DETECTION OF MEASLES IgM

Fewer physicians have experience in diagnosis of measles as the number of cases continues to decline. For this reason an Enzyme Linked Immunosorbent Assay (ELISA) was developed to detect measles virus specific IgM antibody (MIgMA). Anti-human μ chain is affixed to a solid phase to which a 1:100 dilution of serum is added. Only 0.005 ml of patient's serum is needed. Treatment of 3 MIgMA positive sera with dithiothreitol but not Staph protein A removed MIgMA. The values for 24 cord sera (0.030 ± 0.007), 60 adult sera (0.034 ± 0.011), and 47 sera from children prior to measles immunization (0.030 ± 0.015) were used to establish a seronegative range. Sera yielding reactions greater than 3 SD of the mean for the latter group were considered to be positive for the presence of MIgMA. MIgMA was not detected in sera with high titers of rheumatoid factor. Five unpaired and the first of 14 of 17 paired sera obtained from patients with measles were positive for MIgMA. The 3 convalescent samples from patients having MIgMA negative initial sera, also were positive. MIgMA was detected as early as 1 day and as late as 41 days following onset of illness. No MIgMA could be detected in 47 vaccinees tested 2-1/2 months or more after measles vaccination. Neither recent immunization nor the presence of rheumatoid factor produce reactions which are likely to obfuscate the interpretation of this very sensitive test which, in most cases, can confirm the clinical diagnosis of measles on a single serum specimen obtained soon after onset of rash.