Background <p>Ebolavirus and related filoviruses are feared pathogens due to high mortality rates, and cases are confirmed using reverse transcription-polymerase chain reaction (RT-PCR) testing. Compared to rapid diagnostic testing (RDT), RT-PCR has higher accuracy but longer turnaround time and lower testing rate. RDTs’ accuracy for Ebola does not meet the World Health Organization’s (WHO) target product profile (TPP). This TPP, however, excludes trade-offs between accuracy, time-to-isolation (the time from getting tested to getting hospitalized and isolated), and accessibility. This research aims to guide diagnostic test development and use by identifying trade-offs in accuracy, time-to-isolation, and accessibility that enable impactful outbreak response.</p> Methods <p>A mathematical compartmental model was calibrated to the 2014–2016 Sierra Leone EBOV epidemic, including test accuracy, accessibility, and time-to-isolation parameters. These parameters were varied to evaluate their impact on total epidemic size in different in isolation and in combination.</p> Results <p>Reductions in EBOV test sensitivity or specificity alone will increase the expected number of cases from 11.7 to 223%, while any decrease in time-to-isolation alone (due to a more rapid test result) or increase in testing rate alone would decrease the expected number of cases by 47.7–87.7%. When combining the three factors together, the benefits associated with an RDT would outweigh the harms, with a combined net reduction of mean cases between 71.6 and 92.3%.</p> Conclusions <p>When coupled with a more rapid turnaround time and increase in test access, the use of a lower performance test can result in significantly reduced epidemic size compared to relying on PCR alone in an EBOV outbreak in a resource-limited setting.</p>