The AUDIT questionnaire: choosing a cut-off score

A representation and interpretation of the area under a receiver operating characteristic (ROC) curve obtained by the "rating" method, or by mathematical predictions based on patient characteristics, is presented. It is shown that in such a setting the area represents the probability that a randomly chosen diseased subject is (correctly) rated or ranked with greater suspicion than a randomly chosen non-diseased subject. Moreover, this probability of a correct ranking is the same quantity that is estimated by the already well-studied nonparametric Wilcoxon statistic. These two relationships are exploited to (a) provide rapid closed-form expressions for the approximate magnitude of the sampling variability, i.e., standard error that one uses to accompany the area under a smoothed ROC curve, (b) guide in determining the size of the sample required to provide a sufficiently reliable estimate of this area, and (c) determine how large sample sizes should be to ensure that one can statistically detect differences in the accuracy of diagnostic techniques.

This study was conducted to estimate the psychometric properties of the questionnaire section of the Alcohol Use Disorders Identification Test (AUDIT) in a college sample using DSM-III criteria for alcohol abuse as the criterion standard. This alcohol screening test was developed for the 10 country AMETHYST project. In this young adult sample the instrument exhibited a sensitivity of .84 and specificity of .71 when utilizing the recommended cut-off score of 11. The 10-item questionnaire section of the AUDIT appears to have important advantages over other alcohol screening instruments such as the CAGE and the MAST.