标题：Efficiency and contribution of strategies for finding randomized controlled trials: a case study from a systematic review on therapeutic interventions of chronic depression
摘要：Background . Identifying all existing evidence is a crucial aspect in conducting systematic reviews. Since the retrieval of electronic database searches alone is limited, guidelines recommend the use of addi- tional search strategies. The aim of this investigation was to assess the efficiency and contribution of additional search strategies for identifying randomized controlled trials in conducting a systematic review on interventions after performing a sensitive electronic database search. Design and Methods . Seven electronic databases, 3 journals and 11 systematic reviews were searched. All first authors of the included studies were contacted; citation tracking and a search in clinical trial registers were performed. A priori defined evaluation criteria were calculated for each search strategy. Results . A total of 358 full-text articles were identified; 50 studies were included in the systematic review, wherefrom 84.0% (42) were acquired by the sensitive electronic database search and 16.0% (8) through additional search strategies. Screening reference lists of related systematic reviews was the most beneficial additional search strategy, with an efficiency of 31.3% (5) and a contribution of 10.0% (5/50), whereas hand-searching and author contacts contributed two and one additional studies, respectively. Citation tracking and searching clinical trial registers did not lead to any further inclusion of primary studies. Conclusions . Based on our findings, hand-searching contents of relevant journals and screening reference lists of related systematic reviews may be helpful additional strategies to identify an extensive body of evidence. In case of limited resources, a sensitive electronic database search may constitute an appropriate alternative for identifying relevant trials.
