Are there gender-related differences in the psychometric properties of the Oswestry Disability Index?

Abstract

Despite the wide body of research on the properties of the Oswestry Disability Index (ODI), only a few studies have investigated whether ODI scores can be interpreted similarly in both genders. A few previous studies suggested that the ODI may behave differently in different populations, e.g. in different age groups. The objective was to investigate gender-related differences in the psychometric properties of the ODI amongst patients with chronic low back pain. Observational cross-sectional cohort study. University outpatient Physical and Rehabilitation Medicine clinic. Consecutive patients seen in an outpatient Physical and Rehabilitation Medicine clinic at a university hospital between April 2014 and February 2017. Internal consistency was evaluated using Cronbach's alpha. Factor structure was investigated using exploratory factor analysis. Gender-related differences in psychometric properties of ODI items were assessed using item response theory analysis. The study included 912 patients, 579 women (63%), with an average age of 45.8 (SD 14.2) years old. The Cronbach's alpha for both genders was good at 0.88. The discrimination abilities of all 10 ODI items were mostly high to perfect for both men and women with only small fluctuations. The item information function curves were similar for most of the items. Exploratory factor analysis resulted in a unidimensional one-factor structure for both genders. The ODI appears to be a similarly unidimensional and internally consistent questionnaire in both genders without any substantial variability in the items' difficulty and discrimination. The ODI produces psychometrically similar results in both genders. Small and clinically hardly significant gender-related differences in the properties of ODI can be neglected.