Parvovirus B19 infection in pregnancy: quantitative viral DNA analysis using a kinetic fluorescence detection system (TaqMan PCR).

Human parvovirus B19 infections are common in the general population, and infection during pregnancy may cause hydrops fetalis and fetal death. To initiate adequate treatment, accurate laboratory diagnosis is essential. The most sensitive tests are nested PCR systems, but these assays provide semiquantitative results at best. A parvovirus B19 DNA assay was developed based on the real time TaqMan PCR. This method was calibrated on the basis of serial plasmid dilutions and tested with an international parvovirus B19 standard. The assay was capable of quantifying parvovirus B19 DNA from one to about 5 x 10(7) genome equivalents per reaction (corresponding to 100 to 5 x 10(9) genome equivalents per ml serum). Samples from 51 pregnant women with suspected acute parvovirus B19 infection were tested, and positive PCR results were obtained in at least one of the materials investigated in 41 cases. The median viral DNA load in maternal blood samples was 1.3 x 10(4) copies/ml (range 7.2 x 10(2)-2.6 x 10(7)). Maternal virus DNA concentration was not associated with the presence of maternal symptoms and/or fetal complications. As the stage of infection was not known in the majority of cases, our data do not exclude an association between peak levels of parvovirus B19 DNA and the development of complications. Maternal sera and corresponding fetal material were available for concurrent testing from 15 DNA-positive cases: in most fetal samples, viral DNA concentrations were several orders of magnitude higher (up to 2.1 x 10(12) copies/ml) compared to the corresponding maternal blood samples.