Real-World Diagnostic Accuracy of a Host Response Point-of-Care Test in Hospitalised Patients with Suspected COVID-19

Abstract

Background: The management of the COVID-19 pandemic is hampered by long delays associated with centralised laboratory PCR testing. In hospitals this leads to poor patient flow and nosocomial transmission and so rapid, accurate diagnostic tests are urgently required. The FebriDx is a CE-marked point-of-care test (POCT) that detects host response proteins in finger prick blood within 10 minutes to distinguish viral from bacterial respiratory infection, but its accuracy for the detection of COVID-19 is unknown.

Methods: We performed a real-world diagnostic accuracy study of the FebriDx in hospitalised patients, nested within a larger study assessing molecular diagnostics for COVID-19. Measures of diagnostic accuracy were calculated based on FebriDx results compared to the reference standard of PCR, and stratified based on duration of symptoms. A multivariable predictive model including FebriDx, age, sex, symptoms and signs was also developed and underwent internal validation. The parent study is registered, number ISRCTN17197293 and is ongoing.

Findings: 266 hospitalised adults with suspected COVID-19 were enrolled. FebriDx was performed on 251 patients and gave a valid result in 248. 118 of 248 (48%) were PCR positive for COVID-19. Sensitivity of FebriDx for the identification of COVID-19 was 93% (110/118; 95% CI 87 to 97%) and specificity was 86% (112/130; 95%CI 79 to 92%). Positive and negative likelihood ratios were 6.73 (95%CI 4.37 to 10.37) and 0.08 (95%CI 0.04 to 0.15) respectively. In the multivariate model diagnosis of COVID-19 was not significantly influenced by age or clinical symptoms and signs including fever, and FebriDx accuracy was not improved by restricting testing to those with duration of symptoms of less than seven days.

Interpretation: FebriDX has high diagnostic accuracy for the identification of COVID-19 in hospitalised adults and could be used as a front door triage tool, representing a cheap and widely available solution to delayed diagnosis.

Trial Registration: This study was prospectively registered with the ISRCTN14966673 on the 18th March 2020.

Funding Statement: This study was funded by University Hospital Southampton Foundation NHS trust.

Declaration of Interests: All other authors declare that they have no conflicts of interests relating to this work.

Ethics Approval Statement: The study was approved by the South Central - Hampshire A Research Ethics Committee: REC reference 20/SC/0138, on the 16th March 2020.

Keywords: COVID-19; diagnosis; accuracy; point-of-care; host response; hospital