Sensitivity and specificity of mu-capture ELISA for detection of enterovirus IgM

The sensitivity and specificity of an in-house mu-capture enzyme linked immunosorbent assay (ELISA) for enterovirus IgM in routine use was determined by analysing the results of 77 serum samples from 55 enterovirus culture-positive patients with aseptic meningitis and single serum samples from 140 patients with other infections. In addition, sera from 10 laboratory staff pre- and post-polio virus vaccination and 20 rheumatoid factor positive sera were rested for specificity. On testing the first serum specimen received, only 21 of 55 patients (35%) with aseptic meningitis yielded a positive result, rising to 33 of 55 (60%) on testing a second sample, where available. Out of 14 patients from whom multiple serum samples were tested and negative results obtained with the first serum, 12 were positive with the second sample (86%). Only patients with acute hepatitis A produced a significant number of false positives by the enterovirus ELISA (12 out of 20), but the reverse was not true: patients with enterovirus IgM did not produce false positive results in tests for hepatitis A IgM. Excluding samples positive for hepatitis A IgM, the number of non-enterovirus infections correctly reported as negative was 118 out of 120 - a specificity of 98%. This test is probably the most useful serological test available at present for diagnosing recent enterovirus infection, although the limited sensitivity needs to be borne in mind.