Low-level positive results in the Liaison CMV IgG II assay may misclassify pregnant woman as immune

Abstract

The aim of this study is to report on the specificity in the low-positive range of the Liaison CMV IgG II assay for determination of cytomegalovirus immune status in pregnancy. Sera with test results between 12.0 and 40.0 U/mL were retested with the Enzygnost Anti-CMV/IgG assay. Enzygnost-negative samples were analyzed by the Serion ELISA classic Cytomegalovirus IgG assay and, if positive or equivocal, also with the Mikrogen recomLine CMV IgG assay. A total of 12,117 sera were tested with the Liaison assay. Sixty sera were equivocal (12.0–13.9 U/mL), and 400 of 4295 positive sera were low-positive (14.0–40.0 U/mL). Based on consensus, at least 14% of the low-positives and 1.3% of all Liaison-positives can be considered as misclassified. The proportion of misclassified sera increased with lower Liaison IgG results. We suggest that the range for equivocal results in the Liaison assay should be revised.