Value of immunoglobulin G avidity for primary cytomegalovirus diagnosis in pregnant women compared to nested polymerase chain reaction

Primary human cytomegalovirus (HCMV) infection in pregnancy especially in the first term carries high risks to foetus. Diagnosis depends mainly on laboratory tools as clinical diagnosis is non specific. The aim of the present study was to detect recent infection with HCMV in cohort pregnant Egyptian women in the first trimester by serological detection of specific IgM, IgG and IgG avidity test compared to nested PCR method. This study was performed on consecutive pregnant women. Blood samples were obtained and sera were separated from 120 pregnant women in their first trimester of pregnancy and were screened for anti-CMV IgG, IgM and IgG avidity by ELISA and for HCMV-DNA by PCR. Positive IgG for HCMV was 62.5% and positive IgM was 15%. IgG avidity results showed that low, intermediate and high avidity represented 33.3%, 16.7% and 50%, respectively of IgM positive patients and 42.1%, 38.6% and 19.3%, respectively of IgM negative patients. Detection of HCMV DNA by PCR was positive in one of 24 IgM negative/low IgG avidity, in three of 22 IgM negative/intermediate IgG avidity and in all IgM positive/low IgG avidity patients. Confirmatory testing for primary infection with the combined use of IgG avidity with IgM antibody test in pregnant women during the first trimester is an accurate screening tool. The use of PCR as a diagnostic method can be applied to pregnant women with IgM antibodies and low IgG avidity results or in presence of isolated low or intermediate avidity IgG.