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.