Rapid, point-of-care antigen and molecular-based tests for diagnosis of SARS-CoV-2 infection

Performance of SARS-CoV-2 rapid antigen test compared with real-time RT-PCR in asymptomatic individuals

Screening, testing and contact tracing plays a pivotal role in control of the COVID-19 pandemic. To enable this it is necessary to increase the testing capacity. This study compared a SARS-CoV-2 rapid antigen test (RAT) and RT-PCR in 842 asymptomatic individuals from Tarapacá, Chile. A sensitivity of 69.86%, specificity of 99.61%, PPV of 94.44% and NPP of 97.22% with Ct values (Ct > 27) that were significantly higher among individuals with false-negative RAT were reported. These results support the fact that RAT might have a significant impact on the identification of asymptomatic carriers in areas that lack suitable laboratories to perform SARS-CoV-2 real-time RT-PCR diagnostics, or the results take more than 24-48 h, as well as zones with high traffic of individuals such as border/customs, airports, interregional bus, train stations or in any mass testing campaign requiring rapid results.

Nano-therapeutic strategies to target coronavirus

The coronaviruses have caused severe acute respiratory syndrome (SARS), the Middle East respiratory syndrome (MERS), and the more recent coronavirus pneumonia (COVID-19). The global COVID-19 pandemic requires urgent action to develop anti-virals, new therapeutics, and vaccines. In this review, we discuss potential therapeutics including human recombinant ACE2 soluble, inflammatory cytokine inhibitors, and direct anti-viral agents such as remdesivir and favipiravir, to limit their fatality. We also discuss the structure of the SARS-CoV-2, which is crucial to the timely development of therapeutics, and previous attempts to generate vaccines against SARS-CoV and MERS-CoV. Finally, we provide an overview of the role of nanotechnology in the development of therapeutics as well as in the diagnosis of the infection. This information is key for computational modeling and nanomedicine-based new therapeutics by counteracting the variable proteins in the virus. Further, we also try to effectively share the latest information about many different aspects of COVID-19 vaccine developments and possible management to further scientific endeavors.

Modelling of hypothetical SARS-CoV-2 point of care tests for routine testing in residential care homes: rapid cost-effectiveness analysis

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus that causes coronavirus disease 2019 (COVID-19), which at the time of writing (January 2021) was responsible for more than 2.25 million deaths worldwide and over 100,000 deaths in the UK. SARS-CoV-2 appears to be highly transmissible and could rapidly spread in residential care homes.

OBJECTIVE

The work undertaken aimed to estimate the clinical effectiveness and cost-effectiveness of viral detection point-of-care tests for detecting SARS-CoV-2 compared with laboratory-based tests in the setting of a hypothetical care home facility for elderly residents.

PERSPECTIVE/SETTING

The perspective was that of the NHS in 2020. The setting was a hypothetical care home facility for elderly residents. Care homes with en suite rooms and with shared facilities were modelled separately.

METHODS

A discrete event simulation model was constructed to model individual residents and simulate the spread of SARS-CoV-2 once it had entered the residential care facility. The numbers of COVID-19-related deaths and critical cases were recorded in addition to the number of days spent in isolation. Thirteen strategies involving different hypothetical SARS-CoV-2 tests were modelled. Recently published desirable and acceptable target product profiles for SARS-CoV-2 point-of-care tests and for hospital-based SARS-CoV-2 tests were modelled. Scenario analyses modelled early release from isolation based on receipt of a negative SARS-CoV-2 test result and the impact of vaccination. Incremental analyses were undertaken using both incremental cost-effectiveness ratios and net monetary benefits.

RESULTS

Cost-effectiveness results depended on the proportion of residential care facilities penetrated by SARS-CoV-2. SARS-CoV-2 point-of-care tests with desirable target product profiles appear to have high net monetary benefit values. In contrast, SARS-CoV-2 point-of-care tests with acceptable target product profiles had low net monetary benefit values because of unnecessary isolations. The benefit of allowing early release from isolation depended on whether or not the facility had en suite rooms. The greater the assumed efficacy of vaccination, the lower the net monetary benefit values associated with SARS-CoV-2 point-of-care tests, when assuming that a vaccine lowers the risk of contracting SARS-CoV-2.

