Comparison of Breath- and Blood-Alcohol Concentrations in a Controlled Drinking Study.

In this work, 114 volunteers were dosed with 80-proof liquor to produce peak blood-alcohol concentration (BAC) or breath-alcohol concentration (BrAC) of 0.040-0.080 g/100 mL blood or g/210 L breath. This was followed by a 30 minute deprivation period before simultaneous blood and breath samples were collected and the alcohol concentration quantified. BAC was determined by gas chromatography with flame ionization detection and BrAC by a dual-sensor Intox EC/IR II instrument. Paired Student t-tests showed that differences between paired blood- and breath-alcohol results differed significantly. Results from these two measurement methods are highly correlated and, on average, measured BAC was 11.3% greater than BrAC. There were 10 instances of BrAC being greater than the corresponding BAC, and the average difference between these two values was 0.0059 g/100 mL. Agreement plots of coupled BAC and BrAC revealed a mean bias of 0.00754 g/100 mL and 95% limits of agreement (LOA) at -0.00705 and 0.0221 g/100 mL. Once BrAC values were truncated to the hundredths place as required by Wisconsin state statute, only three participants had greater BrAC than corresponding BAC, with an average difference between these values of 0.008 g/100 mL. Agreement plots with truncated BrAC values gave a mean bias of 0.0120 g/100 mL and 95% LOA at -0.00344 and 0.0275 g/100 mL. Data showed that typically, blood samples had greater alcohol concentrations than corresponding breath values. Differences were exacerbated by Wisconsin's statutory requirement that reported breath alcohol measurements be truncated to the hundredths place, whereas blood has no corresponding mandate.