors can falsely increase or decrease your A1C result, including:

• Kidney failure, liver disease, or severe anemia.
• A less common type of hemoglobin that people of African, Mediterranean, or Southeast Asian descent and people with certain blood disorders (such as sickle cell anemia or thalassemia) may have.
• Certain medicines, including opioids and some HIV medications.
• Blood loss or blood transfusions.
• Early or late pregnancy.

Let your doctor know if any of these factors apply to you, and ask if you need additional tests to find out.

Your A1C Goal

The goal for most people with diabetes is 7% or less. However, your personal goal will depend on many things such as your age and any other medical conditions. Work with your doctor to set your own individual A1C goal.

Younger people have more years with diabetes ahead, so their goal may be lower to reduce the risk of complications, unless they often have hypoglycemia (low blood sugar, or a “low”). People who are older, have severe lows, or have other serious health problems may have a higher goal.

A1C: Just Part of the Toolkit

A1C is an important tool for managing diabetes, but it doesn’t replace regular blood sugar testing at home. Blood sugar goes up and down throughout the day and night, which isn’t captured by your A1C. Two people can have the same A1C, one with steady blood sugar levels and the other with high and low swings.

If you’re reaching your A1C goal but having symptoms of highs or lows, check your blood sugar more often and at different times of day. Keep track and share the results with your doctor so you can make changes to your treatment plan if needed.

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A1C and eAG | ADA

What is the difference between eAG and the average on my monitor?  

The A1C test gives you a picture of your average blood glucose (blood sugar) control for the past two to three months. The results give you and your diabetes care team a good idea of how well your diabetes treatment plan is working.

In some ways, the A1C test is like a baseball player’s season batting average: it tells you about a person’s overall success. Neither a single day’s blood test results nor a single game’s batting record gives the same big picture.

The A1C test can help you manage your diabetes by:

• Confirming self-testing results or blood test results by the doctor.
• Judging whether a treatment plan is working.
• Showing you how healthy choices can make a difference in diabetes control.

Your health care provider may report your A1C test result as eAG, or “average glucose,” which directly correlates to your A1C. eAG may help you understand your A1C value because eAG is reported as the same unit (mg/dL) that you see through self-monitoring on your meter or continuous glucose monitor (CGM).

The difference between eAG/A1C and the average on your monitor

The catch is that eAG/A1C is not the same average glucose level as the average of the readings on your meter.

Monitoring measures your blood glucose at a moment in time, whereas eAG/A1C represent an average of your glucose levels 24 hours a day, including times when people are less likely to check their blood sugar (for example, post-meal periods of higher blood sugar).

People with diabetes are also more likely to check their blood glucose more often when they are low (for example, first thing in the morning and before meals), so the average of readings on their meter is likely to be lower than their eAG.

So, how does A1C work?

Hemoglobin, a protein that links up with glucose, is found inside red blood cells. Its job is to carry oxygen from the lungs to all the cells of the body. Glucose enters your red blood cells and links up (or glycates) with molecules of hemoglobin. The more glucose in your blood, the more hemoglobin gets glycated. By measuring the percentage of A1C in the blood, you get an overview of your average blood glucose control for the past few months. Your doctor should measure your A1C level at least twice a year.

What’s your number?

The American Diabetes Association suggests an A1C of 7 percent for nonpregnant adults, which is an eAG of 154 mg/dl, but more or less stringent glycemic goals may be appropriate for each individual.

A1C to eAG

eAG to A1C

Enter your A1C percentage:

Your A1C target is your own

You are unique and you need advice based on your own set of circumstances. If someone who hears your A1C says, “Your A1C level should be x, y, or z.” Your response can be: “I am working with my doctor on reaching my own safe diabetes target, and it has been customized for my condition.” 

A1C targets often change over time, sometimes decreasing and sometimes increasing. It all depends on the person and circumstances. Don’t compare yourself or your child to others. Know your goals and be clear, persistent and honest in your approach to managing diabetes. 

