Do breath tests really underestimate blood alcohol concentration?

Area of Science:

• Forensic toxicology
• Analytical chemistry

Background:

• Breathalyzer devices are commonly used to estimate blood alcohol concentration (BAC).
• Previous studies suggested underestimation of BAC by breath tests in the postabsorptive state.

Purpose of the Study:

• To re-evaluate the accuracy of breath test results for blood alcohol concentration (BAC) in the postabsorptive state.
• To investigate the timing of the postabsorptive state relative to alcohol consumption.

Main Methods:

• Reanalysis of existing data on breath test versus actual BAC measurements.
• Comparison of reanalyzed data with other relevant studies.

Main Results:

• Reanalysis indicated 77% of subjects had their BAC underestimated, and 23% overestimated, contradicting initial reports.
• Further analysis revealed 68% underestimated, 16% were acceptably close, and 16% overestimated.
• The fully postabsorptive state may occur later than three hours after drinking.

Conclusions:

• Breath test results may overestimate actual BAC for extended periods after peak levels are reached.
• The timing of the postabsorptive state significantly impacts breathalyzer accuracy.
• Rethinking the interpretation of breathalyzer results in the postabsorptive phase is warranted.