Inter-rater reliability and cross-validation of lumbar stability test

Abstract

Background: Clinical lumbar stability test can be used to assess individuals’ ability to control their lumbar spine during limb movements. However, inter-rater reliability and validity has not previously been investigated. Therefore, this study aimed to (1) establish inter-rater reliability of lumbar stability test, and (2) cross-validate the lumbar stability test using lab-based equipment as a reference standard.Methods: Twenty-nine healthy university students were recruited. Two fourth year physical therapy students performed lumbar stability test. Lumbar stability levels were used to determine inter-rater reliability using kappa statistics. Then, the participants were asked to perform two trials of 30-s seated balance tests on an unstable chair in eye-open and eye-closed conditions. These trunk neuromuscular control data, including 95% confidence ellipse area (CEA), root-mean-square error along X and Y axes (RMSEx and RMSEy, respectively), were used to cross-validate the lumbar stability test using Spearman’s correlation.Results: Kappa statistics revealed poor to almost perfect agreement (0–1.00). When adjusting for prevalence and bias, inter-rater reliability were fair to almost perfect (0.31–0.59). CEA, RMSEx and RMSEy were greater in eye-closed condition (8.81, 0.30 and 0.48, respectively) comparing with eye-open condition (2.79, 0.16 and 0.26, respectively). Correlation between lumbar stability level and trunk neuromuscular control were fair (r = –0.31–0.34) in eye-open condition and weak (r = –0.14–0.18) in eye-closed condition.Conclusion: Lumbar stability test should be refined to improve inter-rater reliability. Lumbar stability level does not completely represent trunk postural control. Clinicians should use this test with caution.