False-positive IgM antibody tests for cytomegalovirus in patients with acute Epstein-Barr virus infection

The diagnosis of acute cytomegalovirus (CMV) infection is frequently based on a positive IgM result. False-positive reactions due to interfering infec tions may exist. Between August 1998 and May 1999, 62 patients were found t o be IgM positive and IgG negative with the Axsym assay (Abbott, Ger many). Serological testing for Epstein-Barr virus (EBV) was performed in these pa tients to detect any cross-reactivity due to acute mononucleosis. Additiona lly, the results of the CMV Axsym was evaluated in 40 patients with acute E BV infection. The results suggest that the CMV-IgM Axsym assay shows a lack of specificity due to acute EBV infection. Precautions must be taken when CMV-IgM Axsym results are interpreted. It seems necessary to confirm equivo cal results with another technique and to take into account other clinical and biological observations.