key: cord-1005435-g2op871k
authors: Karim, Nawazish; Ashraf, Muhammad Zubair; Naeem, Muhammad; Anwar, Tahir; Aung, Hnin; Mallik, Srikumar; Avraam, Eleni; Kiran, Sidra; Bandapaati, Sareesh; Khan, Faisal; Tsaknis, Georgios; Reddy, Raja
title: Utility of the FebriDx point‐of‐care test for rapid triage and identification of possible coronavirus disease 2019 (COVID‐19)
date: 2020-09-17
journal: Int J Clin Pract
DOI: 10.1111/ijcp.13702
sha: 41c5e1c00af4a4c08ccd97f3547e87866723d83c
doc_id: 1005435
cord_uid: g2op871k

OBJECTIVES: The Coronavirus disease 2019 (COVID‐19) pandemic is straining healthcare resources. Molecular testing turnaround time precludes having results at the point‐of‐care (POC) thereby exposing COVID‐19/Non‐COVID‐19 patients while awaiting diagnosis. We evaluated the utility of a triage strategy including FebriDx, a 10‐minute POC finger‐stick blood test that differentiates viral from bacterial acute respiratory infection through detection of Myxovirus‐resistance protein A (MxA) and C‐reactive protein (CRP), to rapidly isolate viral cases requiring confirmatory testing. METHODS: This observational, prospective, single‐center study enrolled patients presenting to/within an acute care hospital in England with suspected COVID‐19 between March and April 2020. Immunocompetent patients ≥16 years requiring hospitalisation with pneumonia or acute respiratory distress syndrome or influenza‐like illness (fever and ≥1 respiratory symptom within 7 days of enrolment, or inpatients with new respiratory symptoms, fever of unknown cause or pre‐existing respiratory condition worsening). The primary endpoint was diagnostic performance of FebriDx to identify COVID‐19 as a viral infection; secondary endpoint was SARS‐CoV‐2 molecular test diagnostic performance compared with the reference standard COVID‐19 Case Definition (molecular or antibody detection of SARS‐CoV‐2). RESULTS: Valid results were available for 47 patients. By reference standard, 35 had viral infections (34/35 COVID‐19; 1/35 non‐COVID‐19; overall FebriDx viral sensitivity 97.1% (95%CI 83.3‐99.9)). Of the COVID‐19 cases, 34/34 were FebriDx viral positive (sensitivity 100%; 95%CI 87.4‐100); 29/34 had an initial SARS‐CoV‐2 positive molecular test (sensitivity 85.3%; 95%CI 68.2‐94.5). FebriDx was viral negative when the diagnosis was not COVID‐19 and SARS‐Cov‐2 molecular test was negative (negative predictive value (NPV) 100% (13/13; 95%CI 71.7‐100)) exceeding initial SARS‐CoV‐2 molecular test NPV 72.2% (13/19; 95%CI 46.4‐89.3). The diagnostic specificity of FebriDx and initial SARS‐CoV‐2 molecular test was 100% (13/13; 95%CI 70‐100 and 13/13; 95%CI 85.4‐100, respectively). CONCLUSIONS: FebriDx could be deployed as part of a reliable triage strategy for identifying symptomatic cases as possible COVID‐19 in the pandemic.

Acute respiratory infection (ARI) is the most common reason patients seek healthcare worldwide. Uncomplicated ARIs in the outpatient setting are often of viral origin [acute bronchitis (90%), pharyngitis (85%), and sinusitis (98%)] or are self-limiting and tend to resolve without antibiotics. 1 Reliable differentiation between uncomplicated and self-limiting viral from bacterial ARIs remains challenging, primarily due to the non-specific overlapping clinical manifestations which can be present in both clinical scenarios, and secondly because many patients are carriers of or are colonised with bacterial or viral pathogens. 2, 3 The coronavirus disease 2019 (COVID-19) pandemic is putting an extraordinary strain on healthcare resources. To date, molecular reverse transcriptase polymerase chain reaction (rRT-PCR) has been used for screening and initial diagnosis 4-6 despite long turnaround times that can take upwards of 48 hours from sample collection to result. 7 Some patients, including those with high likelihood COVID-19 infection who present symptomatic (eg, fever, cough, shortness of breath or sudden onset of anosmia, ageusia or dysgeusia) with recent exposure (within 14 days) and chest imaging consistent with COVID-19 infection (eg, ground-glass opacities, multifocal organising pneumonia and architectural distortion in a peripheral distribution), 5, 8 test negative on the initial rRT-PCR test which requires multiple, between 2 and 4 subsequent tests, to return an eventual positive result. [9] [10] [11] Variations of sampling techniques, viral load at the time of testing may impact sensitivity and false negative rates due to insufficient quantity of viral ribonucleic acid (RNA) to meet the manufacture's test kit limit of detection (LOD). 12 Additionally, analytical sensitivity of the manufacturer test kit may impact sensitivity such as a limit of detection (LOD) that is too high would result in patients with SARS-CoV-2 testing negative and thereby increasing the false negative rate. 12, 13 Molecular tests are also impacted by efficiency of viral sample transfer to the test and can differ depending on sampling technique (oropharyngeal vs. nasopharyngeal). 14, 15 This may offer an explanation as to why early data from China reported test sensitivities ranging from 66% to 70% which results in false negative rates ranging from 34% to 30%. 12, 16 Studies comparing rRT-PCR to a composite of radiological plus clinical findings (signs/symptoms, epidemiological evidence of exposure) have reported that chest imaging improves initial diagnosis of COVID-19 and is associated with fewer false negatives; Ai and colleagues reported a decrease in false negative diagnosis from 25% (initial rRT-PCR) to 3% (chest imaging) whereas Long et al, found that false negative diagnosis decreased from 16 .7% (initial rRT-PCR) to 2.8% (chest imaging) when chest imaging was included in the initial diagnosis of COVID-19. 9, 17 Therefore, a comprehensive clinical diagnosis inclusive of clinical exam (symptoms/signs), laboratory findings, confirmatory testing (ie, rRT-PCR), and chest imaging (chest computed tomography (CT)) may also be considered as indictors of COVID-19 to reduce false negative rate of molecular testing. [17] [18] [19] [20] Rapid host response assays have been proposed for initial triage as components of a comprehensive COVID-19 diagnostic strategy that also includes molecular and antibody testing. This is in an effort to streamline patients for confirmatory testing, quarantine and facilitate hospitalisation or discharge. 21 FebriDx, (Lumos Diagnostics, Sarasota, FL, USA) is a point-of-care (POC) immunoassay that rapidly (10 minutes) assesses a host immune response to an ARI and dif-