Your diabetes care team is here to help

Never avoid going to see your health care team because you feel like a “failure” or are afraid of disappointing them. The members of your diabetes care team are your coaches. They understand there are multiple life challenges that influence diabetes each day and night. Life is always changing, and you/your child will need support along the way. This is all part of the process of living with diabetes.

Human Hearing Characteristics – Hearing Thresholds and Ranges

Hearing threshold

The human hearing threshold is the minimum level of sound that a person can perceive. This characteristic is one of the main ones.

Hearing sensitivity depends on the hearing threshold: the lower the hearing threshold, the higher the hearing sensitivity, and vice versa. The range of the highest sound sensitivity is from 1000 to 4000 Hz. It is in this interval that information about speech signals is located. Hearing thresholds at 200 Hz are 35 dB higher and at 100 Hz are 60 dB higher than hearing thresholds at 1000 Hz.

The normal hearing threshold is between -10dB and +10dB. In cases of hearing impairment, the thresholds can be different – from 20 to 120 dB.

Source: introduction to audiology and hearing aid I.V. Queen

Discomfort threshold

The threshold of discomfort is the level of sound that causes discomfort in a person. The norm is 100-110 dB, and it depends not only on the state of the hearing organ, but also on the excitability of the nervous system as a whole. In patients with hearing impairments, the discomfort threshold is usually greater than 110 dB. However, many people with sensorineural hearing loss have thresholds of discomfort that are the same as those of people with normal hearing or lower – a phenomenon called recruitment, or the “amplifying loudness phenomenon.”

Pain threshold

Pain in the organ of hearing, as a rule, causes a sound of 130-140 dB. In addition, one should distinguish between the threshold of touch and the pain threshold – in the first case, a person feels only pressure on the eardrum (130 dB), in the second – already pain sensations (140 dB). The threshold of discomfort for people with hearing impairment may differ from the norm, but the pain threshold is always the same for everyone.

Hearing frequency range

The ability to perceive sounds in the frequency range from 20 to 20,000 Hz is considered the norm for a person. Sounds with a frequency above 20,000 Hz are called ultrasonics, and those below 20 Hz are called infrasounds. A person can perceive ultrasound only if its source is applied to the bones of the skull – this property is sometimes used in the diagnosis of hearing impairment.

Source: introduction to audiology and hearing aid I.V. Queen

Approaching the study of hearing, the sound frequency range is conventionally divided:

to low frequencies – up to 500 Hz;

at medium frequencies – 500-3000 Hz;

to high frequencies – 3000–8000 Hz;

for ultra-high frequencies – above 8000 Hz

Hearing dynamic range

The dynamic range of hearing is the total amount of sound levels that a person is able to perceive, normally it is 130 dB. The difference between the quietest and loudest sound perceived by the human ear (up to palpable or pain thresholds) is large – the latter is higher by about 10 ¹³ times.

In audiology, the dynamic range of hearing is the range from a person’s hearing threshold to their discomfort threshold.

Both dynamic and frequency range can be different for people with hearing loss.

Differential hearing threshold

The minimum differences in frequency, intensity, or duration of a sound perceived by human hearing are called the differential hearing threshold.

It is the ability to detect minimal differences between sounds that allows us to perceive speech. The intensity and frequency of the differential hearing threshold depends on the duration, level and frequency of the sound. The norm for a person is 1–1.5 dB in intensity at frequencies of 500–4000 Hz at a sound level of 40 dB.

The reason for the poor perception of speech by people with hearing impairment lies in the increase in their differential hearing threshold – they simply cease to perceive small differences between speech sounds.

Binaural hearing

The ability of a person to perceive sound with two ears and process the received signals in the corresponding symmetrical auditory centers of the brain is called binaural hearing. This property provides the so-called process of binaural fusion – this is when sounds of different characteristics entering the right and left ears of a person are perceived by the human auditory system as a single and integral auditory image. In addition, by comparing the sounds entering the right and left ears, the auditory system determines where the sound source is.

It is binaural hearing that allows us to perceive speech in noisy environments – the so-called “binaural release from disguise” effect occurs.

