Supplementary Material for: Validation of the Problematic Khat Use Screening Test: A Cross-Sectional Study

Aim: The study aimed to evaluate the psychometric properties of the Problematic Khat Use Screening Test (PKUST-17) in Ethiopia. Methods: A validation study of PKUST-17 was carried out among 510 khat users, using a house-to-house survey. Confirmatory factor analysis and 2-parametric item response theory (IRT) were used to evaluate the construct validity of PKUST-17. We also used Spearman’s rank-order correlation coefficient and other test statistics to assess the convergent validity of PKUST-17 with depression symptoms, functional impairment, and other characteristics of participants. We generated latent classes of problematic khat use using latent profile analysis (LPA) and validated the classes using multinomial logistic regression. Results: The data confirm the unidimensional model of the PKUST-17. The internal consistency of PKUST-17 was excellent (Cronbach’s alpha = 0.93). IRT discrimination parameters indicated that each item had a strong ability to distinguish participants across the spectrum of problematic khat use (α thresholds range from 1.02 to 2.9). The items were fairly or moderately severe to be endorsed by participants (β thresholds vary from 1.43 to 5.57). The LPA identified three latent classes which have severity differences: mild (34%), moderate (34%), and severe (32%) problematic khat use. Depression symptoms, functional impairment, and other khat use patterns were also associated with moderate and severe problematic khat use class membership compared to mild problematic khat use class. Conclusion: We found that the PKUST-17 is a culturally appropriate, brief, easy to use, and psychometrically sound screening test. PKUST-17 can be used to screen khat users with different levels of risk for providing stepped care at different healthcare levels, including integration of services in primary care. Future studies need to test the predictive capacity of the PKUST-17 for khat-related harms.研究目的：本研究旨在评估埃塞俄比亚境内问题性恰特草使用筛查量表（Problematic Khat Use Screening Test，PKUST-17）的心理测量学特性。 研究方法：本研究针对510名恰特草使用者开展PKUST-17的验证研究，采用入户调查方式。研究使用验证性因子分析与2参数项目反应理论（Item Response Theory，IRT）评估PKUST-17的结构效度；同时采用斯皮尔曼等级相关系数及其他检验统计量，分析PKUST-17与抑郁症状、功能损害及受试者其他特征的聚合效度。本研究还通过潜在剖面分析（Latent Profile Analysis，LPA）生成问题性恰特草使用的潜在类别，并采用多项逻辑回归对上述类别进行验证。 研究结果：数据证实PKUST-17符合单维模型结构。PKUST-17的内部一致性表现优异（克朗巴赫α系数=0.93）。项目反应理论区分参数显示，各条目均具备较强的区分能力，可精准区分不同程度问题性恰特草使用的受试者（α阈值区间为1.02至2.9）；条目作答难度处于中等水平，β阈值区间为1.43至5.57。潜在剖面分析识别出3个存在严重程度差异的潜在类别：轻度（34%）、中度（34%）与重度（32%）问题性恰特草使用。相较于轻度问题性恰特草使用类别，中度与重度类别的受试者其抑郁症状、功能损害及其他恰特草使用模式均与类别归属显著相关。 研究结论：本研究证实PKUST-17是一款具备文化适配性、简洁易用且心理测量学性能优良的筛查工具。PKUST-17可用于筛查不同风险等级的恰特草使用者，以在各级医疗卫生机构开展分级照护，包括将其整合至基层医疗卫生服务中。未来研究可进一步检验PKUST-17对恰特草相关危害的预测能力。