Implications for applications of FebriDx
What can be said about the utility of FebriDx by comparison with other POCTs given the limited available data? Preliminary judgements are possible depending on the [i] timing and location of testing; and [ii] the broader epidemiological context.
FebriDx offers greatest value early in the clinical course, given the absence of reliable antigen POCTs and scarcity of molecular POCTs. However, reported sensitivity ranges for COVID and non-COVID patients in healthcare settings are wide (5,6,13–16). The test should therefore be positioned within a diagnostic algorithm, alongside other clinical and radiological markers, to optimise performance. FebriDx may have a role in triage in the community where access to advanced diagnostics is limited, but there are no performance data for the test in this context, and only a handful of studies evaluate any SARS-CoV2 POCTs in the community (2).
Secondly, surrogate tests such as FebriDx will likely only have value around the peak of the epidemic curve, in a situation where widespread community transmission is probable. Here, a positive result in a patient with an ILI could be interpreted as indicative of COVID-19 pending laboratory confirmation. Discriminatory power will likely decline during the autumn and winter months where other viral diagnoses are equally or more likely. Here, the clinical and social cost of imposing infection control measures such as isolation on the basis of a presumptive diagnosis alone, may become unjustifiable.