Article about binaural prosthetics.

Source: introduction to audiology and hearing aid I.V. Queen

Hearing adaptation

Like other sensory systems of the human body, the auditory system is able to adapt to external conditions. This is manifested in a temporary decrease in sensitivity due to an increase in hearing thresholds in cases of excessive sound exposure. With this ability, the auditory system protects itself from damage.

The hearing threshold is raised by any exposure to sound that exceeds this threshold by 10-20 dB. In cases of short-term exposure to sound no higher than 80-90 dB, and the increase in the threshold will be short-term. With more intense exposure, the increase in hearing thresholds will last longer – up to several minutes. After the cessation of sound exposure, the hearing thresholds gradually return to their original state.

Analysis norms. Analysis decoding. Reference values, interval. “Norm” and “pathology” in laboratory diagnostics.

This article describes what the test norms are, how tests are deciphered, why it is not modern to say “norm”, and what are the reference values ​​​​and the reference interval.

Standards for interpretation of tests.

Concept of reference values ​​and reference interval.

The information obtained in the course of laboratory analysis is based on the detection and / or measurement in clinical samples (biomaterial) of patients of certain components – analytes, functionally or structurally related to a particular organ or system of human organs. The most important component of any laboratory research is the interpretation of its result. Establishing the difference between the norm of analyzes and pathology plays a key role in assessing the data obtained. In practice, this is not difficult to do with a clear deviation of laboratory parameters from the values ​​taken as the norm. However, it is not always easy to divide most of the results of laboratory tests into “normal” and “pathology”, and therefore, in order to interpret them, a comparison of the data obtained with the indicators established as the norm is required.

Normal test values ​​(norm) are values ​​found in healthy people. However, in the groups of the latter, they can have different values, that is, the norm is individual. This is due both to the individual physiological characteristics of the human body (characteristics of metabolism, circadian biological rhythms, the functional state of certain organs and their systems), and differences in gender, age, and physiological state. For example, during pregnancy, many biochemical parameters of a woman’s body change, therefore, appropriate individual norms are determined for pregnant women.

Normal laboratory values ​​are determined in experimental clinical studies based on the results of measurements of the analyte under investigation in a large population of healthy people, specially selected and grouped by age, sex or other biological and other factors. The data obtained lead to the mean value, taking into account the statistically possible standard deviations of its value. In this regard, it is more correct to speak not about the “norm” of a laboratory indicator, but about the range in which normal (reference) values ​​are located. Therefore, at present, the term “norm”, which has already become familiar in assessing the results of a laboratory study, is used less often. Instead, they talk about reference (reference) values ​​ and the results obtained for a particular patient are compared with the so-called reference interval (range) . This term is more accurate, because it gives an idea of ​​the lower and upper limits of the norm of a laboratory indicator, possible, statistically significant limits of fluctuation (deviation) of its value and, at the same time, emphasizes the relativity of these data, the possibility of applying only to a certain group of people.

Explanation of analyzes. Norm or pathology?

When establishing the reference range, mathematical and statistical approaches are used, according to which the values ​​of the results of laboratory studies of a certain analyte of 95% of healthy people fall within the established interval. Accordingly, for 5% – the values ​​of the analyzed indicators are outside the established range. In other words, in 5% of cases in healthy people, “abnormal” laboratory parameters are detected, which should be taken into account when deciphering the analysis. This is explained by a number of reasons.

First, the division of the biological population of people into “sick” and “healthy” according to many laboratory parameters is very conditional. Being statistical data, the limits of normal laboratory values ​​may vary. Therefore, it happens that in healthy people certain indicators that are “normal” for them are not ultimately “normal” for most others, and therefore do not fall into the range of generally accepted reference values. In this case, the limits of the reference range cannot serve as absolute indicators of health or disease.

