Background: Searching various databases is an exhausting job for researchers. Different databases require different terminologies and different filters and multiple databases need to be searched for ensuring comprehension and avoiding bias. The search strategies formulated are therefore long and involve great expertise. Using search filters provided by the databases is therefore an aid to decrease the load. There are available search terms for searching for randomized controlled trials, but no such standardized strategy exists for searching for observational studies.
Objectives: Comparison of search outputs with or without using the search filters in searches involving observational studies.
Methods: We illustrate the use of search filters and searching without the use of specific filters through an example of a systematic review of observational studies. The databases searched were Pubmed, Embase and MEDLINE via Ovid SP. Two reviewers searched the databases independently, one used the search filters provided by the database and the second reviewer did not use the specific filters, but instead used the specific search terms for the observational studies for electronic searching of the databases. The other blinded reviewers then compared and screened the results.
Results: Use of specific search filters significantly decreased the total number of hits from 16323 records to 6423 records and did away with most of the irrelevant results, but missed out on 5% of the included studies.
Conclusions: The specific search filters reduce the workload, but need to be used with caution as some of the important records may be missing.
Acknowledgements: This study was supported by WHO, Geneva & ICMR, New Delhi