– The purpose of this paper is to test the discriminative validity of the Substance Use Beliefs Questionnaire (SUBQ) with alcohol dependent users, by assessing if the new tool can successfully differentiate between two extreme groups.
– The criterion used to select the two extreme groups was participation or not in treatment for alcohol dependence. Score of the Severity of Alcohol Dependence Questionnaire (SADQ) was used as a secondary confirmation criterion of extreme difference.
– In all, 98 staff and 94 people in treatment for alcohol dependence were recruited. The treatment group scored 30.83 higher than the control on SADQ, 10.76 on positive and 28.98 on negative expectancies. Negative expectancies score had correctly classified 88.5 per cent and positive expectancies score only 66 per cent of the original grouped cases. The area under the Receiver Operating Characteristics (ROC) curve for negative expectancies was 0.94 (very good) with a cut-off point of 43.5 with 89 per cent sensitivity and 92 per cent specificity. The area under the ROC curve for positive expectancies was 0.73 (fair). Due to the shape it was difficult to identify a cut-off point.
– The results support the discriminative validity of the negative expectancies sub scale of the SUBQ between two extreme groups. With only the use of negative expectancies score participants could be classified correctly to those of the control and those of the treatment group.
– SUBQ is the first tool to measure outcome expectancies across substances, facilitating relevant research with poly substance users. Future research needs to explore the discriminative validity of the tool with the other three substance groups (smokers, stimulant and opioids users), involved in the development and validation of the SUBQ.
