Appraisal of: Westphal A, Kriston L, Holzel LP, Harter M, von Wolff A. Efficiency and contribution of strategies for finding randomized controlled trials: a case study from a systematic review on therapeutic interventions of chronic depression. J Public H

Short description: 

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 the efficacy of psychotherapeutic, pharmacological and combined interventions in the treatment of chronic depression after performing a sensitive electronic database search.

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.

50 studies were included in the systematic review, wherefrom 94% were acquired by the sensitive electronic database search and 16% through additional search strategies. Screening reference lists of related systematic reviews was the most beneficial additional search strategy with a contribution of 5 additional references. Citation tracking did not lead to any further inclusion of primary studies. 

Limitations stated by the author(s): 

Since our investigation is a single case study of a systematic review on interventions of chronic depression, the generalizability of our findings to other research topics may be limited. Above, the presented search strategies were applied in the research area of therapies that focus on chronic depression so that we could draw on a relatively large number of existing systematic reviews, 11 in total, that were rewarding for our analysis. Accordingly, in areas less researched, this beneficial additional search strategy cannot be applied.23 Furthermore, we conducted a sensitive electronic database search which might have limited the gain of additional search strategies. In contrast, the use of only one database (e.g., MEDLINE) and a more restrictive search could have resulted in a significantly larger benefit through additional search strategies.

Another possible limitation of our findings may consist in the choice of the journals that were searched for relevant content since this selection may have influenced the number of identified studies through this strategy as well as the relative efficiency of other strategies conducted subsequently.

In addition, we did not consult an expert, e.g. a librarian, for designing the terms for the electronic database search, so we may have missed a few studies. However, it should be noted that several of the authors have extensive training and experience in performing systematic reviews and searches within them.

Above, the contribution of any additional search strategy strongly depends on the order of its application. In this case contents of relevant journals were searched at first. As we did not investigate any alternative sequence of additional search strategies and thus did not calculate the overlap between the applied additional search strategies, the generalizability of our findings may be limited. Although we applied many additional search strategies, the search for grey literature was limited. As the inclusion of unpublished trials in systematic reviews is a controversially discussed issue that is capable of both reducing and introducing bias, we decided not to search for additional unpublished trials.

Limitations stated by the reviewer(s): 
It is not stated which references and how many were used for citation tracking and screening reference lists of systematic reviews.
Study Type: 
Single study