What is the role of laboratory QA/QC in clearance testing?

• A. To expedite sample processing by skipping blanks
• B. To document chain of custody only
• C. To report only final results
• D. To ensure accuracy and precision through method blanks, field blanks, sample duplicates, instrument calibration, and proficiency testing

Answer: (D)

Quality assurance and quality control in clearance testing focus on making sure the results are accurate, precise, and defensible so that clearance decisions are trustworthy. This is achieved by built-in checks that catch contamination, measurement errors, and variability. Method blanks reveal whether reagents or the lab environment are introducing contaminants into the analysis. Field blanks show if contamination was picked up during sampling or transport. Sample duplicates test precision by comparing two portions of the same sample to see how consistent the measurements are. Instrument calibration ensures the analytic instrument provides measurements that match known standards, preventing biased results. Proficiency testing evaluates lab performance by comparing results with external benchmarks, confirming the lab can reproduce accurate results over time and against peer labs. Together, these QA/QC measures ensure the data truly reflect the contaminant levels at a site, supporting safe and compliant clearance decisions. Skipping blanks to speed processing or focusing only on documenting custody or reporting final results would undermine the reliability of the data, even though those activities have their own importance.