LIMITATIONS

There is considerable uncertainty in the values for key parameters within the model, although calibration was undertaken in an attempt to mitigate this. Some degree of Monte Carlo sampling error persists because of the timelines of the project. The example care home simulated will also not match those of decision-makers deciding on the clinical effectiveness and cost-effectiveness of introducing SARS-CoV-2 point-of-care tests. Given these limitations, the results should be taken as indicative rather than definitive, particularly the cost-effectiveness results when the relative cost per SARS-CoV-2 point-of-care test is uncertain.

CONCLUSIONS

SARS-CoV-2 point-of-care tests have considerable potential for benefit for use in residential care facilities, but whether or not this materialises depends on the diagnostic accuracy and costs of forthcoming SARS-CoV-2 point-of-care tests.

FUTURE WORK

More accurate results would be obtained when there is more certainty on the diagnostic accuracy of and the reduction in time to test result associated with SARS-CoV-2 point-of-care tests when used in the context of residential care facilities, the proportion of care home penetrated by SARS-CoV-2 and the levels of immunity once vaccination is administered. These parameters are currently uncertain.

FUNDING

This report was commissioned by the National Institute for Health Research (NIHR) Evidence Synthesis programme as project number 132154. This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 25, No. 39. See the NIHR Journals Library website for further project information.

Current and innovative methods for the diagnosis of COVID‑19 infection (Review)

The Coronavirus Disease 2019 (COVID‑19) pandemic has forced the scientific community to rapidly develop highly reliable diagnostic methods in order to effectively and accurately diagnose this pathology, thus limiting the spread of infection. Although the structural and molecular characteristics of the severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) were initially unknown, various diagnostic strategies useful for making a correct diagnosis of COVID‑19 have been rapidly developed by private research laboratories and biomedical companies. At present, rapid antigen or antibody tests, immunoenzymatic serological tests and molecular tests based on RT‑PCR are the most widely used and validated techniques worldwide. Apart from these conventional methods, other techniques, including isothermal nucleic acid amplification techniques, clusters of regularly interspaced short palindromic repeats/Cas (CRISPR/Cas)‑based approaches or digital PCR methods are currently used in research contexts or are awaiting approval for diagnostic use by competent authorities. In order to provide guidance for the correct use of COVID‑19 diagnostic tests, the present review describes the diagnostic strategies available which may be used for the diagnosis of COVID‑19 infection in both clinical and research settings. In particular, the technical and instrumental characteristics of the diagnostic methods used are described herein. In addition, updated and detailed information about the type of sample, the modality and the timing of use of specific tests are also discussed.

Current and innovative methods for the diagnosis of COVID‑19 infection (Review)

The Coronavirus Disease 2019 (COVID‑19) pandemic has forced the scientific community to rapidly develop highly reliable diagnostic methods in order to effectively and accurately diagnose this pathology, thus limiting the spread of infection. Although the structural and molecular characteristics of the severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) were initially unknown, various diagnostic strategies useful for making a correct diagnosis of COVID‑19 have been rapidly developed by private research laboratories and biomedical companies. At present, rapid antigen or antibody tests, immunoenzymatic serological tests and molecular tests based on RT‑PCR are the most widely used and validated techniques worldwide. Apart from these conventional methods, other techniques, including isothermal nucleic acid amplification techniques, clusters of regularly interspaced short palindromic repeats/Cas (CRISPR/Cas)‑based approaches or digital PCR methods are currently used in research contexts or are awaiting approval for diagnostic use by competent authorities. In order to provide guidance for the correct use of COVID‑19 diagnostic tests, the present review describes the diagnostic strategies available which may be used for the diagnosis of COVID‑19 infection in both clinical and research settings. In particular, the technical and instrumental characteristics of the diagnostic methods used are described herein. In addition, updated and detailed information about the type of sample, the modality and the timing of use of specific tests are also discussed.

