Development and testing of new candidate psoriatic arthritis screening questionnaires combining optimal questions from existing tools.
Coates LC., Walsh J., Haroon M., FitzGerald O., Aslam T., Al Balushi F., Burden AD., Burden-Teh E., Caperon AR., Cerio R., Chattopadhyay C., Chinoy H., Goodfield MJD., Kay L., Kelly S., Kirkham BW., Lovell CR., Marzo-Ortega H., McHugh N., Murphy R., Reynolds NJ., Smith CH., Stewart EJC., Warren RB., Waxman R., Wilson HE., Helliwell PS.
OBJECTIVE: Several questionnaires have been developed to screen for psoriatic arthritis (PsA), but head-to-head studies have found limitations. This study aimed to develop new questionnaires encompassing the most discriminative questions from existing instruments. METHODS: Data from the CONTEST study, a head-to-head comparison of 3 existing questionnaires, were used to identify items with a Youden index score of ≥0.1. These were combined using 4 approaches: CONTEST (simple additions of questions), CONTESTw (weighting using logistic regression), CONTESTjt (addition of a joint manikin), and CONTESTtree (additional questions identified by classification and regression tree [CART] analysis). These candidate questionnaires were tested in independent data sets. RESULTS: Twelve individual questions with a Youden index score of ≥0.1 were identified, but 4 of these were excluded due to duplication and redundancy. Weighting for 2 of these questions was included in CONTESTw. Receiver operating characteristic (ROC) curve analysis showed that involvement in 6 joint areas on the manikin was predictive of PsA for inclusion in CONTESTjt. CART analysis identified a further 5 questions for inclusion in CONTESTtree. CONTESTtree was not significant on ROC curve analysis and discarded. The other 3 questionnaires were significant in all data sets, although CONTESTw was slightly inferior to the others in the validation data sets. Potential cut points for referral were also discussed. CONCLUSION: Of 4 candidate questionnaires combining existing discriminatory items to identify PsA in people with psoriasis, 3 were found to be significant on ROC curve analysis. Testing in independent data sets identified 2 questionnaires (CONTEST and CONTESTjt) that should be pursued for further prospective testing.