Development of a Problematic Khat Use Screening Test (PKUST-17) in Ethiopia: Classical Test Theory and Item Response Theory Analysis

Abstract

Problematic khat use has been poorly defined and measured. This study aimed to develop a problematic khat use screening tool in the Gurage Community, South-central Ethiopia. We have used a series of methods (systematic review, qualitative study and cognitive interviewing) to generate a pool of items for problematic khat use screening tool. Classical test theory (inter-item, and item-total correlation, intraclass correlation, Cronbachalpha and exploratory factor analysis) and a 2-parameter item response theory statistics were used for initial psychometric evaluation of the scale. Initially, we developed a pool of 50 items. IRT analysis indicated that the item, ''during the past three months, how often have you experienced irritability when you didn't chew khat?” showed the highest discrimination (α thresholds =2.44). The item about “during the past three months, to what extent have you failed to do what was normally expected of you because of your use of khat? was the most difficult (first β thresholds =0.25) item, which was the only positive coefficient. The test information function graph depicts that the scale provided a lot of information in the latent trait's moderate range. We found that employing series of methods is very important for item selection and refinement. We developed a Problematic Khat Use Screening Test with 17 items which will have a good utility for the general population or primary health care setting more than for the clinical population. Future studies should do full-scale validation of the scale.