Evaluation of 4 commercial test kits for parvovirus B19-specific IgM.

Four commercial test kits for parvovirus B19 IgM were evaluated by testing 491 sera assembled into 7 panels. The serum panels were designed to assess sensitivity and specificity of the commercial assays and to reflect the various clinical settings in which acute B19 infection forms part of the differential diagnosis. A mu-capture radioimmunoassay (MACRIA) was used as the reference test. With respect to MACRIA, the commercial B19 IgM assays showed an overall sensitivity of 70.1-84.1% and specificity of 92.2 to 97.4%. Assay performance varied in different clinical situations. In sera from adults with acute B19 arthropathy, all 4 assays were 100% sensitive, but in children with fifth disease, the sensitivity ranged from 44.1 to 88.6%. The sensitivity of all 4 assays was also low when testing samples collected more than 6 weeks after onset of symptoms and in women with B19-associated embryopathy. Specificity was greater than 97% in healthy blood donors, but varied from 70.9 to 83.3% in patients acutely infected with other viruses, including rubella. Although the IgM test kits here evaluated may be usefully introduced for B19 diagnosis in certain settings, knowledge of their limitations will be important when results have been interpreted.