Care pathway and prioritization of rapid testing for COVID-19 in UK hospitals: a qualitative evaluation

OBJECTIVES

The second wave of the coronavirus pandemic is now established, occurring at a time of winter pressure on acute care in the NHS. This is likely to be more challenging then the first wave for the diagnosis of COVID-19 because of the similar symptomology with other respiratory conditions highly prevalent in winter. This study sought to understand the care pathways in place in UK NHS hospitals during the first wave (March-July 2020) for identification of patients with COVID-19 and to learn lessons to inform optimal testing strategies within the COVID-19 National Diagnostic Research and Evaluation Platform (CONDOR).

DESIGN, SETTING & PARTICIPANTS

Sixteen hospital-based clinicians from 12 UK NHS Trusts covering 10 different specialties were interviewed following a semi-structured topic guide. Data were coded soon after the interviews and analysed thematically.

RESULTS

We developed a diagrammatic, high-level visualisation of the care pathway describing the main clinical decisions associated with the diagnosis and management of patients with suspected COVID-19. COVID-19 testing influenced infection control considerations more so than treatment decisions. Two main features of service provision influenced the patient management significantly: access to rapid laboratory testing and the number of single occupancy rooms. If time to return of result was greater than 24 h, patients with a presumptive diagnosis would often be cohorted based on clinical suspicion alone. Undetected COVID-19 during this time could therefore lead to an increased risk of viral transmission.

CONCLUSIONS

During the winter months, priority for provision of rapid testing at admission should be given to hospitals with limited access to laboratory services and single room availability. Access to rapid testing is essential for urgent decisions related to emergency surgery, maternity services and organ transplant. The pathway and prioritization of need will inform the economic modelling, clinical evaluations, and implementation of new clinical tests in UK.

Clinical Application of a New SARS-CoV-2 Antigen Detection Kit (Colloidal Gold) in the Detection of COVID-19

The precise diagnosis of COVID-19 is of outmost importance in order to effectively treat patients and prevent SARS-CoV-2 transmission. Herein, we evaluated the sensitivity and specificity of the COVID-19 Antigen Detection Kit (Colloidal Gold—CG) compared with PCR in nasopharyngeal and nasal samples. A total of 114 positive and 244 negative nasopharyngeal specimens confirmed by PCR were used in this comparative study. When the PCR positive Cycle Threshold (Ct) value was ≤25, CG sensitivity was 100%. When the PCR positive Ct value was ≤33, CG sensitivity was 99%. When the PCR positive Ct value was ≤40, CG sensitivity was 89.47%. Regarding nasal swabs, a total of 109 positive and 250 negative specimens confirmed by PCR were used. When the PCR positive Ct value was ≤25, CG sensitivity was 100%. When the PCR positive Ct value was ≤33, CG sensitivity was 96.12%. When the PCR positive Ct value was ≤37, CG sensitivity was 91.74%. Specificity was above 99% regardless of the Ct value of PCR positivity for both nasopharyngeal and nasal specimens. Overall, the CG showed high sensitivity and specificity when the PCR Ct value was less than 33. Therefore, CG can be used for screening early in the disease course. Confirmatory PCR is essential when a false negative result is suspected.

Diagnosing SARS-CoV-2 with Antigen Testing, Transcription-Mediated Amplification and Real-Time PCR

