An international proficiency study with the tumor marker CA 125

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Quality Assurance

Background:

• Reliable laboratory test results are crucial for patient diagnosis and management.
• Quality assurance programs are essential for validating the accuracy of diagnostic tests.
• The CA 125 assay is a significant biomarker, necessitating rigorous performance evaluation.

Purpose of the Study:

• To assess the performance and reliability of the CA 125 test system.
• To evaluate the effectiveness of proficiency testing in identifying assay variability.
• To establish a concentration-dependent performance profile for the CA 125 assay.

Main Methods:

• Proficiency testing conducted in five university laboratories over three years (1984-1987).
• Utilized five distinct reference materials for CA 125 analysis.
• Evaluated a total of 301 assays to establish performance profiles and precision.

Main Results:

• Intra-assay precision ranged from 4.8% to 11.5%; inter-assay precision ranged from 13.6% to 19.1%.
• Significant batch-dependent variations were observed, which were not flagged by manufacturer-supplied kit controls.
• No systematic drift was detected over the study period, indicating excellent stability of frozen reference materials.

Conclusions:

• Strict quality assurance programs, including proficiency testing, are vital for ensuring the reliability of CA 125 laboratory test results.
• Manufacturer kit controls may not adequately detect critical batch-to-batch variations in the CA 125 assay.
• The stability of properly stored reference materials is confirmed, supporting their use in quality control.