To the Editor The authors are to be congratulated for conducting this important but challenging systematic review.1 However, while accepting its degree of complexity, we are at variance with the confidence expressed by the authors in the strengths of their study, including a thorough search of the literature and exclusion of lower-quality reports assessed using the Jadad score. A thorough literature search is a key requirement of a high-quality systematic review and, as the authors confirm, should show all the evidence available at the time of the study.1 Although their search appeared comprehensive, language of publication was clearly a restriction; ie, only studies in English, Spanish, and Portuguese were included. The exclusion of studies based on language of publication is a significant source of bias, which has been well documented, and in this review, the language restriction excludes studies published in the German language.2,3 Hand searching of pre-1987 issues of Mykosen would have identified additional eligible trials, most of which are written in German, and which, based on the flowchart included as the first figure in the article, would have represented a not insignificant percentage of the total number of included trials. The review excluded a number of German studies equivalent to the number of Spanish and Portuguese studies that were included, clearly illustrating the impact of language bias and the not inconsequential gap in the evidence included in this systematic review. In addition, the limitations of numerical quality scores, eg, the Jadad Scale, are well documented and widely acknowledged.4,5 The Cochrane Handbook for Systematic Reviews of Interventions, referred to by the authors, explicitly discourages the use of numerical quality scores in view of their increased emphasis on the quality of the reporting rather than the conduct of trials.1 The authors claim a degree of certainty about the methodologic quality of their included studies and state that the “absence of information about the allocation should not have affected the confidence of the results.”1(p343) However, inadequate reporting of key quality items, ie, sequence generation and concealment, does somewhat limit our degree of confidence in judgments of low as opposed to unclear risk of bias for these domains. The Cochrane risk-of-bias tool was used by the authors to assess “evidence generated…not being considered as conforming to the eligibility criteria”1(p342) and “the risk of bias in the included studies,”1(p342) but these key assessments and corresponding judgements are conspicuously absent in the report. Although we are in broad agreement that the conclusions of this report reflect the findings, we express concern with the methods used to reach these conclusions, which are not reflective of a robust and comprehensive process used to synthesize all the available evidence for this clinical topic. Back to top Article Information Corresponding Author: Zbys Fedorowicz, MSc, DPH, UK Cochrane Centre (Bahrain Branch), The Cochrane Collaboration, Box 25438, Awali, Bahrain (firstname.lastname@example.org). Conflict of Interest Disclosures: No specific financial conflicts were reported. However, both authors are currently conducting a Cochrane Review on topical antifungal treatments for tinea cruris and tinea corporis. Disclaimer: Although both authors are members of The Cochrane Collaboration, the views expressed in this letter are not necessarily the views or the official policy of The Cochrane Collaboration. References 1. Rotta I, Ziegelmann PK, Otuki MF, Riveros BS, Bernardo NLMC, Correr CJ. Efficacy of topical antifungals in the treatment of dermatophytosis: a mixed-treatment comparison meta-analysis involving 14 treatments. JAMA Dermatol. 2013;149(3):341-349.PubMedGoogle ScholarCrossref 2. Türp JC, Schulte JM, Antes G. Nearly half of dental randomized controlled trials published in German are not included in Medline. Eur J Oral Sci. 2002;110(6):405-411.PubMedGoogle ScholarCrossref 3. Guyatt GH, Oxman AD, Montori V, et al. GRADE guidelines: 5, rating the quality of evidence—publication bias. J Clin Epidemiol. 2011;64(12):1277-1282.PubMedGoogle ScholarCrossref 4. Olivo SA, Macedo LG, Gadotti IC, Fuentes J, Stanton T, Magee DJ. Scales to assess the quality of randomized controlled trials: a systematic review. Phys Ther. 2008;88(2):156-175.PubMedGoogle ScholarCrossref 5. Herbison P, Hay-Smith J, Gillespie WJ. Adjustment of meta-analyses on the basis of quality scores should be abandoned. J Clin Epidemiol. 2006;59(12):1249-1256.PubMedGoogle ScholarCrossref
JAMA Dermatology – American Medical Association
Published: Oct 1, 2013
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