Evaluating the variability of duplicate breath alcohol analyses as a function of subject age

The influence of the person's age upon reproducibility in duplicate breath alcohol analyses is investigated. A total of n = 30,324 duplicate results (with both > or = 0.01 g/210L) were selected and divided into eight age groups from 10-19, 20-29, and up through 80+. Two duplicate agreement criteria, +/- 10% of the mean and +/- 0.02 g/210L, were evaluated according to age. A X2 trend analysis was employed and resulted in: +/- 10% of mean criteria, P < 0.001 and +/- 0.02 g/210L criteria, P > 0.05. The proportions of duplicates not conforming to the two agreement standards along with 95% confidence intervals were: +/- 10% of mean, 0.026 (0.024 to 0.028) and +/- 0.02 g/210L, 0.052 (0.050 to 0.054). Depending on the agreement criteria selected there will be proportional differences, but neither appears to be importantly influenced by the subject's age. The breath sampling criteria employed in the instrument studied does not appear to inhibit acceptable agreement, even in elderly subjects where the risk of respiratory disfunction increases.