FIELD: medicine, pediatrics. SUBSTANCE: one should determine health level at every critical period (age of 2-4, 6-8, 13-16) of postnatal ontogenesis by three stages - primary studying at detecting the initial health level, repeated survey and the final studying. Diagnostic coefficients of informative factors and criteria including: more severe genealogical, social-medium and biological anamneses, level of physical development, level of resistance, peculiarities of autonomic nervous regulation, type of pathological states. And diagnostic coefficients of informative biochemical values of condensate of expired air: level of total lipids, determination of calcium, potassium, lactate and acylhydroperoxides in accordance with Table 1. According to the data one should calculate diagnostic coefficient of critical period with the help of formula calculating trapezoidal area. At its value being above 80 c.u. in children aged 2-4, above 75 c.u. in children aged 7-8 and above 38 c.u in children aged 13-16 one should conclude upon the flow of critical period to be pathological. EFFECT: more simplified method and higher accuracy of diagnostics. 2 ex, 1 tbl