This study was performed as a head-to-head comparison of the performance characteristics of (1) two SARS-CoV-2-specific rapid antigen assays with real-time PCR as gold standard as well as (2) a fully automated high-throughput transcription-mediated amplification (TMA) assay and real-time PCR in a latent class analysis-based test comparison without a gold standard with several hundred samples in a low prevalence "real world" setting. Recorded sensitivity and specificity of the NADAL and the LumiraDx antigen assays and the Hologic Aptima SARS-CoV-2 TMA assay were 0.1429 (0.0194, 0.5835), 0.7644 (0.7016, 0.8174), and 0.7157 (0, 1) as well as 0.4545 (0.2022, 0.7326), 0.9954 (0.9817, 0.9988), and 0.9997 (not estimable), respectively. Agreement kappa between the positive results of the two antigen-based assays was 0.060 (0.002, 0.167) and 0.659 (0.492, 0.825) for TMA and real-time PCR. Samples with low viral load as indicated by cycle threshold (Ct) values > 30 were generally missed by both antigen assays, while 1:10 pooling suggested higher sensitivity of TMA compared to real-time PCR. In conclusion, both sensitivity and specificity speak in favor of the use of the LumiraDx rather than the NADAL antigen assay, while TMA results are comparably as accurate as PCR, when applied in a low prevalence setting.

Assessment of SARS-CoV-2 rapid antigen tests

Objectives

Point-of-care antigen tests (PoC-AgTs) for the rapid detection of SARS-CoV-2 infection enable screening of additional populations with less effort, independent of laboratories and at a low cost. PoC-AgTs have therefore been included in national testing strategies with additional quality requirements to address limitations in specificity and sensitivity. Information given in the package inserts of the test providers should enable the user to evaluate the performance of a PoC-AgT in advance. The quality of this information has been independently assessed since the Corona Test Ordinance came into force in Germany in October 2020.

Methods

The completeness of analytical and diagnostic performance specifications was assessed for all package inserts publicly available via the Paul Ehrlich Institute (PEI). It was ascertained whether the minimum criteria, recommendations, and extended criteria of the PEI were comprehensibly fulfilled. The number of tests removed from the list by March 2021 was determined.

Results

By the closing date of the survey (17.11.2020), the PEI had listed 165 PoC-AgTs that formally fulfilled the minimum criteria and were thus reimbursed. A total of 78 identical systems were identified. Almost all providers were found to have gaps in the information on the validation results of their tests, meaning that an evaluation of performance is only possible to a limited extent. Until March 2021, 25 non-identical PoC-AgTs have been removed from the list.

Conclusions

Many PoC-AgTs could not be comprehensively evaluated based on the information provided by the provider. Users are therefore dependent on provider-independent sources of information.

Misdiagnosis of SARS-CoV-2: A Critical Review of the Influence of Sampling and Clinical Detection Methods

SARS-CoV-2 infection has generated the biggest pandemic since the influenza outbreak of 1918-1919. One clear difference between these pandemics has been the ability to test for the presence of the virus or for evidence of infection. This review examined the performance characteristics of sample types via PCR detection of the virus, of antibody testing, of rapid viral antigen detection kits and computerised tomography (CT) scanning. It was found that combined detection approaches, such as the incorporation of CT scans, may reduce the levels of false negatives obtained by PCR detection in both symptomatic and asymptomatic patients, while sputum and oral throat washing sample types should take precedence over swabbing when available. Rt-PCR assays for detection of the virus remain the gold-standard method for SARS-CoV-2 diagnosis and can be used effectively on pooled samples for widespread screening. The novel Oxford antibody assay was found to have the highest sensitivity and specificity of four currently available commercial antibody kits but should only be used during a specific timeframe post-symptom onset. Further research into transmission modes between symptomatic and asymptomatic patients is needed. Analysis of the performance characteristics of different sampling and detection methods for SARS-CoV-2 showed that timing of sampling and testing methods used can greatly influence the rate of false-positive and false-negative test results, thereby influencing viral spread.

What we know and dont know on SARS-CoV-2 and COVID-19

Coronavirus disease 2019 (COVID-19), caused by the SARS-CoV-2 virus discovered in December 2019 in Wuhan, China, has had an enormous impact on public health worldwide due to its rapid spread and pandemic behavior, challenges in its control and mitigation, and few therapeutic alternatives. In this review, we summarize the pathophysiological mechanisms, clinical presentation, and diagnostic techniques. In addition, the main lineages and the different strategies for disease prevention are reviewed, with emphasis on the development of vaccines and their different platforms. Finally, some of the currently available therapeutic strategies are summarized. Throughout the article, we point out the current knowns and unknowns at the time of writing this article.

