DEVELOPMENT AND PSYCHOMETRIC TESTING OF THE IBADAN LOW BACK PAIN DISABILITY SCALE

Abstract

Scales which are used for measuring healthcare outcomes are often developed in the context of the culture and environment of the people for which they were originally developed. Scales originally developed for Nigerian culture and environment are few and none exists for Low Back Pain (LBP). The aim of this study was to develop a Nigerian culture and environment-friendly LBP disability scale and investigate its psychometric properties. Items for the Ibadan Low Back Pain Disability Scale (ILBPDS) were devised through literature review, patients’ and experts’ interviews. The initial draft with 43 items was taken through content validation, pretesting, factor analysis and series of experts’ reviews before the final 18-item scale was produced. Response options were adapted from an existing scale (the Ibadan Knee/Hip Osteoarthritis Outcome Measure) and maximum obtainable score was 72. In this quasi-experimental study, psychometric testing of ILBPDS involved 142 patients with non-specific LBP (Experimental Group [EG]) and 142 age and sex-matched controls (Control Group [CG]) recruited through consecutive sampling from tertiary hospitals across Nigeria. The ILBPDS was completed by EG and CG; participants in EG also completed the Numerical Pain Rating Scale (NPRS) at baseline. ILBPDS was completed again by participants in the EG 48 hours after the initial assessment. Sixty-four participants in EG completed a 5-week physiotherapy programme and were assessed using the ILBPDS and NPRS. ILBPDS scores of EG and CG were compared using Mann Whitney-U test. Internal consistency was analysed using Cronbach’s α. Spearman correlation was used to correlate ILBPDS and NPRS scores of EG at baseline and post-intervention; and between changes in ILBPDS and NPRS scores of EG post-intervention. ILBPDS scores taken at baseline and 48 hours later were subjected to Intra Class Correlation (ICC). For EG, pre- and postv intervention ILBPDS scores and NPRS scores were compared using Wilcoxon signed rank test. Level of significance was set at 0.05. The age (48.6 ± 12.7 years) of participants in EG was comparable to that (48.2 ±12.3 years) of participants in CG. ILBPDS score of EG [55.2 (45.0-65.6)] was significantly higher than that of CG [21.4(20.0-24.3)](evidence of construct validity) and EG’s NPRS score correlated significantly with their ILBPDS score (r = 0.50; p= 0.001)at baseline and post intervention (r =0.35; p= 0.001)(evidence of divergent validity). ILBPDS scores at baseline [55.2 (45.0- 65.6)] and 48 hours later [51.8 (41.3-65.7) for participants in EG correlated significantly (ICC=0.80; p= 0.001) (evidence of test re-test reliability). Cronbach’s α for ILBPDS was 0.84 (evidence of internal consistency). Post-intervention ILBPDS score [36.5(30.0-49.4)] was significantly lower than the pre-intervention ILBPDS score [55.2 (45.0-65.6)](evidence for responsiveness).Post-intervention changes in ILBPDS and NPRS scores correlated significantly(evidence of responsiveness). The Ibadan Low Back Pain Disability Scale is valid, reliable, responsive and internally consistent for measuring disability in patients with non-specific low back pain and it is proposed for use in the Nigerian clinical setting.