Objective: To compare the quality of systematic reviews reported in English and in languages other than English, and to determine whether there are differences between conventional medicine (CM) and complementary and alternative medicine (CAM) reports.
Study design and setting: We used the Oxman and Guyatt (OG) scale to assess the quality of reporting in 130 systematic reviews: 50 were language-restricted, 32 were language-inclusive but only English-language (EL) trials contained (inclusive-EL), and 48 were language-inclusive and included trials published in languages other than English (inclusive-LOE). Of the 130 reviews, 105 addressed CM interventions and 25 addressed CAM interventions.
Results: Comparison of the systematic reviews showed that the quality of reporting and reporting characteristics are not affected by inclusion or exclusion of LOE; however, the quality of reporting of systematic reviews involving CAM interventions is higher than that of reviews focusing on CM interventions.
Conclusion: Informal comparison of the OG scale with the data collected on quality assessments showed that the OG scale performs well overall but may not identify important differences in comprehensiveness of the search strategy and avoidance of bias in study selection. Further research is required to determine the best methods for assessing quality of systematic reviews and whether the effect of language restrictions is dependent on the type of intervention (CM or CAM).