Use of the FebriDx point-of-care assay as part of a triage algorithm for medical admissions with possible COVID-19

Houston, H.; Gupta-Wright, A.; Deas, G.; Naik, S.; Shah, K.; Patel, S.; Dottori, M. G.; Tay, M.; Filson, S.; Biggin-Lamming, J.; Ross, J.; Vaughan, N.; Vaid, N.; Gopal Rao, G.; Amin, A.; John, L.

Background: Patients admitted to hospital with COVID-19 must be rapidly identified and isolated to prevent nosocomial transmission. However, isolation facilities are often limited, and SARS-CoV-2 RT-PCR results are too slow to inform emergency department triage. We evaluated a pragmatic triage algorithm to isolate patients with suspected COVID-19 using simple clinical criteria and the FebriDx assay. Methods: All medical admissions in a large UK hospital were triaged as likely, possible or unlikely COVID-19 based on clinical criteria. Patients triaged as possible COVID-19 underwent FebriDx lateral flow assay on capillary blood, and those who tested MxA positive were isolated. We evaluated the accuracy of the algorithm and the FebriDx assay compared to SARS-CoV-2 RT-PCR from nasopharyngeal swabs as the reference standard. Results: Between 10th August 2020 and 4th November 2020, 136/3,443 medical admissions (4.0%) were diagnosed with RT-PCR confirmed COVID-19. Prevalence of COVID-19 was 45.7% (80/175) in those triaged as likely, 4.1% (50/1,225) in possible and 6/2,033 (0.3%) in unlikely COVID-19. Compared to SARS-CoV-2 RT-PCR, clinical triage had sensitivity of 95.6% (130/136) and specificity of 61.5% (2027/3297), whilst the triage algorithm including FebriDx had sensitivity of 92.6% (126/136) and specificity of 86.4% (2849/3297). The triage algorithm reduced the need for 2,859 patients to be admitted to isolation rooms. The patients missed by the algorithm had mild or asymptomatic COVID-19. Conclusions: A simple triage algorithm including FebriDx assay had good sensitivity and is a useful rule-out for COVID-19. The algorithm is useful for managing medical admissions from the emergency department.