Background There is lack of evidence for specific treatment interventions for patients with non-specific chronic low back pain (NSCLBP) despite the substantial amount of randomised controlled clinical trials evaluating treatment outcome for this disorder.

Hypothesis It has been hypothesised that this vacuum of evidence is caused by the lack of subclassification of the heterogeneous population of patients with chronic low back pain for outcome research.

Study design A systematic review.

Methods A systematic review with a meta-analysis was undertaken to determine the integration of subclassification strategies with matched interventions in randomised controlled clinical trials evaluating manual therapy treatment and exercise therapy for NSCLBP. A structured search for relevant studies in Embase, Cinahl, Medline, PEDro and the Cochrane Trials Register database, followed by hand searching all relevant studies in English up to December 2008.

Results Only 5 of 68 studies (7.4%) subclassified patients beyond applying general inclusion and exclusion criteria. In the few studies where classification and matched interventions have been used, our meta-analysis showed a statistical difference in favour of the classification-based intervention for reductions in pain (p=0.004) and disability (p=0.0005), both for short-term and long-term reduction in pain (p=0.001). Effect sizes ranged from moderate (0.43) for short term to minimal (0.14) for long term.

Conclusion A better integration of subclassification strategies in NSCLBP outcome research is needed. We propose the development of explicit recommendations for the use of subclassification strategies and evaluation of targeted interventions in future research evaluating NSCLBP.