Background Patients with knee osteoarthritis (KOA) may have pain sensitization which is a potential risk factor for chronic pain after total knee replacement surgery (TKR). A neuropathic pain questionnaire may facilitate the identification of patients with KOA who has central sensitization.
Objectives We aim to evaluate the validity and reliability of the Singapore Chinese version of the painDETECT questionnaire (PDQ-Chi).
Methods The PDQ-Chi was cross-culturally adapted from the source English version with forward and backward translation according to standard guidelines, followed by cognitive debriefing in ten patients with KOA. The PDQ-Chi was administered to consecutive KOA patients enlisted for TKR in two weeks' time. The construct validities of the 7-items and 9-items PDQ-Chi were evaluated in comparison with the pressure pain threshold measured at medial knee joint line (the side that is going for TKR), and the volar area of right forearm. Test retest reliability was assessed by intraclass correlation coefficient (ICC) and classification consistency (proportion with no change in pain phenotype), in a subset of patients on day of TKR.
Results 165 patients (82.4% women, mean age 67.5 ± 7.8 years) were recruited to the study. The patients generally had low scores for PDQ-Chi (mean 4.9 ± 3.9). Only one patient had neuropathic pain as classified by PDQ-Chi (score ≥19). The Cronbach's alpha of the 7-items and 9-items PDQ-Chi were 0.60 and 0.58 respectively. Factor analysis of the 7-items PDQ-Chi revealed a 2-factor structure that explained 48% of total variance. The 9-items total PDQ-Chi scores correlated with pain scores, but not pressure pain threshold of knee or forearm. The PDQ-Chi did not correlate with the hypothesized trait of measurement. 17 patients administered the PDQ-Chi a second time on the day of TKR. The ICC of the 7-items and 9-items PDQ-Chi was 0.59 and 0.50, respectively; while the classification consistency of the 9-items PDQ-Chi was 94%.
Conclusions In this group of patients with KOA enlisted for TKR, both the 7-items and 9-items of PDQ-Chi were suboptimal in internal consistency and hypothesis testing. Using the 9-items PDQ-Chi with cut-offs as screening instrument for neuropathic pain, it had good classification consistency. Further studies with larger sample size are required for criterion validity.
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Disclosure of Interest None declared