Clin Vaccine Immunol. 2014 Jan 29. [Epub ahead of print]
Performance of the BioPlex(R) 2200 flow immunoassay (Bio-Rad) in critical cases of serodiagnosis of toxoplasmosis
The BioPlex® 2200 automated analyzer (Bio-Rad Laboratories, Hercules, CA) is a recent multiplex analyzer allowing the detection of anti-Toxoplasma, rubella and cytomegalovirus antibodies in the same assay. The aim of this study was to compare this new technology (using BioPlex® 2200 ToRC IgG/IgM kit) in critical cases of serodiagnosis of toxoplasmosis (acute, chronic, congenital infections and cases with discrepant results) to our routine practice: Platelia IgG/IgM ELISA test (Bio-Rad Laboratories) and Toxo-Screen Direct Agglutination assay (bioMérieux, Lyon, France). Overall, most cases of false positive/negative results obtained with Platelia IgG or Toxo-Screen were corrected by BioPlex® 2200 ToRC IgG (87.5%). Furthermore, the analysis of 35 sequences of sera showed a trend to a more rapid decrease of IgM titers by BioPlex® 2200 than by Platelia. These results for IgM detection can be explained by a weaker detection of residual IgM. Indeed, among 23 sera from probable past infection with long lasting IgM (Platelia M+ and IgG avidity index ≥ 0.5), the BioPlex® 2200 Toxoplasma IgM assay was positive in only 11 sera. In our panel of critical cases comprised of 156 sera and 6 cord bloods from 103 patients with acute, chronic or congenital infection, the BioPlex® 2200 IgG assay is a sensitive (97.8%) and specific (91.3%) method for IgG detection. The high specificity (97.4%) of IgM detection combined with the shorter kinetics of IgM titers may considerably reduce the number of residual IgM detections, thus yielding more precise diagnosis of acute infections.
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