The Effect of English-Language Restriction on Systematic Review-Based Meta-Analyses: A Systematic Review of Empirical Studies

Abstract

<jats:p><jats:bold>Objectives:</jats:bold>The English language is generally perceived to be the universal language of science. However, the exclusive reliance on English-language studies may not represent all of the evidence. Excluding languages other than English (LOE) may introduce a language bias and lead to erroneous conclusions.</jats:p><jats:p><jats:bold>Study Design and Setting:</jats:bold>We conducted a comprehensive literature search using bibliographic databases and grey literature sources. Studies were eligible for inclusion if they measured the effect of excluding randomized controlled trials (RCTs) reported in LOE from systematic review-based meta-analyses (SR/MA) for one or more outcomes.</jats:p><jats:p><jats:bold>Results:</jats:bold>None of the included studies found major differences between summary treatment effects in English-language restricted meta-analyses and LOE-inclusive meta-analyses. Findings differed about the methodological and reporting quality of trials reported in LOE. The precision of pooled estimates improved with the inclusion of LOE trials.</jats:p><jats:p><jats:bold>Conclusions:</jats:bold>Overall, we found no evidence of a systematic bias from the use of language restrictions in systematic review-based meta-analyses in conventional medicine. Further research is needed to determine the impact of language restriction on systematic reviews in particular fields of medicine.</jats:p>

Quality of search strategies reported in systematic reviews published in stereotactic radiosurgery

“…Hand searching, which involves mainly the scrutiny of journal issues and reference lists of studies, is an important approach to increase the sensitivity of searches, especially when bibliographic database searches are not comprehensive. Although some evidence suggest that searching for documents published in English alone does not affect the size of treatment effect estimates, 11,12 this assumption may not be representative of all medical fields. Systematic review authors should thus search for publications Grey literature searched 0 (0) 1 (6) 11 (18) 12 (14) Hand search performed 0 (0) 1 (6) 6 (10) 7 (8) Search performed in duplicate 0 (0) 1 (6) 1 (2) 2 (2) Language restriction 0 (0) 0 (0) 7 (12) 7 (8) Contact with authors 0 (0) 1 (6) 2 (3) 3 (4) Interface reported 2 (29) 14 (78) 43 (72) 59 (69) Data are presented as number (percentage) unless otherwise stated.…”

Effect of high-flow nasal cannula oxygen therapy in adults with acute hypoxemic respiratory failure: a meta-analysis of randomized controlled trials

“…In addition, we restricted our literature search to trials published in English or Chinese. Although a systematic review found that English-language restriction did not introduce a language bias, 41 we conducted a comprehensive literature search including grey literature sources to minimize systematic bias.…”

Effectiveness of implementation strategies for clinical guidelines to community pharmacy: A systematic review

“…The decision to remove articles not written in English was based on resource limitations. There is evidence to suggest this was unlikely to introduce systematic bias into this review [32]. Articles were then screened for eligibility based on the previously devised PICO (participants, interventions, comparators, outcomes) framework [33].…”