Myxovirus resistance protein A (MxA) and C-reactive protein (CRP) from a fingerstick blood sample. C-reactive protein (CRP) is a non-specific, acute-phase protein that is upregulated due to acute inflammation, including response to infection and is predominately produced by the liver in response to inflammatory cytokines such as interleukin (IL)-6. [22] [23] [24] [25] [26] [27] [28] [29] [30] MxA is an intracellular protein that is exclusively induced by type I interferon (IFN) and not by other cytokines expressed during bacterial infection (eg, IFN-gamma, IL-1, tumour necrosis factor (TNF)-alpha). 31 Type I IFNs are produced by many different cell types, specifically monocytes and macrophages, in response to a wide range of viral infections and are found to be elevated in the presence of most acute viral infections. [32] [33] [34] Therefore, MxA is upregulated in response to an acute viral infection and remains low in bacterial infections. 32, 33 It is hypothesised that SARS-CoV-2 may initially suppress type I IFN production causing loss of viral containment early in of infection followed by an influx of neutrophils, macrophages and excessive production of type I IFN. 35 Therefore, we hypothesised that FebriDx would provide an early indication of a host immune response in suspected COVID-19 cases presenting to or within the hospital. Identifying patients as having a bacterial or viral infection or non-infectious condition could significantly decrease time to presumed diagnosis and allow for appropriate isolation from the outset. The primary objective was to assess the FebriDx assay ability to identify COVID-19 patients as viral infections in order to inform clinical management strategies and initial isolation procedures until confirmatory testing results are available.

Patients presenting between March 16 and April 3, 2020 to the emergency department (ED) or within a hospital ward of Kettering General Hospital, a 600-bed acute care hospital serving a population of 330 000 of middle (mainly)-to low income Caucasians in Kettering, England, with suspected COVID-19 infection were prospectively screened for eligibility. Patients were considered to be eligible if they were 16 years or older, met the Public Health England (PHE) criteria for swab testing for COVID-19 which included the requirement of hospital admission and having either clinical or radiological evidence of pneumonia or acute respiratory distress syndrome or influenza-like illness (fever ≥ 37.8°C and at least one of the following respiratory symptoms, which must be of acute onset (within 7 days of enrollment): persistent cough (with or without sputum), hoarseness, nasal discharge or congestion, shortness of breath, sore throat, wheezing, sneezing), or inpatients with new respiratory symptoms or fever without another cause or worsening of a preexisting respiratory condition. 6 Patients were not eligible if they did not consent to participate, did not meet PHE criteria for COVID-19 swab testing, received a live vaccine or antivirals in the last 14 days, had respiratory symptoms for more than 7 days, or were taking immunosuppressive therapy or systemic corticosteroids. Consent was obtained from patients prior to inclusion in the study. The POC FebriDx test was offered by study physicians at the time nurses performed the nasal and pharyngeal swab for viral PCR testing (SARS-CoV-2, Influenza A, Influenza B and Respiratory Syncytial Virus (RSV)). Study physicians preformed, interpreted and documented the FebriDx test results at the time of testing and were blinded of the SARS-CoV-2 rRT-PCR test results which were not available for 2-4 days following the FebriDx test. Standard routine blood tests (eg, complete blood cell count (CBC), CRP and procalcitonin (PCT)) were also performed and unblinded to study and treating physicians. 

