DIAGNOSIS OF MEASLES WITH AN IGM CAPTURE EIA - THE OPTIMAL TIMING OF SPECIMEN COLLECTION AFTER RASH ONSET

The optimal timing for collection of a single serum specimen to diagno se measles by using a monoclonal antibody-capture EIA was evaluated. R esults of testing paired serum samples from 166 measles cases with at least 1 IgM-positive specimen were analyzed. Among persons whose secon d samples were IgM-positive, the seropositivity rate for first samples was 77% when collected within 72 h and 100% when collected 4-11 days after rash onset, Among unvaccinated persons whose first samples were IgM-positive, the rate for IgM positivity of second specimens declined from 100% at 4 days to 94% at 4 weeks after rash onset, then declined further to 63% at 5 weeks, Some previously vaccinated persons became IgM-negative during the third week after rash onset, In general, a sin gle serum specimen collected between 72 h and 4 weeks after rash onset can be used to diagnose most cases of measles with an IgM capture EIA .