FebriDx host response point-of-care testing improves patient triage for coronavirus disease 2019 (COVID-19) in the emergency department

Use of the FebriDx® host-response point-of-care test may reduce antibiotic use for respiratory tract infections in primary care: a mixed-methods feasibility study

INTRODUCTION

FebriDx® is a CE-marked, single-use point-of-care test with markers for bacterial [C-reactive protein (CRP)] and viral [myxovirus resistance protein A (MxA)] infection, using finger-prick blood samples. Results are available after 10-12 min. We explored the usability and potential impact of FebriDx® in reducing antibiotic prescriptions for lower respiratory tract infection (LRTI) in primary care, and the feasibility of conducting a randomized controlled trial (RCT).

METHODS

Patients (aged ≥1 year) with LRTI deemed likely to receive antibiotic prescription were recruited at nine general practices and underwent FebriDx® testing. Data collection included FebriDx® results, antibiotic prescribing plan (before and after testing) and re-consultation rates. Staff completed System Usability Scale questionnaires.

RESULTS

From 31 January 2023 to 9 June 2023, 162 participants participated (median age 57 years), with a median symptom duration of 7 days (IQR 5-14). A valid FebriDx® result was obtained in 97% (157/162). Of 155 patients with available results, 103 (66%) had no detectable CRP or MxA, 28 (18%) had CRP only, 5 (3%) had MxA only, and 19 (12%) had both CRP and MxA. The clinicians' stated management plan was to prescribe antibiotics for 86% (134/155) before testing and 45% (69/155) after testing, meaning a 41% (95% CI: 31%, 51%) difference after testing, without evidence of increased re-consultation rates. Ease-of-use questionnaires showed 'good' user-friendliness.

CONCLUSIONS

Use of FebriDx® to guide antibiotic prescribing for LRTI in primary care was associated with a substantial reduction in prescribing intentions. These results support a fully powered RCT to confirm its impact and safety.

Emergency Department point-of-care antiviral host response testing is accurate during periods of multiple respiratory virus co-circulation

OBJECTIVES

FebriDx is a CE-marked, FDA-approved point-of-care test that detects the antiviral host response protein Myxovirus Resistance Protein A (MxA), in addition to C-reactive protein, using finger-prick blood. FebriDx MxA detection had a high negative predictive value for COVID-19 in symptomatic adults presenting to hospital in the first waves of the pandemic and was used subsequently as a 'rule out' triage tool in Emergency departments. The diagnostic accuracy of FebriDx MxA in the current context of co-circulation of influenza, SARS-CoV-2, and Respiratory Syncytial Virus (RSV), and in the era of COVID-19 vaccination, is unknown.

METHODS

We retrospectively evaluated the diagnostic performance of FebriDx MxA in adults with acute respiratory symptoms presenting to the Emergency Department (ED) of a large UK teaching hospital using Reverse Transcription Polymerase Chain Reaction (RT-PCR) as the reference standard (Cepheid Xpert Xpress SARS-CoV-2/Flu/RSV).

RESULTS

Between March 9th 2022 and March 8th 2023, 5426 patients had both FebriDx and RT-PCR testing with valid results. 999 (18.4%) of patients had influenza detected, 520 (9.6%) SARS-CoV-2, and 190 (3.5%) RSV. Negative Predictive Value (NPV) of MxA detection by FebriDx was 97.5% (96.9-98.0) for influenza, 97.1% (96.4-97.7) for SARS-CoV-2, 98.1% (97.5-98.6) for RSV, and 92.8% (91.8-93.7) for all viruses combined.

CONCLUSIONS

In symptomatic adults, FebriDx MxA had a high NPV for influenza and RSV, and retained a high NPV for SARS-CoV-2, in the context of virus co-circulation and widespread COVID-19 vaccination. FebriDx continues to be a useful 'rule out' triage tool in the ED and could potentially be scaled to provide a national triage solution for future viral pandemics.

Performance of the FebriDx Rapid Point-of-Care Test for Differentiating Bacterial and Viral Respiratory Tract Infections in Patients with a Suspected Respiratory Tract Infection in the Emergency Department

FebriDx is a rapid point-of-care test combining qualitative measurements of C-reactive protein (CRP) and Myxovirus Resistance Protein A (MxA) using a disposable test device to detect and differentiate acute bacterial from viral respiratory tract infections. The goal of this study was to investigate the diagnostic accuracy of FebriDx in patients with suspected respiratory tract infections in the emergency department (ED). This was an observational cohort study, performed in the ED of an academic hospital. Patients were included if they had a suspected infection. The primary outcome was the presence of a bacterial or viral infection, determined by clinical adjudication by an expert panel. The sensitivity, specificity, and positive and negative predictive value of FebriDx for the presence of bacterial versus non-bacterial infections, and viral versus non-viral infections were calculated. Between March 2019 and November 2020, 244 patients were included. A bacterial infection was present in 41%, viral infection was present in 24%, and 4% of the patients had both viral and bacterial pathogens. FebriDx demonstrated high sensitivity in the detection of bacterial infection (87%), high NPV (91%) to rule out bacterial infection, and high specificity (94%) for viral infection in patients with a suspected infection in the ED.

Negative predictive value of the FebriDx host response point-of-care test in patients presenting to a single Australian emergency department with suspected COVID-19: an observational diagnostic accuracy study

OBJECTIVES

To determine the negative predictive value (NPV) of the FebriDx point-of-care host response device in patients presenting with symptoms suggestive of COVID-19 infection in a mostly immunised Australian emergency department (ED) population during the late 2021 phase of the COVID-19 pandemic.

