Appraisal of: Robinson KA, Dunn AG, Tsafnaf G, Glasziou P. Citation networks of related trials are often disconnected: implications for bidirectional citation searches. J Clin Epidemiol. 2014;67(7): 793-799.

Reviewer(s): 
Short description: 

The authors sought to determine the connectedness of citation networks of RCTs by examining direct (referenced trials) and indirect (through references of referenced trials, etc) citation of trials to one another. 259 meta-analyses including 2,413 RCTs were used to create citation networks of RCTs addressing the same clinical questions.

For 46% (118 of 259) of networks, the RCTs formed a single connected citation group - one island. For the other 54% of networks, where at least one RCT group was not cited by others, 39% had two citation islands and 4% (10 of 257) had 10 or more islands.

Conclusion: Available evidence to answer a clinical question may be identified by using network citations created with a small initial corpus of eligible trials. However, the number of islands means that citation networks cannot be relied on for evidence retrieval.

Limitations stated by the author(s): 

The authors stated some limitations.

They used Web of Science to identify the Meta-Analysis and the RCTs included in those Meta-Analysis. Some networks are thus not complete as one or more of the RCTs from the MA are not included in their data set. Given the relatively small number of RCTs missing per network, it is not likely that these missing RCTs would substantively change the results.

Another limitation is that a trial could have cited systematic reviews rather than individual prior trials. They did not check this as other studies have suggested few trials cite up-to-date systematic reviews.

Limitations stated by the reviewer(s): 
The study is of high quality, one limitation might be, that only trials were included in the analysis. However, the results might be better when all references from the reference lists were analysed.
Study Type: 
Single study