COMPARATIVE ANALYSIS OF DIFFERENT MANUFACTURERS KITS FOR DETERMINING CLASS G ANTIBODIES TO MEASLES VIRUS

Relevance. The implementation of the WHO-declared goal of measles elimination requires a well-established system of epidemiological surveillance and monitoring of population immunity levels, which must be at least 95%. Therefore, high accuracy of serological tests for identifying susceptible individuals is critically important, particularly in the range of low values approaching the "gray zone." Widely used ELISA test systems from various manufacturers, which have replaced the WHO-recommended Enzygnost (Siemens) test systems, exhibit variable sensitivity, potentially leading to underestimation of measles-susceptible individuals in population immunity studies.

Objective. To compare the results of measles virus IgG antibody detection by ELISA using kits from four different manufacturers.

Materials and Methods. Blood serum samples from 88 measles patients were tested. Four kits intended for quantitative and qualitative determination of IgG antibodies to the measles virus were used: VectoMeasles-IgG (Vector-Best), ELISA-Measles-IgG (Ecolab), Rapid-Measles-IgG-ELISA (Rapid Bio), and Anti-Measles Virus ELISA (IgG) (Euroimmun). The test systems differed in the measles virus antigens employed and in the cut-off thresholds used to classify results as positive or negative. Both qualitative and quantitative analyses of the results were performed, with antibody concentrations calculated in IU/mL. Data processing was carried out using nonparametric statistics and Pearson correlation analysis.

Results. Among the four test systems, the Rapid kit yielded the highest number of indeterminate results. Ecolab produced the highest number of positive results (64 samples, 72.7%), while Euroimmun produced the lowest number of positive sera (46 samples, 52.3%). In the high-value range, all kits identified all sera with high IgG levels. Substantial differences were observed in the low and equivocal value ranges. The best agreement was demonstrated by the Vector-Best/Euroimmun and Rapid/Euroimmun pairs (90% concordance). Vector-Best/Rapid showed 83% concordance. Ecolab/Vector-Best yielded 77%, Ecolab/Euroimmun 76%, and Ecolab/Rapid 70%.

Conclusion. High comparability of results obtained using different test systems is essential for establishing an accurate picture of population immunity. The observed discrepancies are largely attributable to differing cut-off thresholds for result classification. The greatest disagreements occur precisely in the range of low and equivocal values. When a result falls within this problematic zone, retesting the sample using an alternative test system is advisable.