Criterion Validity of the Problematic Khat Use Screening Tool (PKUST-17) in Ethiopia

The use of amphetamine-type stimulants such as khat has been spreading quickly in eastern parts of Africa, the Arabian region and Asia. However, screening for the provision of early intervention has been inadequate, primarily because of the lack of culturally acceptable and valid screening tools.

To evaluate the the accuracy of the Problematic Khat Use Screening Tool (PKUST-17) in screening for khat use disorder against the DSM-5 criteria for substance use disorder.

A cross-sectional validation study was conducted in Ethiopia from February to December 2018, among a randomly selected sample of 506 individuals. The study subsample comprised 236 participants. We used the DSM-5 criteria for stimulant use disorders as the standard for determining the criterion validity and optimal cut-off score for the PKUST-17, using the receiver operating characteristic (ROC) curve. The DSM-5 criteria for substance use disorders were examined by researchers in a subsample of 232 participants. The PKUST-17 uses a five-point Likert scale (0-4), with total scores ranging from 0 to 68. At the optimal cut-off scores, sensitivity and specificity were determined. In addition, we conducted multivariate logistic regression analysis to evaluate potential convergent validity of the tool.

The area under the ROC curve showed good performance of the PKUST-17 (0.78, 95% CI 0.70-0.85, P < 0.001). A cut-off score above 17 demonstrated a sensitivity of 72% and specificity of 73%. The positive predictive value was 77.6% and the negative predictive value was 65.8% in identifying stimulant use disorder, as per the DSM-5 criteria. Among others, problematic khat use was significantly associated with higher World Health Organization Disability Assessment Schedule 2.0 scores (adjusted odds ratio 1.78, 95% CI 1.04-3.03, P < 0.01) and more depressive symptoms (adjusted odds ratio 4.10, 95% CI 2.36-7.12, P < 0.05).

We found that the PKUST-17 is a valid tool for screening for khat use disorder against the DSM-5 criteria for substance use disorder, and identifying high-risk problematic khat users.