Rationalization of outcome scores for low back pain: the Oswestry disability index and the low back outcome score

Abstract

The two commonly used questionnaires to assess low back pain are the low back outcome score (LBOS) and the Oswestry disability index (ODI). This study aims to identify unique questions and remove redundant questions to develop a composite questionnaire. Eighty-seven consecutive patients attending the practice of a single spinal surgeon completed both the ODI and the LBOS as part of their initial assessment. Both questionnaires were analysed to eliminate questions that exhibit floor-ceiling bias and questions that are interdependent and correlate strongly. Total scores and the scores obtained for each question were then compared (Spearman's rho). A principal axis factor analysis using a varimax rotation was performed to reduce data and identify questions that were interdependent. Using these data, a composite questionnaire was proposed that would minimize overlap in clinical data. Eighty-seven patients completed the LBOS and ODI. The mean age is 54, with a range between 18 and 80. The male to female ratio was 50:37. By eliminating questions that contain biases and overlap in clinical data, the composite questionnaire contains 11 questions. From LBOS; housework, dressing, sleeping, sitting, walking and travelling. From the ODI; pain, standing, social life and lifting. Analysis of the questionnaires identified eight questions that were similar in both questionnaires. Two questions were included that were unique to each questionnaire. The proposed composite questionnaire is of similar size as the original questionnaires and retains questions that are unique to each other while eliminating questions that are redundant and exhibit bias.