Statistical comparisons of 0.08 g/100 ml fortified blood alcohol samples from 6-ml and 10-ml gray-top tubes

This experiment supplements the study, "Statistical comparisons of blood alcohol samples from 6-ml and 10-ml grey-top tubes". The initial study analyzed fortified samples for blood alcohol concentration (BAC) using two sizes of gray-top tubes: a 10-ml tube containing a nominal 1% sodium fluoride (NaF), a preservative, and a 6-ml tube containing 0.25% NaF, using the variables of time, storage temperature, fill volume, and concentration. From that study, paired t-tests determined no difference in BAC from data sets of the two tube sizes, however, Analysis of Variance, or ANOVA, testing determined the two tube sizes yielded different results at 0.08 g/100 ml. To investigate this potential disparity, this study fortified new samples at 0.08 g/100 and focused on two variables: fill volume and storage duration, while increasing the sample population (to n = 8). For this study, the two tube types yielded equivalent concentrations under the majority of conditions studied. Differences between the two tube types were found using paired t-test for the high-volume samples on Days 7 and 30; ANOVA yielded the same results but also determined one additional statistical difference for the Day 30 low-volume samples. However, the differences observed between tube sizes fall within standard deviation ranges established for the analytical method precision profile, indicating statistical differences are not analytically significant. Further studies are needed to investigate the comparability of the tubes under real-world conditions, under which oxygen and/or additives are not added during sample preparation steps or by usage of blood bank products.