Immunoblot analysis to determine the time of a primary CMV infection in pregnancy

<title>Abstract</title> <p>Aim To evaluate the utility of immunoblot analysis for determining the timing of maternal CMV infection in pregnancy. Methods Retrospective study including 151 pregnant women referred for suspected primary CMV infection at the University Hospital Tübingen between October 2023–June 2025. CMV-specific IgG, IgM and IgG avidity were measured and a CMV immunoblot assay was carried out. Associations between immunoblot band reactivity and CLIA IgG avidity as gold standard were analyzed by Firth penalized logistic regression and ordinal logistic regression. Results Increasing CLIA IgG avidity was associated with a decreasing probability of IgM p150 and IgG IE1, CM2 and p65 reactivity, and with a significantly increasing probability of IgG gB1, gB2 and avidity gB2 band positivity. Among cases with low CLIA IgG avidity (&lt; 15%; n = 56), absence of IgG avidity gB2 achieved the highest detection rate (92.9%) and absence of IgG gB1 the lowest false-positive rate (8.4%). Conclusion Immunoblot band patterns correlate systematically with CLIA IgG avidity and can help determine the timing of primary CMV infection in pregnancy. Absent IgG gB1 reactivity provides a specific marker for very recent infection, while absent IgG avidity gB2 offers high sensitivity.</p>