Evaluation of triage tests when existing test capacity is constrained: application to rapid diagnostic testing in COVID-19

Abstract

Objectives: A triage test is used to determine which patients will undergo an existing or ‘reference’ test. This paper explores the potential value of triage tests before reference tests when capacity of the reference test is constrained.

Methods: We developed a simple model with inputs: prevalence, sensitivity, specificity and reference test capacity. We included a case study of rapid diagnostic tests for recombinant SARS-CoV- 2antigens used as triage tests before a reference polymerase chain reaction test. Performance data is taken from evaluation by the Foundation for Innovative New Diagnostics.

Results: When reference test capacity is constrained, the use of a triage test leads to a relative expansion of the population tested and cases identified, both are higher with a high specificity test. When reference test capacity is not constrained, the introduction of a triage test can be assessed using a standard cost-consequence or cost-utility framework balancing the benefit of the reduction in the number of reference tests required against the disbenefit of missed cases. In this case a test with high specificity leads to the greatest reduction in the number of reference tests required and to the greatest number of missed cases. In the constrained case, the advantage of a triage testing strategy in terms of population covered and cases identified reduces as prevalence increases. In the unconstrained case, the reduction in reference tests required is reduced and cases missed increase as prevalence rises.

Conclusion: When availability of reference test is constrained, tests added in a triage position do not need high levels of accuracy to increase number of cases diagnosed. This has implications in many disease areas including COVID-19.

Rights

http://creativecommons.org/licenses/by-nc-nd/4.0/

Cite as

Downloadable citations

Identifiers

DOI

http://dx.doi.org/10.1177/0272989X211014114

Repository URI

http://eprints.gla.ac.uk/238555/