On the other hand, often the disease develops imperceptibly, manifesting itself as a gradual transition from small deviations in laboratory parameters to higher values ​​as dysfunction increases and the severity of the disease progresses. In this regard, when deciphering the analyzes in interpreting the results of laboratory tests, it becomes very important for the clinician to assess the dynamics of changes in a particular laboratory indicator in a particular patient. In doubtful cases, the main criterion for the presence or absence of a disease is the clinical symptomatology or the degree of its severity. In the presence of symptoms of the disease, additional laboratory tests are used for diagnosis using highly sensitive and specific tests that most pronouncedly change their values ​​against the background of the suspected disease.

Secondly, “healthy” and “sick” people actually belong to two different populations, and when these populations are mixed together, it is almost impossible to recognize each of them in the total mass. In addition, in different patients, the same indicator can not only take on different values, but also overlap the values ​​of this indicator in healthy people. Moreover, for different indicators, different diseases, different groups of patients, the value of such a “cross” can vary greatly: from too small, which can be neglected, to very significant, when a special approach and careful analysis of all data is required to classify the result as “normal” or “pathological”. The latter is extremely important to take into account when evaluating the results of laboratory tests, since in this case not all values ​​that are outside the normal range will indicate the presence of pathology. The range of values ​​in which the laboratory parameters of “sick” and “healthy” individuals overlap is called the zone of uncertainty, or the “gray zone”. It exists for a range of laboratory procedures, but is most commonly found in enzyme immunoassay results. If the result falls into the “gray zone”, it cannot be unequivocally regarded either as a norm or as a pathology and is considered as doubtful. In such a case, the patient is usually advised to repeat the diagnostic study 2 to 4 weeks after receiving an indeterminate result.

And, finally, not always an indicator lying in the reference interval can be considered normal, since the range of many of them is quite wide. For example, the normal value of hematocrit (Ht) in men varies from 42 to 52%. Massive blood loss can lead to a drop in this indicator from 52 to 42%, while the value of 42% remains within the range of reference values, and therefore may not cause alarm for doctors. However, in a certain situation, for a particular patient, such a decrease in hematocrit can be not only clinically significant, but also critical.

Therefore, results within the reference range are not always normal. And, on the contrary, the results that go beyond the reference values ​​are not always pathology, but only a significant prognostic sign that can signal a possible pathological process. In this regard, in laboratory diagnostics, the approach is becoming more widespread, when the most significant and adequate reference values ​​for each individual patient should be considered stable results of his laboratory studies obtained over several years. Already at present, experts around the world are inclined to believe that it is necessary to “lower” the significance of reference intervals, moving away from interpreting them as some kind of “absolute” criterion for evaluating a laboratory result. This circumstance in no way reduces the importance of laboratory research. They remain the most important tool for diagnosing pathological conditions, monitoring the course of diseases, identifying the preclinical stage of diseases during screening examinations, and also largely determine the further tactics of diagnostic procedures and treatment decisions. However, this approach directs the clinician to a more cautious use of reference values ​​in the assessment of “normal” and “pathological” results, indicating the need for their interpretation, taking into account possible biological variation in the population, taking into account the data of the clinical picture and other types of studies in the aggregate, and as well as those factors that may influence the results of laboratory tests.

Reference ranges

Reference values ​​are currently established for many laboratory parameters. The results of some types of research are given to the patient in the form of “yes” or “no”. This type of research is qualitative. For example, a positive result for antibodies to a specific infection indicates the presence of these antibodies in the patient’s blood and may indicate infection. In the case when the study was quantitative, the result is issued as a numerical value, indicating on the form the units of measurement and the corresponding reference range. For example, the results of a biochemical study to determine the level of C-reactive protein (CRP), which is a marker of inflammation, may look like this: 0.4 mg / l, reference values: 0 – 6 mg / l. From the above example, it can be seen that the result obtained is within the established reference range. For most laboratory parameters, the range of reference values ​​is indicated taking into account the patient’s gender and / or his belonging to a certain age group. For example, the reference values ​​​​of serum creatinine for children under 1 year old are 18 – 35 µmol / l, for children from one to 14 years old – 27 – 62 µmol / l, and for people over 14 years old – 62 – 115 µmol / l for male and 53 – 97 µmol/l for females.

