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

Towards improved point-of-care (POC) testing for patients with suspected sepsis: POC tests for host biomarkers and possible microbial pathogens

INTRODUCTION

Sepsis is a heterogeneous syndrome often misdiagnosed. Point-of-care (POC) diagnostic tests are commonly used to guide decision and include host biomarkers and molecular diagnostics.

AREAS COVERED

The diagnostic and prognostic accuracy of established and emerging biomarkers for sepsis, including procalcitonin (PCT) soluble urokinase plasminogen activator receptor (suPAR), presepsin, TRAIL/IP-10/CRP, MxA, and MxA-CRP, are analyzed in this review. The clinical utility of the two prevalent molecular techniques for pathogens identification using polymerase chain reaction (PCR) assays is also presented: FILMARRAY and QIAstat-Dx RP.

EXPERT OPINION

The rising benefits of the combined use of POC biomarkers with molecular diagnostics in daily clinical routine appear to outperform conventional practices in terms of reduced turnaround time, timely diagnosis, and prompt administration of the appropriate treatment. Yet, this must be further demonstrated in future investigations. However, the cost-effectiveness of POC tests and the high rate of false positive and negative results, indicate the need for a comprehensive clinical evaluation.

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.

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).

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

OBJECTIVES

Patients presenting to hospital with suspected coronavirus disease 2019 (COVID-19), based on clinical symptoms, are routinely placed in a cohort together until polymerase chain reaction (PCR) test results are available. This procedure leads to delays in transfers to definitive areas and high nosocomial transmission rates. FebriDx is a finger-prick point-of-care test (PoCT) that detects an antiviral host response and has a high negative predictive value for COVID-19. We sought to determine the clinical impact of using FebriDx for COVID-19 triage in the emergency department (ED).

DESIGN

We undertook a retrospective observational study evaluating the real-world clinical impact of FebriDx as part of an ED COVID-19 triage algorithm.

SETTING

Emergency department of a university teaching hospital.

PATIENTS

Patients presenting with symptoms suggestive of COVID-19, placed in a cohort in a 'high-risk' area, were tested using FebriDx. Patients without a detectable antiviral host response were then moved to a lower-risk area.

RESULTS

Between September 22, 2020, and January 7, 2021, 1,321 patients were tested using FebriDx, and 1,104 (84%) did not have a detectable antiviral host response. Among 1,104 patients, 865 (78%) were moved to a lower-risk area within the ED. The median times spent in a high-risk area were 52 minutes (interquartile range [IQR], 34-92) for FebriDx-negative patients and 203 minutes (IQR, 142-255) for FebriDx-positive patients (difference of -134 minutes; 95% CI, -144 to -122; P < .0001). The negative predictive value of FebriDx for the identification of COVID-19 was 96% (661 of 690; 95% CI, 94%-97%).

CONCLUSIONS

FebriDx improved the triage of patients with suspected COVID-19 and reduced the time that severe acute respiratory coronavirus virus 2 (SARS-CoV-2) PCR-negative patients spent in a high-risk area alongside SARS-CoV-2-positive patients.

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.