EVALUATION OF THE AUTOMATED VITEK IMMUNODIAGNOSTIC ASSAY SYSTEM (VIDAS) FOR THE DETECTION OF MEASLES (RUBEOLA) IGG ANTIBODIES

Background: The VIDAS MSG assay is a rapid, automated assay system for the detection of measles antibodies which has not yet been fully eval uated. Objectives: To compare the VIDAS MSG assay with hemagglutinatio n inhibition (HAI) and a commercial enzyme immunoassay (EIA) for the d etermination of measles immune status. Study design: Four hundred and seventy-seven serum samples collected from hospital employees for pre- employment screening were tested for measles antibodies using the VIDA S MSG assay and the results compared with those obtained by HAI and EI A. Intra-and inter-assay precision runs of the VIDAS instrument were e valuated using the positive standard provided by the manufacturer. Res ults: The sensitivity of the VIDAS assay compared to HAI and EIA was 9 6.4% 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 pr ecision runs was less than 10%, indicating good reproducibility. Concl usions: The VIDAS MSG assay system is rapid and less labour intensive than HAI and manual EIA for the detection of measles antibody. The sig nificance of equivocal results is not known, but may represent low, no n-protective antibody levels. Testing of equivocal samples using anoth er test may provide a definitive (positive or negative) result, but th e degree of protection afforded by a positive result is not known. Alt ernatively, equivocals may be grouped with negatives for exposure or v accination purposes. This may result in overuse of vaccine if the VIDA S MSG assay is used to determine immune status in screening programs s uch as pre-employment of hospital staff.