Urdu version of Oswestry disability index; a reliability and validity study

Oswestry Disability Index (ODI) is broadly used in clinical and research settings for assessing the disability level in patients with lumbar radiculopathy but it has not been translated into Urdu language according to the pre-established translation guidelines as well as the validity and reliability of ODI Urdu version has not been tested yet. The aim of this study was to translate ODI in native Urdu language (ODI-U) according to recommended guidelines and to measure its psychometric properties in Urdu speaking patients suffering from lumber radiculopathy.

Out of 108 participants, 54 were healthy (who filled ODI-U) and 54 were patients of lumber radiculopathy. The patients were administered through ODI-U, visual analogue scales for disability (VAS disability), pain intensity (VAS pain) and SF-36 at baseline and after 3 days. Reliability was investigated through test-retest method, internal consistency, standard error of measurement (SEM) and smallest detectable change (SDC). ODI-U was assessed for exploratory factor analysis, construct (convergent and discriminative) validity and content validity. Alpha level < 0.05 was considered statistically significant and psychometric standards were evaluated contrary to priori hypothesis.

ODI-U revealed excellent test-retest reliability for total score (ICC_2,1 = 0.95) and for all item (ICC_2,1 = 0.72-0.98). Cronbach's alpha of 0.89 showed excellent internal consistency and moderate correlation between ODI-U total score and each item through spearman's correlation coefficient (r = 0.51-0.76). One factor structure was created, explaining 52.5% variance. There was no floor and ceiling effect of total ODI-U score. Content validity was assessed through conducting interviews with patients and incorporating expert's opinions. The discriminative validity was measured by independent sample t-test, where significant difference between healthy and patients (P < 0.001) was observed. The convergent validity was evaluated through Pearson's correlation showing moderate positive correlation of ODI-U with VAS pain (r = 0.49) and VAS disability (r = 0.51) but moderate negative correlation with all SF-36 domains (r = - 0.43to - 0.63).

ODI-U showed adequate psychometric properties. ODI-U was found to be a reliable and a valid tool to measure the level of disability in Urdu-speaking patients with lumber radiculopathy.