Assessing the Functional Status of Patients with Chronic Pain—Cross Cultural Adaptation and Psychometric Properties of the Serbian Version of the Pain Disability Questionnaire

The Pain Disability Questionnaire (PDQ) has established itself as a leading patient-reported outcome measure for assessing both mental and physical components of pain-related disability. The current study aimed to translate the PDQ into Serbian and validate its psychometric properties. Following a standard translation process, a total of 554 chronic pain patients (average age 55.37 ± 12.72 years; 375 (67.5%) females) completed the PDQ-Serb, Oswestry Disability Index (ODI), Short Form-36 (SF-36), pain intensity rating and a six-minute walk test (6MWT). Responsiveness was examined in a subsample of 141 patients who completed an inpatient rehabilitation program. The internal consistency of the PDQ-Serb was excellent (Cronbach α = 0.92) and test-retest reliability was favorable (ICC = 0.87). Factor analyses found a bifactor model to be the best fit (CFI = 0.97: TLI = 0.96: RMSEA = 0.05; SRMR = 0.03). Statistically significant Pearson’s coefficient correlations (p < 0.001) were found between the PDQ-Serb and ODI (r = 0.786), SF-36 Physical Components summary (r = −0.659), SF-36 Mental Components summary (r = −0.493), pain intensity rating (r = 0.572), and 6MWT (r = −0.571). Significant post-treatment improvements following inpatient rehabilitation were found with the PDQ-Serb (p < 0.001; effect size 0.431) and other clinical variables (p < 0.001; effect sizes from 0.367 to 0.536). The PDQ-Serb was shown to be a reliable and valid self-report instrument for the evaluation of pain-related disability.