Review Article
Systematic reviews of low back pain prognosis had variable methods and results—guidance for future prognosis reviews

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Abstract

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.

Introduction

Prognosis research can help clinicians educate patients and can be used to target specific interventions to modify prognostic factors. In many topic areas, increasing numbers of primary studies and systematic reviews of prognosis are being published [1]. Systematic reviews are literature reviews that use systematic identification, appraisal, and synthesis according to predefined methods [2]. However, there is limited guidance available to conduct systematic reviews of prognosis. Although basic principles used to reduce bias and random error are similar to those used for intervention reviews, there are several challenges unique to prognosis: lack of clarity in indexing of these studies for bibliographic searches; low quality of primary studies; poor reporting; differences in which prognostic factors were assessed and how they were defined; and difficulties in combining results across different research designs, analyses, and presentations [3].

In the field of low back pain, primary studies have presented inconsistent conclusions regarding important prognostic factors. A number of systematic reviews have been conducted that have attempted to synthesize the evidence on important prognostic factors for low back pain. However, they have often reached inconsistent conclusions, making this literature difficult to interpret. The objectives in our “review of reviews” are to systematically identify published systematic reviews of low back pain prognosis, and comprehensively describe and synthesize their methods, results, and conclusions. We will explore the potential impact of prognosis systematic review methods across sufficiently similar review questions.

Section snippets

Literature search and study selection

We searched the electronic databases MEDLINE, EMBASE, and CINAHL (up to June 2007) using a comprehensive strategy for prognosis studies [3], low back pain [4], and broad search terms for systematic reviews [1]. The complete search strategy is available (Appendix A; available on the journal's website at www.jclinepi.com). We screened references of existing systematic reviews, and the Institute for Work & Health's institutional database. We selected systematic reviews of nonspecific low back pain

Review selection

We identified 357 independent citations in our electronic search. This was supplemented with 29 additional citations (Fig. 1). We excluded two potentially relevant reviews published in German [7], [8], and one report that included systematic reviews [9]. Seventeen systematic reviews of low back pain prognosis, published between 2000 and 2006, were included [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26].

Review characteristics

The reviews ranged in quality, with

Discussion

We conducted a systematic review of 17 low back pain prognosis reviews. We observed important differences in the systematic review methods, and in the prognosis studies that each review included. We found only a small number of prognostic factors to be consistently associated with disability in acute/subacute low back pain. Our study highlights areas for further research and guidelines to improve the conduct and reporting of prognosis systematic reviews [31]. We identified issues and make

Acknowledgments

The authors thank Dr. George Tomlinson for comments on earlier versions of this article, Victoria Pennick for helping with editing and comments on earlier drafts, Dr. Mana Rezai for helping with the broad literature review screen and selection, Emma Irvin for helping with literature searches, and Quenby Mahood for helping with literature retrieval.

Funding: Dr. Jill Hayden's salary is partially funded by a research infrastructure grant from the Ontario Workplace Safety and Insurance Board, and

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