Problems with serum IgM as a screening test for congenital infection

The purpose of this study was to determine the usefulness of the total serum IgM level as a screening test for congenital infection in asymptomatic or mildly symptomatic infants. A retrospective medical record review was performed on 168 infants in whom the serum IgM was measured as a screen for congenital infection. The indications for testing, the yield of testing, and the adequacy of follow-up of abnormal values were examined. Only one infant was diagnosed with a congenital infection which was not specifically suspected prior to screening; this was a case of congenital cytomegalovirus (CMV). Inappropriate screening was frequently performed in infants in whom indications for specific evaluation were present. Appropriate follow-up testing was performed in only 30% (seven of 23) of the infants with elevated serum IgM who received their pediatric care at our institution. Because of the low yield (< 1%) and lack of follow-up shown in this study, as well as poor sensitivity, serum IgM was not a useful screening test for congenital infection in our institution.