Are fast test results preferable to high test sensitivity in contact-tracing strategies?

Abstract

Across the world, countries are fighting to reduce the spread of COVID-19. The backbone of the response is a test-trace-isolate strategy, where suspected infected get tested and isolated and possible secondary cases get traced, tested and isolated. Because more accurate tests often take longer to analyze, and the benefits of contact tracing are strengthened by rapid diagnosis, there exists a trade-off in test sensitivity and test waiting time in test-trace-isolate strategies. Here we ask: How many false negatives can be tolerated in a rapid test so that it reduces transmission better than a slower, more accurate test? How does this change with contact tracing efficiency and test waiting time? We find that a rapid, less sensitive test performs best for many test-parameter choices and that this is true even for modest contact tracing efficiency. For COVID-19-like viral parameters, a test with 40% false negatives and immediate result might reduce transmission as well as a test with no false negatives and a 3-day waiting time. Our analysis suggests employing rapid tests to reduce test waiting times as a viable strategy to reduce transmission when testing infrastructure is under stress.

Accuracy of anterior nasal swab rapid antigen tests compared with RT‐PCR for massive SARS‐CoV‐2 screening in low prevalence population

“…The Ag test sensitivity shall be interpreted in light of the low prevalence in the investigated population, as low prevalence in general challenges sensitivity of diagnostics test [ 13 ]. Furthermore, the lower sensitivity of the Ag test, as described in the introduction, does not affect the important value of the Ag test in screening as long as frequency of the testing is high [ 4 , 5 , 6 ]. Recommendations suggest that the rapid Ag test is useful as an epidemiologic and scalable screening and results in a valid COVID passport when testing is frequent, that is, every third day [ 4 , 5 , 6 ], thus, the Ag test even with a lower sensitivity is an acceptable screening tool taking into account the minimal invasive method of collecting the sample for analysis, the fast result time, and the lower costs.…”

“…Furthermore, the lower sensitivity of the Ag test, as described in the introduction, does not affect the important value of the Ag test in screening as long as frequency of the testing is high [ 4 , 5 , 6 ]. Recommendations suggest that the rapid Ag test is useful as an epidemiologic and scalable screening and results in a valid COVID passport when testing is frequent, that is, every third day [ 4 , 5 , 6 ], thus, the Ag test even with a lower sensitivity is an acceptable screening tool taking into account the minimal invasive method of collecting the sample for analysis, the fast result time, and the lower costs. It has further been shown that individuals with a lower Ct value, and thus a high viral load, have been associated with a higher transmissibility of SARS‐CoV‐2.…”

“…It is noteworthy that we did not find any false positive test and the Ag test thus did not lead to unnecessary isolation and quarantine. This might be a problem with infrequent testing with a more sensitive test as individuals in the recovery period, who have a virus load below the infectious threshold, can test positive even though they are not at risk of infecting [ 4 , 5 ]. This has an important impact for the tested individuals personally and on a larger scale for the society and economic situation in general.…”

“…Especially the latter can potentially lead to a faster containment of infection in the society. Even though the Ag test has a lower sensitivity compared to the RT‐PCR test it has been shown that optimal screening depends highly on the frequency and speed of testing and is only marginally improved by high sensitivity [ 4 , 5 , 6 ].…”

A Scoping Review of Supply Chain Management Systems for Point of Care Diagnostic Services: Optimising COVID-19 Testing Capacity in Resource-Limited Settings

“…The primary goal of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) testing is to reduce the spread of coronavirus disease 2019 (COVID-19) [ 1 , 2 ]. Due to the highly infectious nature of SARS-CoV-2, there is an urgent need for a fast turnaround of results to institute preventative measures such as the isolation of confirmed cases and contact tracing [ 1 , 3 ]. Currently, reverse transcription polymerase chain reaction (RT-PCR) tests are the gold standard for diagnosing COVID-19 [ 4 , 5 , 6 ].…”