Assessing pain intensity in people from non-western countries: A multicenter study comparing four pain scales in adults with musculoskeletal pain in Bhutan.

Although the Numerical Rating Scale (NRS) is commonly recommended for use in research and clinical practice internationally, recent research in non-western countries questions its utility in some countries. We aimed to evaluate validity and utility of four commonly used pain intensity measures in a sample of participants with musculoskeletal pain in Bhutan. Two hundred forty-seven adults with musculoskeletal pain visiting three hospitals rated their one-week recalled worst and average pain using all four scales, and indicated their preferred scale. For analysis, participant responses were classified as being a correct or an incorrect response, where an "incorrect response" was defined as a response that did not meet pre-defined criteria. All four scales demonstrated adequate construct validity. The VAS and NRS had significantly higher incorrect response rates (9% each) than the other scales. Participants who were older and with less education had higher rates of incorrect responses on the NRS and VAS. The FPS-R (45%) was the most preferred scale, followed by the NRS (26%); there were no significant differences in preference rates between the VRS (15%) and VAS (5%). The findings suggest that the FPS-R should be used to assess pain intensity in Bhutanese people with musculoskeletal pain, especially in individuals with no formal education. PERSPECTIVE: This study evaluated the utility and validity of four commonly used pain intensity scales in Bhutan. The findings could help clinicians and researchers select the most appropriate scale for measuring pain intensity in Bhutanese individuals.