Consistent performance of cytomegalovirus IgG assays across platforms contrasts with marked IgM variability,...

CMV serology is vital for screening at-risk populations. While IgG assays show high accuracy, IgM interpretation is challenged by assay variability and the lack of a gold standard, especially in high-prevalence settings. This study evaluates four platforms to refine diagnostic classification. Performance of Mindray (CLIA), Abbott (CMIA), Roche (ECLIA), and NovaLisa (ELISA) was assessed using 319 (IgG) and 237 (IgM) samples against a "composite silver standard" (concordance in ≥ 3 assays). IgG avidity adjudicated discordant IgM results. CMV IgG seropositivity was consistent: Mindray (71.8%), Abbott (71.5%), NovaLisa (69.0%), and Roche (67.1%), aligning with the silver standard (69.6%). IgG assays showed almost perfect agreement (κ = 0.91-0.95), with sensitivities 96.9-99.1% and specificities 90.5-98.9%. Conversely, IgM seropositivity varied significantly: Abbott (18.6%) and NovaLisa (18.1%) were significantly higher than the silver standard (5.5%; p < 0.01), while Mindray (8.9%) and Roche (9.7%) aligned closer. IgM agreement was only fair-to-moderate (κ = 0.34-0.58). Avidity confirmed most isolated IgM-positive results did not reflect recent infection. CMV IgG detection is robust across platforms and suitable for clinical use. However, marked IgM discordance limits its standalone utility, supporting an IgG-based diagnostic strategy supplemented by avidity testing in high-prevalence populations.