Ability of three IgG-avidity assays to exclude recent cytomegalovirus infection

At present, the measurement of IgG avidity appears to be the best method fo r differentiating primary from nonprimary cytomegalovirus (CMV) infection. This study compared the performances of three denaturation assays for the m easurement of CMV IgG avidity: an in-house method and the commercially avai lable assays Enzygnost (Dade-Behring, Germany) and Vidas (bioMerieux, Franc e). The ability of these assays to exclude or to detect a recent CMV infect ion were calculated according to the results obtained in two control groups of pregnant women: 49 who had seroconverted and 80 with past infections. A ll three assays demonstrated a good ability to detect a recent infection (9 8-100%). The Dade-Behring test, in its present form, appears to be ineffect ive in excluding a recent CMV infection (exclusion ability: 30%), while the in-house method (exclusion ability: 96%) and the bioMerieux method (exclus ion ability: 82%) performed better. The practical use of the in-house and t he bioMerieux assays was evaluated in 80 women with CMV-specific IgG and a positive IgM result but without documented seroconversion. At the recommend ed diagnostic thresholds, the concordance between these two tests was 70%. Larger studies will allow more precise determination of the capacities of b oth assays and specification of the diagnostic thresholds or grey areas to be used.