The Oswestry Disability Index for low back pain: Translation into Persian and validation within a Persian-speaking population – an update

BackgroundThe Oswestry Disability Index (ODI) is widely used to assess disability due to low back pain. Existing Persian versions were developed in Iran only and do not reflect the full linguistic and cultural diversity of Persian speakers worldwide.ObjectiveThis study had two aims: (1) to provide an updated, culturally inclusive Persian translation and adaptation of the ODI following the Beaton cross-cultural adaptation guidelines, and (2) to evaluate, per the COSMIN taxonomy of measurement properties, its reliability and inter-method agreement across diverse Persian speakers. The translation was refined through a structured five-stage process and reviewed by native speakers from Iran, Afghanistan, Tajikistan, and diaspora communities.Methods578 participants with low back pain (aged 18-86) completed the Persian ODI twice in a single session, once alone (self-administered) and once with an interviewer, to assess inter-method agreement. Reliability and agreement were analyzed using paired t-test, Wilcoxon test, Cohen's d, ICC, and Bland-Altman limits of agreement.ResultsMean ODI scores were 13.83 ± 12.06 (Alone) and 14.55 ± 12.46 (With interviewer). ICC(2,1) was 0.95, indicating excellent reliability, while Cohen's d = 0.18 indicated a small, non-significant effect. Bland-Altman limits of agreement ranged from -6.91 to +8.35.ConclusionThe updated Persian ODI, developed and evaluated per established cross-cultural adaptation and measurement-property guidelines, shows excellent reliability and agreement across diverse Persian-speaking populations. Interviewer administration yielded slightly higher scores, but the difference was small and not clinically significant. This version can be confidently used for clinical and research purposes across Persian-speaking communities worldwide.