The FebriDx test procedure is simple, performed in approximately 

Evaluate the diagnostic performance of FebriDx to identify Bacterial Infection in hospitalised patients with suspected ARI. The diagnostic performance of the initial SARS-CoV-2 rRT-PCR test as compared with the Case Definition for COVID-19 (ie, positive SARS-CoV-2 rRT-PCR or antibody test).

Sample size was not prespecified. The data were summarised using descriptive statistics and results are reported as medians and interquartile ranges or means and standard deviations, as appropriate.

Categorical variables are summarised numerically and percentages. 

A total of 75 consecutive patients were screened for eligibility and 26 patients were deemed ineligible due to history of symptoms being longer than 7 days in duration (n = 25) and immunosuppression (n = 1). FebriDx testing was performed on 49 patients, test results were obtained for 48/49 patients as testing was not possible in one patient due to an inability to obtain enough blood on the first at- Cohort characteristics are described in Table 1 . 

Our findings demonstrate that FebriDx can be used to rapidly identify suspected cases of COVID-19 in symptomatic patients presenting to F I G U R E 2 Screened and enrolled patients and within the hospital with a high degree of accuracy. Additionally, our study found that rRT-PCR was highly specific for SARS-CoV-2 and also noted a lower false negative rate compared with previous studies (15% vs. 30% respectively), 12 This would help avoid unnecessary exposure while awaiting confirmatory rRT-PCR testing. Furthermore, if the FebriDx result is "viral negative" an alternative diagnosis such as bacterial infection or non-infectious conditions such as acute exacerbation of chronic obstructive pulmonary disease, asthma or heart failure, should be considered at the outset.

ideally, by optimising all available diagnostic tools (eg, clinical assessment, host response, molecular testing, antibody testing etc). 21 Pulia

that incorporates a comprehensive approach that could be used in the SARS-CoV-2 pandemic and potentially as a general strategy in future pandemics. 21 The strategy proposes that after initial screening (eg, clinical signs/symptoms of the suspected infection), such as the initial screening performed in our study, patients could be (i) be quickly tested for a viral, bacterial or absent immune response to an infection, followed by (ii) rapid confirmatory pathogen-specific testing; and (iii) rapid antibody testing could be performed in patients that present with greater than 7 days of symptom onset to test. 40 The same appears to apply to procalcitonin and leucocyte count in our study (Table 1) . This strategy allowed us to obtain a maximum number of potential symptoms were generally immunocompetent adults and our study only included immunocompetent adults. Therefore, additional studies would be required to assess this strategy in children as well as immunocompromised patients.

According to overwhelming data reports from the PHE, CDC and ECDC, as well as based on experience in our own clinical setting, the predominant virus causing hospitalisation amongst adults at present, seems to be SARS-CoV-2. Based on our study findings, we provide evidence that FebriDx could be deployed as part of the initial diagnostic triage strategy for identification of symptomatic COVID-19 patients presenting in a hospital setting.

We thank the participants of the study. Lumos Diagnostic provided editorial support, but had no role in the study design, conduct of the study, data collection and analysis. Study conclusions are based on the author's interpretation of the results.

Authors declare that they have no conflicts of interest.

The datasets during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Prior to enrollment, the study was submitted for review to the 

Appropriate antibiotic use for acute respiratory tract infection in adults: advice for high-value care from the American College of Physicians and the Centers for Disease Control and Prevention

Group A Streptococcus pharyngitis and pharyngeal carriage: a meta-analysis

Diagnosis of streptococcal pharyngitis: differentiation of active infection from the carrier state in the symptomatic child

Evaluating and Testing Persons for Coronavirus Disease

Case definition for coronavirus disease 2019 (COVID-19), as of 29

Guidance COVID-19: investigation and initial clinical management of possible cases 2020

Coronavirus (COVID-19): getting tested

COVID-19): 2020 Interim Case Definition

Correlation of chest CT and RT-PCR testing in coronavirus disease 2019 (COVID-19) in China: a report of 1014 cases

False-negative results of real-time reverse-transcriptase polymerase chain reaction for severe acute respiratory syndrome coronavirus 2: role of deep-learningbased CT diagnosis and insights from two cases

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Epidemiological and clinical predictors of COVID-19

False negative tests for SARS-CoV-2 infection-challenges and implications

Variation in false-negative rate of reverse transcriptase polymerase chain reaction-based SARS-CoV-2 tests by time since exposure

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Measurement of C-reactive protein and the erythrocyte sedimentation rate in general practice

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The value of C-reactive protein as a marker of bacterial infection in patients with septicaemia/endocarditis and influenza

Value of the C-reactive protein test in the differentiation of bacterial and viral pneumonia

C-reactive protein in acute viral infections

Acute phase reactants in predicting disease outcome. Bailliere's

C-reactive protein: a critical review

Interferons: cell signalling, immune modulation, antiviral response and virus countermeasures

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Immune responses in COVID-19 and potential vaccines: lessons learned from SARS and MERS epidemic

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Effect of procalcitonin-based guidelines vs standard guidelines on antibiotic use in lower respiratory tract infections: the ProHOSP randomized controlled trial

Pneumonia: diagnosis and management of community and hospital acquired pneumonia in adults

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