Review Article| Volume 61, ISSUE 3, P209-231, March 2008

Methodological quality and homogeneity influenced agreement between randomized trials and nonrandomized studies of the same intervention for back pain

  • Andrea D. Furlan
    Corresponding author. Tel.: 1-416-927-2027; fax: 1-416-927-4167.
    Institute for Work & Health, Toronto, ON, Canada M5G 2E9

    University of Toronto, Department of Health Policy, Management and Evaluation, Canada
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  • George Tomlinson
    University of Toronto, Department of Health Policy, Management and Evaluation, Canada

    Department of Medicine at University of Toronto, Toronto General Research Institute, Canada
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  • Alejandro (Alex) R. Jadad
    University of Toronto, Department of Health Policy, Management and Evaluation, Canada

    Centre for Global eHealth Innovation, Canada

    Rose Family Chair in Supportive Care, Canada
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  • Claire Bombardier
    Institute for Work & Health, Toronto, ON, Canada M5G 2E9

    University of Toronto, Department of Health Policy, Management and Evaluation, Canada

    Department of Medicine at University of Toronto, Toronto General Research Institute, Canada

    Division of Rheumatology, University of Toronto, Canada

    Mount Sinai Hospital, Toronto, Canada
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      To determine the influence of methodological quality and homogeneity on the agreement between pairs of randomized trials (RCTs) and nonrandomized studies (NRSs) of the same interventions for low-back problems. Homogeneity was assessed regarding settings, population, interventions, and outcomes.

      Study Design and Setting

      We searched Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE up to May 2005 for matching pairs of NRS and RCT. Analyses were done using correlation, linear and logistic regression.


      Forty-eight matched pairs were included with no significant overall correlation between effect sizes (r=0.09). There was a trend showing more agreement among the 22 pairs with higher methodological quality (r=0.33). The correlation among the 20 very homogeneous pairs was 0.59, and among the 28 heterogeneous pairs was −0.09. The agreement of authors' recommendations was influenced by the pair's homogeneity (odds ratio [OR]=2.78, 95% CI=1.44–5.37) rather than by methodological quality of the NRS (OR=0.93, 95% CI=0.67–1.29) or the RCT (OR=1.03, 95% CI=0.73–1.45).


      Pairs of low-quality studies disagreed more than pairs where at least one study was of high quality. However, pairs with similar settings, population, interventions, and outcomes showed higher agreement than pairs that were not as homogeneous.


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