The reference value is applied to the following laboratory studies to assess the result of the analysis require certain information about the object of study. The "normal" result must fall within the range of reference values defined for the relevant part of the population, selected according to sex, age or any other indicator.

The studied group of healthy people is not accidental - it is determined by the initial sampling of the target group, which is designed for a specific type of research. Then a certain (sufficiently large) number of people in this group, studies on the definition of this indicator. For a received set of values determine the mean and calculate the range of reference values, which equals plus or minus two calculated standard deviations from the average.

The terminology "reference values" of a particular indicator more properly reflects the nature of the research than the "normal value" because this term shows the relative importance of the obtained results and their applicability only in a specific group of the population. The evaluation of the results of the study are different in gender, age characteristics of groups of people noticeable significant differences between the reference values of different selected subgroups. So, for example, a General and biochemical blood parameters in values are the reference for the total group of women 20-30 years, are no longer the reference for pregnant women, the body undergoing significant changes.

The reference values are not absolute for a given indicator, even in a selected group of people. In the world there are a small number of indicators of laboratory tests, for which the standard reference values. For the majority of indicators each laboratory establishes its own reference ranges in connection with the difference in equipment used, methods of research, the use of different private or international, depending on the methods used, the test-systems of units.