Reliability of physical functioning tests in patients with low back pain: a systematic review

The aim of this study was to provide a comprehensive overview of physical functioning tests in patients with low back pain (LBP) and to investigate their reliability. A systematic computerized search was finalized in four different databases on June 24, 2017: PubMed, Web of Science, Embase, and MEDLINE. Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines were followed during all stages of this review. Clinical studies that investigate the reliability of physical functioning tests in patients with LBP were eligible. The methodological quality of the included studies was assessed with the use of the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) checklist. To come to final conclusions on the reliability of the identified clinical tests, the current review assessed three factors, namely, outcome assessment, methodological quality, and consistency of description. A total of 20 studies were found eligible and 38 clinical tests were identified. Good overall test-retest reliability was concluded for the extensor endurance test (intraclass correlation coefficient [ICC]=0.93–0.97), the flexor endurance test (ICC=0.90–0.97), the 5-minute walking test (ICC=0.89–0.99), the 50-ft walking test (ICC=0.76–0.96), the shuttle walk test (ICC=0.92–0.99), the sit-to-stand test (ICC=0.91–0.99), and the loaded forward reach test (ICC=0.74–0.98). For inter-rater reliability, only one test, namely, the Biering-Sörensen test (ICC=0.88–0.99), could be concluded to have an overall good inter-rater reliability. None of the identified clinical tests could be concluded to have a good intrarater reliability. Further investigation should focus on a better overall study methodology and the use of identical protocols for the description of clinical tests. The assessment of reliability is only a first step in the recommendation process for the use of clinical tests. In future research, the identified clinical tests in the current review should be further investigated for validity. Only when these clinimetric properties of a clinical test have been thoroughly investigated can a final conclusion regarding the clinical and scientific use of the identified tests be made.