Validity of the Dutch modified painDETECT questionnaire for patients with hip or knee osteoarthritis

Background: The modified painDETECT questionnaire (PDQ) is a self-reported questionnaire to discriminate between nociceptive and neuropathic-like pain in patients with knee/hip osteoarthritis (OA). This study aims to assess the structural and construct validity of this questionnaire. Methods: Confirmatory factor analysis and hypothesis-testing was used. For 168 patients, predefined hypotheses were formulated on the correlation between the modified painDETECT and several other questionnaires, and in a subsample of 46 with pain pressure thresholds (PPTs). Results: Two principal components were confirmed. The pain pattern item did not load on any component. Eighty per cent of the hypotheses on the correlation between modified PDQ and the questionnaires were met, as were 50% concerning PPTs measurements. Conclusions: This study is the first to assess structural and construct validity of the modified PDQ knee/hip by using factor analysis and hypothesis-testing. This questionnaire seems to reflect neuropathic-like pain symptoms experienced by hip/knee OA-patients with adequate validity. The item on pain pattern might not reflect the construct. More than 75% of the predefined hypotheses regarding the modified PDQ and the other questionnaires were met. Only 50% of the hypotheses on PPTs measurements were met, probably due to heterogeneity and limited size of this subsample.