Data are shown in Table ?Table1.1. IgMs against heterologous viral agents. The presence of IgMs against Epstein-Barr virus (EBV), cytomegalovirus (CMV), human herpesvirus 6, measles virus, and rubella virus has been reported to occur in sera from patients with acute human parvovirus B19 infection (3, 5-7). IgM antibodies against unrelated viruses appearing in the setting of acute parvovirus B19 infection may be either cross-reactive antibodies or truly virus-specific antibodies secreted as a result of heterologous virus reactivation driven either directly or indirectly by parvovirus B19 infection. Alternatively, false-positive results in viral IgM assays may occur as a result of spurious binding of nonspecific serum antibodies to the solid phase. In this context, it has been recently reported (1) that an exceedingly high percentage of sera drawn from patients with either a conclusive or a presumptive diagnosis of acute parvovirus B19 infection gave a false-positive result in several IgM immunoassays (EBV, CMV, herpes simplex virus, and sensu lato) from DiaSorin (Saluggia, Italy) performed on the Liaison platform. The false-positive reactivities were apparently due to nonspecific binding of IgMs to the A66 antigen-coated beads used in the assay (2) and were found to be partially eliminated (although sera remained positive) by adding polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA) to the dilution buffer. The diagnostic relevance of the above findings prompted us to evaluate the performance of the DiaSorin EBV and HSV IgM assays with sera from acutely parvovirus B19-infected individuals in our establishing. Sixty-five sera from 65 individuals (45 females and 20 males, aged 4 to 70 years, median age of 15 years) having a presumptive medical and/or biological analysis of acute parvovirus B19 illness sent to our laboratory from January 2005 to January 2009 were retrieved for analysis. These sera had been tested in the parvovirus B19 enzyme immunoassay (EIA) from Biotrin International (Dublin, Ireland) and found to be IgG and IgM positive (= 53) or IgG bad Mouse monoclonal to CD63(PE) and IgM positive (= 12). In the Biotrin assay, antibodies against a baculovirus-expressed VP2 conformational protein are recognized. The B19-specific IgM assay is definitely a mu capture EIA, while the IgG assay is an antigen capture EIA. This immunoassay offers 89.1% level of sensitivity and 99.4% specificity for IgM detection (4). Clinical data were available for 41 individuals. These individuals displayed fever and one or more of the following medical or biological indicators compatible with acute parvovirus B19 illness: exanthema, arthralgia, and mono- or pancytopenia. To confirm the acute nature of parvovirus B19 illness, IgG avidity checks were performed. In brief, parvovirus B19 IgG avidity was identified with the Biotrin assay. The first step of the assay was altered to include two washes (5 min each) having a washing buffer comprising urea (4 M). The AI value (as a percentage) was determined as follows: (absorbance of parvovirus B19 IgGs in the presence of urea/absorbance of parvovirus B19 IgG in the absence of urea) 100. AI ideals of 25% are seen early after illness, and AI ideals of 80% are observed in past infections (8). In our encounter, AI ideals of 40% should be considered indicative of a recent illness when using urea at 4 M in the washing buffer (unpublished observation). IgG AI ideals were identified for 20 of the 53 parvovirus B19 IgG-positive sera of which a sufficient sample volume was available A66 for analysis. All A66 20 sera offered AI ideals of 40% (median, 32%; range, 6.6 to 39.42%), as a result confirming the acute nature of the parvovirus B19 illness in these individuals. In 8 of the 12 individuals with an isolated IgM reactivity profile in the acute-phase serum specimen, acute parvovirus B19 illness was confirmed by demonstration of seroconversion in convalescent-phase sera. No follow-up samples were available for the remaining four individuals. Thirty-four of these sera had been tested for viral capsid antigen IgM antibodies (Captia VCA IgM; Trinity-Biotech, Bray, Ireland) as requested and found to be bad. Fifty-five sera were tested for HSV IgMs (Herpes simplex 1 + 2 IgM test; Vircell, Granada, Spain). Forty-four sera experienced a negative result, seven displayed a positive result, and four experienced an indeterminate result. The sera were tested in the EBV IgM (= 65) and HSV IgM (= 55) assays from DiaSorin within the Liaison platform. Interpretation of results was done according to the instructions of the manufacturer. Data are demonstrated in Table ?Table1.1. None of the sera tested positive in the EBV.