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Implementation of a Blind Quality Control Program in Blood Alcohol Analysis.
Jackeline Moral1, Callan Hundl1, Dayong Lee1
1Houston Forensic Science Center, 500 Jefferson Street, 13th Floor, Houston, USA.
Journal of Analytical Toxicology
|August 20, 2019
Summary
Blind quality control (BQC) in blood alcohol analysis ensures lab reliability by simulating real cases. HFSC
Area of Science:
- Forensic Science
- Analytical Chemistry
- Laboratory Quality Assurance
Background:
- Declared proficiency tests can be biased as analysts know they are being tested.
- Blind quality control (BQC) simulates real casework to mitigate bias and assess laboratory performance.
- HFSC implemented a BQC program for blood alcohol analysis in September 2015.
Purpose of the Study:
- To evaluate the effectiveness of a blind quality control program in blood alcohol analysis.
- To assess the reliability of laboratory procedures and casework under realistic conditions.
- To monitor the performance of blood alcohol concentration (BAC) measurements over time.
Main Methods:
- HFSC submitted 317 blind cases (89 negative, 228 positive) with target BACs between 0.08 and 0.25 g/100 mL.
- Blood samples were analyzed using headspace gas chromatography with dual-flame ionization detectors (HS-GC-FID).
- Multiple linear regression analysis was used to compare BAC differences across target concentrations, analysts, instruments, and pipettes.
Main Results:
- All negative samples correctly yielded 'no ethanol detected'.
- Mean BACs for positive samples ranged from 0.075 to 0.249 g/100 mL, with average differences from targets between -0.4% and -6.3%.
- The 0.08 g/100 mL target showed a significantly larger % difference compared to higher targets; no concentration-dependency was found among higher targets.
Conclusions:
- The BQC program demonstrated the reliability of blood alcohol analysis methods at HFSC.
- The program identified a statistically significant difference in accuracy at the 0.08 g/100 mL target concentration.
- Implementation of BQC improved laboratory processes, validated method reliability, and enhanced staff confidence in court testimony.
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