FIELD: immunology; prognosis of development of nonspecific inflammatory diseases. SUBSTANCE: patient's blood sample is taken, followed by preparing blood serum in order to determine content of G, M and A class immunoglobulins. Simultaneously, patient's blood is subjected to analysis to determine absolute B-lymphocyte number. Resistance index is calculated using the following formula: RI = (M + G + AB) x 100, where M is M class immunoglobulin content, gl; G is class immunoglobulin content, g/l; A is A class immunoglobunin content, g/l; B is absolute B-lymphocyte number, cl/mcl. If RI values are more than 5.78, resistance of given organism is considered to be high, at 3.04<RI<5.78 it is weakened, and at RI below 3.04 it is low. EFFECT: higher diagnostic accuracy. 1 tbl
