Utility of the FebriDx point-of-care test for rapid triage and identification of possible coronavirus disease 2019 (COVID-19)

Developing a Tool for Differentiation Between Bacterial and Viral Respiratory Infections Using Myxovirus Resistance Protein A and C-Reactive Protein

INTRODUCTION

The aim was to assess the performance of a blood assay combining measurements of MxA (myxovirus resistance protein A) and CRP (C-reactive protein) to differentiate viral from bacterial respiratory infections.

METHODS

In a prospective study, MxA and CRP were measured in the blood by the AFIAS panel in adults admitted with respiratory infection. Patients were split into discovery and validation cohorts. Final diagnosis was adjudicated by a panel of experts. Microbiology-confirmed cases comprised the discovery cohort, and infections adjudicated as highly probable viral or bacterial comprised the validation cohort.

RESULTS

A total of 537 patients were analyzed: 136 patients were adjudicated with definitive viral infections and 131 patients with definitive bacterial infections. Using logistic regression analysis, an equation was developed to calculate the probability for bacterial infection using the absolute value of MxA and CRP. Calculated probability ≥ 0.5 and/or MxA to CRP ratio less than 2 applied as the diagnostic rule for bacterial infections. This rule provided 91.6% sensitivity and 90.4% negative predictive value for the diagnosis of bacterial infections. This diagnostic sensitivity was confirmed in the validation cohort. A MxA/CRP ratio less than 0.15 was associated with unfavorable outcome.

CONCLUSION

The calculation of the probability for bacterial infection using MxA and CRP may efficiently discriminate between viral and bacterial respiratory infections.

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.

MxA for differentiating viral and bacterial infections in adults: a prospective, exploratory study

PURPOSE

Inappropriate antibiotic prescription in patients with viral infections contributes to the surge of antibiotic resistance. Viral infections induce the expression of the antiviral protein MxA in monocytes, which is a promising biomarker to differentiate between viral and bacterial diseases. In this prospective, exploratory study, we aimed to determine the diagnostic value of monocyte MxA expression in adults with viral, bacterial or co-infections.

METHODS

We measured monocyte MxA expression using flow cytometry in a cohort of 61 adults with various viral, bacterial and co-infections including patients receiving immunosuppressive therapy.

RESULTS

Monocyte MxA expression in virus-infected patients was significantly higher compared to bacterial infections (83.3 [66.8, 109.4] vs. 33.8 [29.3, 47.8] mean fluorescence intensity [MFI]; p < 0.0001) but not co-infections (53.1 [33.9, 88.9] MFI). At a threshold of 62.2 MFI, the area under the ROC curve (AUC) to differentiate between viral and bacterial infections was 0.9, with a sensitivity and specificity of 92.3% and 84.6%, respectively. Immunosuppressive therapy did not affect monocyte MxA expression in virus-infected patients.

CONCLUSION

Our findings corroborate the diagnostic performance of MxA in differentiating viral and bacterial infections but also point to an important caveat of MxA in viral-bacterial co-infections. This study extends previous reports and indicates that MxA is also a useful biomarker in immunocompromised patients.

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.

Blood myxovirus resistance protein-1 measurement in the diagnostic work-up of suspected COVID-19 infection in the emergency department

INTRODUCTION

Myxovirus resistance protein 1 (MxA) is a biomarker that is elevated in patients with viral infections. The goal of this study was to evaluate the diagnostic value of MxA in diagnosing COVID-19 infections in the emergency department (ED) patients.

METHODS

This was a single-center prospective observational cohort study including patients with a suspected COVID-19 infection. The primary outcome of this study was a confirmed COVID-19 infection by RT-PCR test. MxA was assessed using an enzyme immunoassay on whole blood and receiver operating chart and area under the curve (AUC) analysis was conducted. Sensitivity, specificity, negative predictive value, and positive predictive value of MxA on diagnosing COVID-19 at the optimal cut-off of MxA was determined.

