Evaluation of the Abbott AxSYM cytomegalovirus (CMV) immunoglobulin M (IgM) assay in conjunction with other CMV IgM tests and a CMV IgG avidity assay

The measurement of the avidity of cytomegalovirus (CMV) immunoglobulin G (I gG ) antibodies has been shown by several investigators to be useful in ide ntifying and excluding primary CMV infections in pregnant women. In this wo rk we examined the diagnostic utility of reflex testing of CMV IgM-positive specimens from pregnant women by using a CMV Ige avidity assay. The utilit y of this approach was directly dependent on the sensitivity of the CMV igM assay employed during the initial screen. The higher initial reactivity ra te of the AxSYM Chn IgM assay was necessary in order to detect CMV IgM in s pecimens containing low-avidity Chn IgG antibodies, indicative of a primary CIMV infection, which other cMv IgM assays (Behring, Vidas, Captia, and Eu rogenetics) fail to detect in some cases. The use of the AxSYM cMv IgM assa y, followed by an avidity test, should result in more accurate diagnosis of CMV infection in pregnant women.