RESUMO
BACKGROUND: The aim of this study was to compare the usefulness of 3 different screening instruments (questionnaires) for the detection of cannabis use (CU) with biological markers in blood and hair. METHODS: Ninety-four students were recruited in October 2013. Participants filled out the Severity of Dependence Scale (SDS), the CAGE-AID ("Cut down Annoyed Guilty Eye-opener"-Adapted to Include Drugs), and ProbCannabis-DT questionnaires concerning their possible CU. Blood and hair samples were taken and analyzed by gas chromatography-mass spectrometry. Logistic regression (Nagelkerke R(2)) and receiver operating characteristic (ROC) curve analyses were performed. THCCOOH (Δ(9)-tetrahydrocannabinoic acid) plasma of ≥5 ng/mL and THC (Δ(9)-tetrahydrocannabinol) hair concentrations of ≥0.1 and ≥0.02 ng/mg were used as the gold standard for CU. The questionnaire results were compared with different concentration ranges for THCCOOH in plasma (<5, 5-75, and >75 ng/mL, indicating the intensity of use) and THC in hair (≥0.02 ng/mg, ≥0.1 ng/mg). RESULTS: The Nagelkerke R(2) for comparing the SDS, CAGE-AID, and ProbCannabis-DT with THCCOOH in plasma was 0.350, 0.489, and 0.335, respectively. The area under the ROC curve (95% confidence interval) was 0.772 (0.662-0.882), 0.797 (0.710-0.884), and 0.769 (0.669-0.870), respectively. Corresponding sensitivity/specificity were 70%/84%, 100%/59%, and 87%/67%, respectively. These values were similar to those compared to a 0.02 ng/mg THC cutoff in hair. CONCLUSIONS: Moderate agreement was found between all questionnaires and biomarkers of CU. The CAGE-AID and probCannabis-DT questionnaires were very sensitive, but less specific. SDS was less sensitive, but more specific.