An alternative screening approach for Google Search identifies an accurate and manageable number of results for a systematic review (case study)

Background A challenge when using Google Search to identify studies for a systematic review is managing the high number of results, which can number in the hundreds of thousands or even more. Studies and guidance on web searching suggest limiting the screening process, e.g. to the first 100 results. Objectives Our objective in this case study is to demonstrate an alternative approach to screening the results retrieved by Google Search which is based on our experience that the viewable number of results is often far fewer than the estimated number calculated by the search engine. Methods We screened the results of three searches of Google Search using our approach, which involves increasing the number of results displayed per page from 10 to the maximum of 100. We then calculated the viewable number of results and compared this with the estimated number. Results The mean of the estimated number of results for the three searches was 569,454,000. The mean of the viewable number results was 463 (0.00008% of the mean of the estimated number of results). Conclusion Our findings challenge the commonly reported view that the number of results retrieved when using Google Search is too high to screen in full.