DESIGN

Observational diagnostic accuracy study comparing FebriDx point-of-care test to SARS-CoV-2 PCR.

SETTING

An ED in Melbourne, Australia, with 63 000 annual presentations in 2021.

PARTICIPANTS

Patients aged 16 and over who met the Victorian Department of Health case definition for suspected COVID-19 infection PCR testing. Patients meeting any of the following criteria were excluded: <16 years of age; acute respiratory symptom(s) with onset>14 days prior to testing; current immunosuppressive or interferon therapy; live immunisation within the last 30 days; fever lasting>7 days; antibiotic or antiviral use in the preceding 14 days; experience of major trauma, major surgical intervention or severe burns within the last 30 days.

PRIMARY AND SECONDARY OUTCOME MEASURES

COVID-19 PCR results (detected, not detected) and FebriDx results (bacterial positive, viral negative, viral positive).

RESULTS

94 participants were enrolled (female: 46; male: 48), 34% of participants (tested positive for COVID-19 according to PCR results, with a background incidence among all adult ED attenders of 2.5%. The sensitivity of FebriDx for detection of COVID-19 was 56% (95% CI 40% to 100%) and specificity was 92% (95% CI 84% to 100%). For the population tested, this resulted in an NPV of 80% (95% CI 71% to 100%) and a positive predictive value of 78% (95% CI 60% to 100%).

CONCLUSIONS

In the context of a population with low COVID-19 infection rates, an evolved variant of COVID-19 and a very high community COVID-19 vaccination rate, FebriDx demonstrated reduced sensitivity and NPV relative to results from earlier international tests. These contextual factors should be considered during any attempt to generalise the current results.

TRIAL REGISTRATION NUMBER

ACTRN12620001029987 (Australian Clinical Trials).

Combined RT-PCR and Host Response Point-of-Care Testing in Patients Hospitalised with Suspected COVID-19: A Prospective Diagnostic Accuracy Study

Introduction

RT-PCR has suboptimal sensitivity for the diagnosis of COVID-19. A composite reference standard comprising RT-PCR plus radiological and clinical features has been recommended for diagnostic accuracy studies. The FebriDx finger prick point-of-care test detects an antiviral host response protein (MxA) in 10 min. We evaluated the diagnostic accuracy of FebriDx and RT-PCR compared to a composite reference standard.

Methods

Adults presenting to hospital with suspected COVID-19 were tested by FebriDx and RT-PCR. A composite reference standard was used to classify patients as having COVID-19 based on RT-PCR positivity, or RT-PCR negativity with COVID-19 radiological findings or other clinical criteria. Measures of accuracy were calculated for MxA alone, RT-PCR alone, and both combined. This study is registered with the ISRCTN (ISRCTN14966673) and has completed.

Results

A total of 478 patients were tested, with valid results in 475. Of these 475 patients, 222 (46.7%) were classified as having COVID-19; 192 (40.4%) were RT-PCR positive, and 30 (6.3%) were RT-PCR negative and diagnosed on radiological/clinical criteria. Sensitivity of FebriDx MxA vs the composite reference standard was 186/222 (83.8%, 95% CI 78.3–88.4) and was similar to the sensitivity of RT-PCR (192/222 (86.5%, 95% CI 81.3–90.7), (difference of 2.7%, 95% CI − 3.9 to 9.3, p = 0.42). The sensitivity of combined FebriDx and RT-PCR was 208/222 (93.7%) which was superior to both RT-PCR alone (difference of 9.9, 95% CI 4.1–15.9; p = 0.001) and FebriDx MxA alone (difference of 7.2, 95% CI 1.6–12.9; p = 0.011).

Conclusion

Sensitivity of combined FebriDx and RT-PCR testing was superior to each alone for the detection of COVID-19 in hospital and may improve infection control and treatment decisions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-022-00646-4.

FebriDx for rapid screening of patients with suspected COVID-19 upon hospital admission: systematic literature review and meta-analysis

A systematic literature review and meta-analysis was undertaken of the lateral flow-based FebriDx immunoassay for triaging patients with suspected coronavirus disease 2019 (COVID-19) upon admission to healthcare facilities. An electronic search was conducted in Scopus and Medline using the keywords ‘FebriDx’ AND ‘COVID-19’ OR ‘SARS-CoV-2’, with no language or date (i.e. up to 4^th February 2022) limits, selecting studies where FebriDx was used for triaging patients with suspected COVID-19 in acute care settings, and reporting sufficient data to construct a 2×2 table. Five studies were included in the final analysis, totalling 2309 patients. The pooled diagnostic sensitivity and specificity were 0.91 [95% confidence interval (CI) 0.88–0.93] and 0.92 (95% CI 0.90–0.93), whilst the area under the curve, accuracy and kappa statistics were 0.971 (95% CI 0.962–0.980), 91.4% (95% CI 90.2–92.5%) and 0.762 (95% CI 0.731–0.793), respectively, thus reflecting substantial agreement with reference molecular testing techniques. Negative and positive predictive values were 0.974 (95% CI 0.966–0.981) and 0.742 (95% CI 0.711–0.770), respectively. This pooled analysis demonstrated that FebriDx has clinical value for rapid screening of patients with suspected COVID-19 in acute care settings, especially in regions with high viral circulation in which the pre-test probability is high, and enables prioritization for confirmatory laboratory testing.