Objective: Systematic reviews of prognostic factors for low back pain vary substantially in design and conduct. The objective of this study was to identify, describe, and synthesize systematic reviews of low back pain prognosis, and explore the potential impact of review methods on the conclusions.
Study design and setting: We identified 17 low back pain prognosis reviews published between 2000 and 2006. One reviewer extracted and a second checked review characteristics and results. Two reviewers independently assessed review quality.
Results: Review questions and selection criteria varied; there were both focused and broad reviews of prognostic factors. A quarter of reviews did not clearly define search strategies. The number of potential citations identified ranged from 15 to 4,458 and the number of included prognosis studies ranged from 3 to 32 (of 162 distinct citations included across reviews). Seventy percent of reviews assessed quality of included studies, but assessed only a median of four of six potential biases. All reviews reported associations based on statistical significance; they used various strategies for syntheses. Only a small number of important prognostic factors were consistently reported: older age, poor general health, increased psychological or psychosocial stress, poor relations with colleagues, physically heavy work, worse baseline functional disability, sciatica, and the presence of compensation. We found discrepancies across reviews: differences in some selection criteria influenced studies included, and various approaches to data interpretation influenced review conclusions about evidence for specific prognostic factors.
Conclusion: There is an immediate need for methodological work in the area of prognosis systematic reviews. Because of methodological shortcomings in the primary and review literature, there remains uncertainty about reliability of conclusions regarding prognostic factors for low back pain.