RESULTS

In 2021, 100 patients were included. Of these patients, 77 patients had COVID-19 infection and 23 were non-COVID-19. Median MxA level was significantly higher (p < .001) in COVID-19 patients compared to non-COVID-19 patients, respectively 1933 and 0.1 ng/ml. The AUC of MxA on a confirmed COVID-19 infection was 0.941 (95% CI: 0.867-1.000). The optimal cut-off point of MxA was 252 ng/ml. At this cut-off point, the sensitivity of MxA on a confirmed COVID-19 infection was 94% (95% CI: 85%-98%) and the specificity was 91% (95% CI: 72%-99%).

CONCLUSION

MxA accurately distinguishes COVID-19 infections from bacterial infections and noninfectious diagnoses in the ED in patients with a suspected COVID-19 infection. If the results can be validated, MxA could improve the diagnostic workup and patient flow in the ED.

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.

Economic Evaluation of FebriDx®: A Novel Rapid, Point-of-Care Test for Differentiation of Viral versus Bacterial Acute Respiratory Infection in the United States

Background: Acute respiratory infections (ARIs) are commonly treated with antibiotics in outpatient settings, but many infections are caused by viruses and antibiotic treatment is therefore inappropriate. FebriDx®, a rapid point-of-care test that can differentiate viral from bacterial infections, can inform antibiotic treatment decisions. Objectives: The primary aim of this study is to conduct a literature-based US economic evaluation of a novel rapid point-of-care test, FebriDx®, that simultaneously measures two key infection biomarkers, C-reactive protein (CRP) and Myxovirus resistance protein A (MxA), to accurately differentiate viral from bacterial infection. Methods: A budget impact model was developed based on a review of published literature on antibiotic prescribing for ARIs in the United States. The model considers the cost of antibiotic treatment, antibiotic resistant infections, antibiotic-related adverse events, and point-of-care testing. These costs were extrapolated to estimate savings on a national level. Results: The expected national cost to treat ARIs under standard of care was US $8.25 billion, whereas the expected national cost of FebriDx point-of-care-guided ARI treatment was US $5.74 billion. Therefore, the expected national savings associated with FebriDx® rapid point-of-care testing was US $2.51 billion annually. Conclusions: FebriDx, a point of care test that can reliably aid in the differentiation of viral and bacterial infections, can reduce antibiotic misuse and, therefore, antibiotic resistant infections. This results in significant cost savings, driven primarily by the reduction in antibiotic resistant infections.

Utility of the FebriDx point-of-care assay in supporting a triage algorithm for medical admissions with possible COVID-19: an observational cohort study

OBJECTIVE

To evaluate a triage algorithm used to identify and isolate patients with suspected COVID-19 among medical patients needing admission to hospital using simple clinical criteria and the FebriDx assay.

DESIGN

Retrospective observational cohort.

SETTING

Large acute National Health Service hospital in London, UK.

PARTICIPANTS

All medical admissions from the emergency department between 10 August 2020 and 4 November 2020 with a valid SARS-CoV-2 RT-PCR result.

INTERVENTIONS

Medical admissions 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 positive for myxovirus resistance protein A (a host response protein) were managed as likely COVID-19.

PRIMARY OUTCOME MEASURES

Diagnostic accuracy (sensitivity, specificity and predictive values) of the algorithm and the FebriDx assay using SARS-CoV-2 RT-PCR from nasopharyngeal swabs as the reference standard.

RESULTS

4.0% (136) of 3443 medical admissions had RT-PCR confirmed COVID-19. Prevalence of COVID-19 was 46% (80/175) in those triaged as likely, 4.1% (50/1225) in possible and 0.3% (6/2033) in unlikely COVID-19. Using a SARS-CoV-2 RT-PCR reference standard, clinical triage had sensitivity of 96% (95% CI 91% to 98%) and specificity of 61.5% (95% CI 59.8% to 63.1%), while the triage algorithm including FebriDx had sensitivity of 93% (95% CI 87% to 96%) and specificity of 86.4% (95% CI 85.2% to 87.5%). While 2033 patients were deemed not to require isolation using clinical criteria alone, the addition of FebriDx to clinical triage allowed a further 826 patients to be released from isolation, reducing the need for isolation rooms by 9.5 per day, 95% CI 8.9 to 10.2. Ten patients missed by the algorithm had mild or asymptomatic COVID-19.

CONCLUSIONS

A triage algorithm including the FebriDx assay had good sensitivity and was useful to 'rule-out' COVID-19 among medical admissions to hospital.