The influence of age and sex on the range of reference values ​​is significant for many laboratory tests. For example, the concentration of alkaline phosphatase, a key enzyme secreted by bone tissue cells, increases in proportion to the rate of formation of new bone cells. Therefore, in children and adolescents, a high level of this enzyme is not only normal, but also desirable, since it is associated with the active formation and growth of bones. On the contrary, a high level of alkaline phosphatase in an adult may indicate developing osteoporosis, metastases of bone tumors, or other pathological processes. The exception is pregnant women, who are characterized by a physiological increase in the activity of this enzyme, especially in the third trimester of pregnancy.

Why can reference ranges vary from laboratory to laboratory?

Different diagnostic laboratories use different types of laboratory equipment to perform analysis, for example, biochemical and immunochemical analyzers, the range of which is currently very wide, work on reagents from different manufacturers, and in addition, they may use different research methods than other laboratories . In this regard, each laboratory indicates on the form of results its ranges of reference values, when establishing which, of course, it is guided by generally accepted standards, but taking into account the individual characteristics of its work: the specifics of the equipment used, the methods of analysis used and units of measurement. That is why the ranges of reference values ​​for the same laboratory test may vary according to the data of different diagnostic laboratories, and there is no such thing as a “single” reference range. When evaluating the results of laboratory tests, the attending physician should first of all refer to the range of reference values ​​indicated on the form of the laboratory in which the analysis was performed. In order for the results to be interpreted correctly and comparable, especially in the case of repeated studies, for example, when monitoring therapy or dynamic assessment of the patient’s condition, it is advisable to conduct studies using the same method, in the same laboratory and, if possible, ceteris paribus.

Factors affecting laboratory results

Modern methods of clinical laboratory research are characterized by high sensitivity and specificity, and therefore their results, reflecting the patient’s health status, can serve as the basis for making important clinical decisions by the attending physician. At the same time, both clinicians and patients should understand that there are a number of non-pathological factors that can, to a certain extent, influence the results of laboratory tests, distorting the objective picture of the patient’s health. Some of these factors can only be controlled by the efforts of laboratory specialists, minimizing their possible negative impact on the final result of the laboratory study. Among such factors, for example, the conditions and method of taking biological material, delivery and storage of samples, the correctness of their identification in the laboratory. However, to minimize the negative impact of many other factors that affect the accuracy of the final result of a laboratory test, only the patient himself or his attending physician, who must inform the patient about the correct preparation for a certain type of laboratory test, can. Compliance with the doctor’s instructions will allow the analysis to be as close as possible to the general requirements, for example, the need to donate blood on an empty stomach, and thereby bring the results of the study as close as possible to the reference ones for this group of patients.

What factors can influence the results of laboratory tests? First of all, it should be noted the sensitivity of many laboratory tests to the time interval associated with the patient’s intake of food in general or individual products in particular, as well as the peculiarities of his eating behavior, for example, diet (meat or vegetarian), coffee and alcohol consumption. For example, high blood sugar may be related to a recent meal rather than diabetes. Eating shortly before the study will affect the results of lipid profile tests, insulin and C-peptide levels. In this regard, in order to obtain accurate results of the study, it is recommended to donate blood in the morning on an empty stomach, usually not less than 8 and not more than 14 hours after the last meal. On the eve of the study, food overload should be avoided.

High levels of liver enzymes may be due to recent or frequent alcohol use. Caffeine can cause an increase in the concentration of catecholamines and renin in plasma. Smoking sometimes causes a borderline increase in the level of some tumor markers.

Lab test results may be affected by vitamin and nutritional supplements and medications. In this case, the effect of drugs can be multidirectional. They can not only change the physiological processes in the body, but also chemically interfere (interact) with the analyzed analyte under conditions in vitro . An example of the effect of drugs on the physiological level is the increase in liver enzymes under the influence of hepatotoxic drugs. Drugs that affect plasma volume can cause changes in the concentration of proteins, urea nitrogen, iron and calcium. An example of another influence is non-specific binding reactions of certain drug metabolites with individual components of the reaction mixture, for example, polyclonal antibodies in immunoassays, as a result of which an erroneous result can be obtained. In this regard, a patient taking any medications should consult with a doctor about the advisability of conducting a laboratory study while taking medications or the possibility of stopping them before the study.

