Introduction. According to the classical definition, quality in laboratory practice is "a correctly and timely prescribed test for a patient in need." In other words, when prescribing a laboratory study, the attending physician proceeds from suspicions of the presence of a certain disease, based on medical history, physical and instrumental examination methods. Obviously, there is an unambiguous relationship between the age of manifestation of the disease and the age of patients who need to conduct a study of the concentration of specific analytes. Purpose of the study: to study the age characteristics of patients assigned to immunochemical studies. Materials and methods. A single-center retrospective study was conducted on the data of the laboratory information system on services performed in the immunological research department of the clinical diagnostic laboratory of St. Petersburg State Budgetary Healthcare Institution "GMPB No. 2" from 01.01.2022 to 31.12.2024. Correlation analysis was carried out using the Spearman rank correlation coefficient. Statistical processing was carried out using the SPSS Statistics 20.0 application package. Results. A correlation analysis between the median age of prescribing tests for 2022 and 2023 showed a strong relationship with Spearman's rank correlation coefficient r 0.967 at the significance level p