Economic impact of switching rubella IgG methodologies to the prenatal public health program in Alberta

BackgroundDespite widespread use of a universal rubella standard, variability in rubella antibody titre can be observed between assays, particularly at the low end of the linear range.ObjectivesHere, we investigate the impact of a methodology change for rubella IgG from the Abbott AXSYM to the Abbott Architect in a comprehensive prenatal screening program in the Canadian province of Alberta.Study design51,815 specimens (21,399 tested by AxSYM and 30,416 tested by Architect) submitted for routine prenatal screening between January 2006 and December 2012 from women who lived in Alberta after the universal childhood immunization programme for rubella was implemented, and whose immunization records were available, were included in the study.ResultsPrenatal samples tested by AxSYM for rubella IgG were approximately 30% higher than those reported by Architect. Among individuals who had tests across multiple pregnancies, the change in test platform led to an additional 7% of women who initially tested positive, becoming non-positive (i.e. negative or indeterminate) in their subsequent tests. The tendency of the Architect IgG assay to report lower quantitative values was demonstrated across all birth cohorts and vaccination status, and resulted in an additional 2800 women requiring vaccination between 2010 and 2012 with an estimated cost of $38,500.ConclusionThe change in rubella IgG screening assay resulted in a significant increase in the number of women who required post partum vaccination and Public Health follow-up.