ABSTRACT
Healthcare decision-making needs to be informed by high quality and timely research evidence. The randomized controlled trial has long been considered the gold standard in the hierarchy of evidence. Trials involving sufficient numbers of participants are essential to distinguish reliably between the effects of healthcare interventions and the effects of bias or chance. The synthesis of the results of these trials in systematic reviews can provide reliable evidence about the effects of these interventions. The Cochrane Collaboration, an international organization dedicated to improving healthcare through the preparation of systematic reviews, has focused on the systematic electronic searching of Medline and EMBASE and the systematic hand searching of over 2000 general and specialized healthcare journals for reports of randomized controlled trials. This involves reading each document in a journal to decide if a report is a randomized trial, according to Cochrane eligibility criteria [1]. The efforts of the many volunteers working within the Cochrane Collaboration have added a substantial number of previously buried reports of randomized controlled trials to the Cochrane Central Register of Controlled Trials [CENTRAL] published in The Cochrane Library. Some of these reports of trials may have been buried as a result of inconsistencies in indexing [indexing bias], a lack of cover-to-cover indexing, or because they have been published in journals not indexed in the major healthcare databases such as Medline and EMBASE [database bias] or in journals published in languages other than English [language bias]. A good example of language bias was provided in a study of 68 Spanish general medicine journals, which found that only six were indexed in Medline [2]. The Bahrain Branch of the UK Cochrane Centre is contributing to efforts to minimize bias through a comprehensive handsearching of journals published in the Arab world