Beyond proficiency testing: Leveraging commutable External Quality Assessment data to harmonize tumor markers and refine medical decision points.

BackgroundSerum tumor markers such as carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), and prostate-specific antigen (PSA) are crucial to clinical decision-making based on defined medical thresholds. However, significant inter-method variability and lack of harmonization limit result comparability and hinder consistent application of international guidelines.ObjectiveThis letter proposes an expanded role for External Quality Assessment (EQA) programs as active drivers of assay harmonization beyond conventional proficiency testing.MethodsThis proposal draws on recent studies evaluating the commutability of frozen human serum pools (FSPs) from the Korean Association of External Quality Assessment Service (KEQAS) and findings from EQA-based harmonization simulations. It demonstrated that harmonization of tumor markers such as CA 15-3 and CEA, is achievable.ResultsKEQAS FSPs demonstrated commutability for AFP, CEA, and total PSA across major diagnostic platforms. Simulation results indicated that "in silico" recalibration substantially reduced inter-method variability; for example, the bias range for CA 15-3 was reduced from [-29.28%, 9.86%] to [-0.09%, 0.12%], and recalibrating outlier methods for CEA improved the alignment also.ConclusionsEQA programs can serve as practical harmonization hubs by leveraging commutable materials and implementing EQA-driven recalibration. Such approaches can help that medical decision points, retain consistent clinical significance across diverse analytical systems.