Reference values - what is it? What does "reference value" mean?

When carrying out any diagnostic measures, the results of the studies are considered in a comprehensive manner. This takes into account all indicators: the general condition of the patient, the nature of the pathology, symptoms.

Quantitative and qualitative research

The results of a number of laboratory tests are given to the patient in the form of "positive" or "negative". This form is considered a qualitative characteristic. An example is the analysis of antibodies to a particular infection. A positive result indicates the presence of these antibodies in the material.

What does "reference value" mean?

In the quantitative type of research, the results are given in the form of numbers. In this case, there is a range of norms, as well as average indicators. The reference value in the analyzes is the term of medicine used to evaluate the results in laboratory studies. It is defined as the average value of a certain indicator. These data were obtained by examining a healthy part of the population. To begin with, you can consider some of the reference values of thyroid hormones. For example, for free T3, the values 1.2-2.8 mMе / l are normal, and for the thyroxine (general) - 60.0-160.0 nmol / l. That's how the indicator of TSH analysis may look : the reference values are 0.5-5.0 μIU / ml, and the result is 2.0. As can be seen from the last example, the figure obtained in the study is in the normal range.

How are normal boundaries defined?

The only way, as already mentioned above, is to examine healthy people. The first stage is a sample of the population. For example, healthy women are invited, ages from twenty to thirty. Most of them are assigned clinical studies. The results are reduced to the average digits, calculating the range in which the reference values are located. Deviation from normal indicators (one way or the other) is allowed for two standard units.

Why do different laboratories produce different results?

Depending on the test method used and the measuring instrument, certain reference values are given out. In different laboratories different equipment can be used, this or that unit of calculation can be used. In accordance with this set and ranges of indicators.

When receiving the result, the letterhead should contain the numbers and units of measurement used in the particular laboratory. Thus, in medicine, for example, there are no single reference values for the blood test. The specialist in reviewing the results should refer to the figures used by the institution in which the patient was examined. The difference can be seen by examining, for example, certain reference values of the biochemical blood test. Thus, the range of indices for ethylidene when tested by the G7PNP method is 28-100 U / l, and the CNPG3 method is 22-80 U / l.

Why indicators can go beyond the limits of norms?

The reference value in the analyzes is statistical data, but not the biological law. In some cases, deviation from the limits of established ranges may be observed even in healthy people. How can this be caused? Among the many causes of abnormalities, physiological characteristics of the organism are of particular importance. If a specialist recommends one laboratory test several times, then there is a certain probability that a deviation from the normal limits will appear in the results. In accordance with biological causes, indicators can change daily. To compare the results, the doctor prescribes the tests again. As a rule, diagnostic conclusions are made not in accordance with individual indicators, but in assessing the dynamics of changes. In healthy people, data may not fall within the generally accepted ranges. In this case, for the people themselves, the results will be considered the norm. Such cases usually involve minor deviations. Nevertheless, indicators that do not fall into reference values may indicate abnormalities in the body that require further diagnostic measures. The specialist, evaluating the results of the studies, takes into account the general condition of the patient, the clinical picture, studies the medical history and other factors. As a result, the doctor determines what the deviation from normal figures indicates.

What factors can affect the results of research?

The laboratory can give the patient results in accordance with his gender and age. For example, reference values of creatinine (in the study of serum) in men under 50 years of age - 74-110 μmol / l, after 50 - 70-127 μmol / l. In women, the indices are established regardless of age and are 60-100 μmol / l. The reference values of hCG for the fair sex depend on whether the patient is pregnant or not. The results of the research can be affected by the treatment received, the peculiarities of the regime of the day and nutrition. An important factor are bad habits: smoking, alcohol abuse or coffee. Even the posture of the patient in the process of putting the material can affect the performance. For example, the content of calcium and albumin may increase when the patient's position changes from horizontal to vertical. To obtain a more accurate result before the examination, a specialist can recommend to exclude physical activity, stressful situations, to give up smoking and alcohol, taking medicines and vitamins.

Influence of physical loads on results

It is not recommended to visit the gym the day before. Physical loads affect the enzymatic activity of creatine phosphokinase, lactate dehydrogenase, aspartate aminotransferase. Athletes who have been involved in heavy or athletics for many years can increase the level of luteinizing hormone, platelets and testosterone. Given all these factors, you must follow certain rules before passing the tests. When preparing for a particular study, the doctor, as a rule, gives special recommendations. If the patient follows the prescription of a specialist, then he has a much better chance of getting accurate and correct results.

Common misconceptions

There are several erroneous opinions about the reference values and, in fact, the research results. Many believe that deviations from the norm necessarily indicate a violation in the body. However, this is not always the case. Results that go beyond the generally accepted ranges indicate the need for further examinations or re-analysis. It is likely that the result does not indicate a violation, but falls in 5% of cases in which deviations are observed in healthy people. In any case, the doctor will take the necessary measures to accurately assess the situation. As already mentioned above, there are many factors that can influence the outcome. For example, high blood sugar can indicate not on diabetes, but on the error in nutrition. The level of lipids increases in the case of delivery of the analysis not on an empty stomach. The increase in the content of hepatic enzymes may be due to the use of alcohol on the eve of the study, and not with cirrhosis. Among other things, the results are influenced by medications taken. Today, pharmacological enterprises produce a huge number of drugs. Laboratories sometimes simply do not have time to assess their effect on blood or other test material. In a number of cases, the values can come to normal independently, if they were on the boundary of the reference values.

Should I worry if the results of the research are within the limits of the norm?

In general, such indicators are undoubtedly a good sign and indicate the absence of any violations in the body. However, according to many experts, a certain set of studies does not guarantee the complete absence of health problems. With statistical processing of reference ranges, there is always a partial coincidence of the results of people with pathologies and healthy ones. In other words, the latter can deviate from the norm in the absence of disturbances in the body's activity. Similarly, in people with pathologies, the test results can be within the normal range. To refine the indicators, as a rule, repeated studies are assigned after a certain period. When assessing the dynamics of changes, the specialist either notes the absence of violations or suspects any pathology. In the second case, additional tests are used to clarify the diagnosis.