CLINICAL AND LABORATORY CHARACTERISTICS OF THE MODERN COURSE OF INFECTIOUS MONONUCLEOSIS AND THE ALGORITHM FOR ESTABLISHING THE DIAGNOSIS

Objective. To evaluate the diagnostic significance of clinical manifestations and laboratory markers in patients with typical and atypical infectious mononucleosis (IM) and to develop a diagnostic algorithm based on the obtained results. Patients and methods. A multicenter retrospective cohort study included 159 patients aged 16–65 years, divided into groups of typical IM (n=86), atypical IM (n=51), and acute respiratory viral infection (n=22). Clinical symptoms, ultrasound parameters of the liver and spleen, hemograms, biochemical indicators (alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and alkaline phosphatase (ALP)), as well as polymerase chain reaction (PCR) and serological test results were analyzed. Statistical processing was performed using Python. Results. Significant intergroup differences were identified. The highest diagnostic informativeness was demonstrated by virocytes (20 % in typical IM, 16 % in atypical IM, 1 % in controls), lymphocytosis, and increased ALT, AST, and LDH activity. ROC analysis confirmed the leading role of virocytes (AUC=1.0), as well as the significance of ALT (AUC=0.972), lymphocytes (AUC=0.970), and LDH (AUC=0.930). Based on threshold values of virocytes ≥3 %, lymphocytes ≥50 %, ALT ≥36 U/L, and LDH ≥392 U/L, a 12-point scale was developed with a sensitivity of 95.6 % and specificity of 100 %. Conclusions. Virocytes are the most specific indicator of IM, while elevated ALT and LDH activity serve as important auxiliary criteria, with LDH enabling differentiation between typical and atypical courses. The developed scale optimizes IM diagnosis.