Among the factors affecting the results of laboratory tests is physical activity. Physical stress leads to a volumetric shift between the vascular bed and the intercellular space, loss of fluid with sweat and, as a result, to a change in the concentration of some analytes: hormones or enzymes. Therefore, visiting, for example, a gym on the eve of a laboratory test is undesirable. Heavy physical activity can cause an increase in the level of certain enzymes (ALT, AST, LDH, creatine kinase), a change in the level of various blood substrates (glucose, urea, etc.), and increase the excretion of protein in the urine. In addition, people who have been actively involved in sports for a long time, such as long-distance running or weightlifting, may have slightly increased levels of testosterone and luteinizing hormone (LH).

A general recommendation to prepare for the test is to rest (preferably sit) for 10 to 20 minutes after arriving at the laboratory before taking blood samples. This is also due to the fact that the results of some laboratory tests can be influenced by the body position of the subject at the time of its conduct, as well as the emotional state of the person before and during the study. So, for example, a change in body position from a lying position to a sitting or standing position causes vasoconstriction, and a change in position from a sitting to a lying position causes a shift of water and electrolytes in the tissue, leading to blood concentration. As a result, serum or plasma levels of total protein, albumin, lipids, iron and calcium change upward.

Emotional stress can cause significant increases in cortisol, ACTH and glucose levels. Among other things, stress is combined with an increase in the concentrations of albumin, fibrinogen, insulin, lactate and cholesterol. That is why it is so important, if possible, to exclude psycho-emotional stress on the eve of the study and try not to worry in the process of taking a biological sample.

Temporary changes in certain laboratory parameters may be caused by physiotherapy and instrumental examinations (eg, prostate biopsy before PSA testing). In such cases, it is recommended to postpone the laboratory examination for several days.

For a number of hormonal studies, it is important to take into account the phase of the menstrual cycle in women, and therefore you should check with your doctor in advance the optimal days for blood donation to determine the level of FSH, LH, inhibin B, prolactin, progesterone, estradiol and some other hormones.

Time of day during sampling is especially important when cortisol, thyroid stimulating hormone (TSH), and some other analytes are needed. At the same time, it should be borne in mind that the reference values ​​- the boundaries of the “normal” laboratory parameters, usually reflect the statistical data obtained under standard conditions when taking blood in the morning.

Thus, there are a number of reasons why the results of the analysis may fall outside the established range of reference values, even if the person is absolutely healthy. Therefore, if the patient is aware of any special circumstances that could affect the results of the studies, they should be reported to their doctor. Don’t expect him to figure them out on his own. After all, a result that does not correspond to the “norm” is not necessarily a sign of a disease, and therefore the doctor needs to understand its possible cause. It is possible that this is just the case when the result obtained falls into those very statistically significant 5%, in which the laboratory parameters of healthy people are outside the reference range. Sometimes some “abnormal” results can go back to normal on their own, especially if they were on the border of the reference values. In addition, there are not many diseases that can be diagnosed with just one single test.

The above examples show that in order to adequately evaluate the results of laboratory tests, as well as to make the right clinical decisions for the patient on the basis of them, a comprehensive approach is needed that takes into account all the variety of factors that can affect the accuracy and correctness of the data obtained . Clinical conclusions and decisions based on the results of laboratory analyzes will be correct only if the various preanalytical and analytical factors are sufficiently standardized and fully taken into account. It is very important that the patient be able to follow all the necessary recommendations for preparing for laboratory tests, and the attending physician, interpreting the data obtained, would take into account the possible impact on the result of the study of non-pathological factors that occurred, and also comprehensively evaluate the results, taking into account the clinical picture and data from other types research.

Laboratory diagnostics specialists, if necessary, are always ready to answer questions about the results obtained, provide additional special information and explanations or advise in complex cases.

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