Abstract
The Cochrane COVID-19 Study Register (CCSR) is a public, continually updated database of COVID-19 study references. The aim of this study-based register is to support rapid and living evidence synthesis, including an evidence ecosystem of COVID-19 research (CEOsys). In November and December 2020, we conducted an evaluation of the CCSR for CEOsys, measured its performance and identified areas for improvement. For the evaluation we generated a purposive sample of 286 studies from 20 reviews to calculate the CCSR's comprehensiveness (sensitivity), accuracy (correctly classified and linked studies) and currency (time to publish and process references). Our sample showed that the CCSR had an overall comprehensiveness of 77.2%, with the highest coverage for interventional studies (94.4%). The study register had 100% coverage for trial registry records, 86.5% for journal articles and 52.4% for preprints. A total of 98.3% of references were correctly classified with regard to study type, and 93.4% with regard to study aim. A total of 89% of studies were correctly linked. A total of 81.4% of references were published to the register in under 30 days, with 0.5 day (median) for trial registry records, 2 days for journal articles and 56 days for preprints. The CCSR had high comprehensiveness, accurate study classifications and short publishing times for journal articles and trial registry records in the sample. We identified that coverage and publishing time for preprints needed improvement. Finally, the evaluation illustrated the value of a study-based register for identifying additional study references for analysis in evidence synthesis.