Evaluation of the automated vitek immunodiagnostic assay system (VIDAS) for the detection of measles (rubeola) IgG antibodies,

Abstract

The VIDAS MSG assay is a rapid, automated assay system for the detection of measles antibodies which has not yet been fully evaluated. To compare the VIDAS MSG assay with hemagglutination inhibition (HAI) and a commercial enzyme immunoassay (EIA) for the determination of measles immune status. Four hundred and seventy-seven serum samples collected from hospital employees for pre-employment screening were tested for measles antibodies using the VIDAS MSG assay and the results compared with those obtained by HAI and EIA. Intra-and inter-assay precision runs of the VIDAS instrument were evaluated using the positive standard provided by the manufacturer. The sensitivity of the VIDAS assay compared to HAI and EIA was 96.4% and 96.7%, respectively. The specificity of the VIDAS assay, when grouping equivocal with negative results was 77.6% and 100% compared to HAI and EIA respectively. The co-efficient of variation for both precision runs was less than 10%, indicating good reproducibility. The VIDAS MSG assay system is rapid and less labour intensive than HAI and manual EIA for the detection of measles antibody. The significance of equivocal results is not known, but may represent low, non-protective antibody levels. Testing of equivocal samples using another test may provide a definitive (positive or negative) result, but the degree of protection afforded by a positive result is not known. Alternatively, equivocals may be grouped with negatives for exposure or vaccination purposes. This may result in overuse of vaccine if the VIDAS MSG assay is used to determine immune status in screening programs such as pre-employment of hospital staff.