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[Critical analysis of a systematic review of the literature and a meta-analysis on exercise therapy and chronic low back pain].

OBJECTIVES
To determine wether the type of quality assessment scale used for evaluating the role of the physical training in chronic low back pain affects the conclusions of meta-analytic studies.


DESIGN AND SETTING
Analysis of 20 trials assessing exercise therapy in chronic low back pain using 16 different scales to identify high-quality trials. Correlations between the scale scores were assessed using the Spearmans rank correlation coefficient. Inter-reader reliability was assessed with the intraclass correlation coefficient (ICC) and with the Bland and Altman technique. For the quality assessment scales allowing the classification in high quality or low quality trials, the degree of agreement between the two readers was calculated using the kappa coefficient.


RESULTS
The range of the Spearman rank correlation coefficients between the different quality scales was wide (from 0.94 to 0.49). The quality scales inter-reader reliability were heterogeneous, ICC ranging from 0.86 to 0.39. The Bland and Altman analysis showed that with two scales the differences were not centered and that with 3 scales there was a systematic effect (r=0.32, 0.41, and 0.50). Finally, inter-reader agreement was low most of the time, the K coefficient being less than or equal to 0.60 for 8 of the 12 quality scales tested.


CONCLUSIONS
Our data suggest that the use of summary scores to identify trials of high quality is problematic. Relevant methodological aspects should be assessed more specifically based on treatment strategies than on the own disease. A large reflexion on the elaboration and validation of specific quality scales is needed.