Identification of past and recent parvovirus B19 infection in immunocompetent individuals by quantitative PCR and enzyme immunoassays: a dual-laboratory study.

Parvovirus B19 (B19V) is a member of the family Parvoviridae, genus Erythrovirus. B19V-specific IgG and IgM react differently against conformational and linear epitopes of VP1 and VP2 antigens, leading to the development of IgG avidity and epitope type specificity (ETS) enzyme immunoassays (EIAs) for distinguishing past from recent infection. Additionally, B19V viral load determination (by quantitative PCR [qPCR]) is increasingly used in the staging of B19V infection. In this study, the utility of these methods is compared. A panel of 78 sera was jointly tested by the Virus Reference Department (VRD), London, United Kingdom, and the Haartman Institute (HI), Helsinki, Finland, using a number of EIAs, e.g., B19V-specific IgG and IgM, IgG avidity, and ETS EIAs. At VRD, the sera were also tested by a B19V viral load PCR (qPCR). By consensus analysis, 43 (55.1%) sera represented past infection, 28 (35.9%) sera represented recent infection, and 7 (9.0%) sera were indeterminate. Both VRD B19V qPCR and HI B19V VP2 IgM EIA gave the highest agreement with consensus interpretation for past or recent infection, with an overall agreement of 99% (95% confidence interval [CI], 92 to 100) and positive predictive value (PPV) of 100% (95% CI, 87 to 100). Nine sera designated as representing past infection by consensus analysis were B19V IgM positive by a commercial VRD B19V IgM EIA and B19V IgM negative by a new HI in-house B19V VP2 IgM EIA. A new VRD B19V IgG avidity EIA showed good (>95%) agreement (excluding equivocal results) with consensus interpretations for past or recent infection. Correct discrimination of past from recent B19V infection was achieved through application of qPCR or by appropriate selection of EIAs.