Inter-rater reliability of three standardized functional tests in patients with low back pain

Background: Of all patients with low back pain, 85% are diagnosed as "non-specific lumbar pain". Lumbar instability has been described as one specific diagnosis which several authors have described as delayed muscular responses, impaired postural control as well as impaired muscular coordination among these patients. This has mostly been measured and evaluated in a laboratory setting. There are few standardized and evaluated functional tests, examining functional muscular coordination which are also applicable in the non-laboratory setting. In ordinary clinical work, tests of functional muscular coordination should be easy to apply. The aim of this present study was to therefore standardize and examine the inter-rater reliability of three functional tests of muscular functional coordination of the lumbar spine in patients with low back pain. Methods: Nineteen consecutive individuals, ten men and nine women were included. ( Mean age 42 years, SD +/- 12 yrs). Two independent examiners assessed three tests: "single limb stance", "sitting on a Bobath ball with one leg lifted" and "unilateral pelvic lift" on the same occasion. The standardization procedure took altered positions of the spine or pelvis and compensatory movements of the free extremities into account. The inter-rater reliability was analyzed by Cohen's kappa coefficient (kappa) and by percentage agreement. Results: The inter-rater reliability for the right and the left leg respectively was: for the single limb stance very good (kappa: 0.88-1.0), for sitting on a Bobath ball good (kappa: 0.79) and very good (kappa: 0.88) and for the unilateral pelvic lift: good (kappa: 0.61) and moderate (kappa: 0.47). Conclusion: The present study showed good to very good inter-rater reliability for two standardized tests, that is, the single-limb stance and sitting on a Bobath-ball with one leg lifted. Inter-rater reliability for the unilateral pelvic lift test was moderate to good. Validation of the tests in their ability to evaluate lumbar stability is required.