A multi-center quality control study of different CA15-3 immunoassays

Area of Science:

• Clinical Chemistry
• Tumor Marker Analysis
• Quality Control in Diagnostics

Background:

• CA15-3 is a crucial tumor marker for monitoring breast cancer.
• Inter-laboratory variability and long-term assay stability are significant challenges in CA15-3 testing.
• Standardized quality control materials are essential for ensuring reliable diagnostic results.

Purpose of the Study:

• To evaluate the long-term performance and precision of CA15-3 assays using a multi-center quality control study.
• To assess the utility of liquid BIOREF CA15-3 control sera for inter-laboratory quality control.
• To investigate potential sources of variability in CA15-3 determinations over time.

Main Methods:

• A multi-center study involving 17 laboratories measuring CA15-3 using seven different assays on automated immunoanalyzers.
• Utilization of BIOREF low, medium, and high level control sera for quantitative analysis.
• Calculation of inter-assay imprecision (coefficient of variation) and assay linearity using concentration ratios.

Main Results:

• Mean CA15-3 values for control sera were determined: 19.3 ± 2.7 kU/l (low), 75.2 ± 11.4 kU/l (medium), and 162.9 ± 37.1 kU/l (high).
• Inter-assay coefficients of variation ranged from 2.9% to 15.5%, indicating varying levels of precision across methods and laboratories.
• Assay linearity was confirmed, and long-term monitoring revealed variability linked to calibration changes, but overall precision has significantly improved compared to data from 17 years prior.

Conclusions:

• Test-independent reference materials like BIOREF sera are effective for CA15-3 quality control.
• These controls enable laboratories to monitor long-term assay performance and detect calibration drift.
• The study demonstrates substantial advancements in CA15-3 assay precision over the past two decades, enhancing diagnostic reliability.