Evaluating the impact of reagent lot changes and environmental factors on quality control consistency in a measles IgM enzyme-linked immunosorbent assay

Abstract

Accurate serological testing relies on robust quality control (QC) procedures and the identification of factors influencing assay reliability. This retrospective study evaluated the impact of ambient laboratory conditions and reagent lot variability on the performance of the Euroimmun Anti-Measles Virus NP IgM ELISA, using data from 215 valid assay runs conducted between January 2023 and December 2024. QC metrics—Positive Control, Negative Control (NC), and Internal Quality Control (IQC) ratios—were analyzed across nine reagent kit lots. The IQC material, prepared and validated by the national serology reference laboratory, was used consistently to monitor longitudinal performance. Ambient temperature (20.0–25.0 °C) and humidity (21–84%) showed no significant linear correlation with QC ratios (p > 0.05). However, statistically significant variation in QC values was observed across reagent lots, especially for NC and IQC. NC failures (~ 7.7%) were dispersed and not linked to environmental extremes, suggesting possible procedural variation. In select instances, the IQC flagged deviations not captured by kit-supplied controls, underscoring its added value. These findings highlight reagent lot variability as the primary contributor to QC variation and reinforce the need for lot-specific validation, consistent monitoring, and integration of independent IQC materials as part of a robust quality assurance framework in accredited serological laboratories.