A Comparative NLP-Based Study on the Current Trends and Future Directions in COVID-19 Research

COVID-19 is a global health crisis that has altered human life and still promises to create ripples of death and destruction in its wake. The sea of scientific literature published over a short time-span to understand and mitigate this global phenomenon necessitates concerted efforts to organize our findings and focus on the unexplored facets of the disease. In this work, we applied natural language processing (NLP) based approaches on scientific literature published on COVID-19 to infer significant keywords that have contributed to our social, economic, demographic, psychological, epidemiological, clinical, and medical understanding of this pandemic. We identify key terms appearing in COVID literature that vary in representation when compared to other virus-borne diseases such as MERS, Ebola, and Influenza. We also identify countries, topics, and research articles that demonstrate that the scientific community is still reacting to the short-term threats such as transmissibility, health risks, treatment plans, and public policies, underpinning the need for collective international efforts towards long-term immunization and drug-related challenges. Furthermore, our study highlights several long-term research directions that are urgently needed for COVID-19 such as: global collaboration to create international open-access data repositories, policymaking to curb future outbreaks, psychological repercussions of COVID-19, vaccine development for SARS-CoV-2 variants and their long-term efficacy studies, and mental health issues in both children and elderly.

Ending the Pandemic: Are Rapid COVID-19 Tests a Step Forward or Back?

Some experts have promoted the use of rapid testing for COVID-19. However, with the current technologies available, continuing to replace laboratory-based, real-time reverse transcription polymerase chain reaction tests with rapid (point-of-care) tests may lead to an increased number of false negative tests. Moreover, the more rapid dissemination of false negative results that can occur with the use of rapid tests for COVID-19 may lead to increased spread of the novel coronavirus if patients do not understand the concept of false negative tests. One means of combatting this would be to tell patients who have a "negative" rapid COVID-19 test that their test result was "indeterminate."

A Generic, Scalable, and Rapid Time-Resolved Förster Resonance Energy Transfer-Based Assay for Antigen Detection-SARS-CoV-2 as a Proof of Concept

The ongoing coronavirus disease 2019 (COVID-19) pandemic has seen an unprecedented increase in the demand for rapid and reliable diagnostic tools, leaving many laboratories scrambling for resources. We present a fast and simple assay principle for antigen detection and demonstrate its functionality by detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens in nasopharyngeal swabs. The method is based on the detection of SARS-CoV-2 nucleoprotein (NP) and S protein (SP) via time-resolved Förster resonance energy transfer (TR-FRET) with donor- and acceptor-labeled polyclonal anti-NP and -SP antibodies. Using recombinant proteins and cell culture-grown SARS-CoV-2, the limits of detection were established as 25 pg of NP or 20 infectious units (IU) and 875 pg of SP or 625 IU. Testing reverse transcription-PCR (RT-PCR)-positive (n = 48, with cycle threshold [CT ] values from 11 to 30) or -negative (n = 96) nasopharyngeal swabs demonstrated that the assay yielded positive results for all samples with CT values of <25 and for a single RT-PCR-negative sample. Virus isolation from the RT-PCR-positive nasopharyngeal swabs showed a strong association between the presence of infectious virus and a positive antigen test result. The NP-based assay showed 97.4% (37/38) sensitivity and 100% (10/10) specificity in comparison with virus isolation and 77.1% (37/48) sensitivity and 99.0% (95/96) specificity in comparison with SARS-CoV-2 RT-PCR. The assay is performed in a buffer that neutralizes SARS-CoV-2 infectivity, and the assay is relatively simple to set up as an "in-house" test. Here, SARS-CoV-2 served as the model pathogen, but the assay principle is applicable to other viral infections, and the test format could easily be adapted to high-throughput testing.IMPORTANCE PCR is currently the gold standard for the diagnosis of many acute infections. While PCR and its variants are highly sensitive and specific, the time from sampling to results is measured in hours at best. Antigen tests directly detect parts of the infectious agent, which may enable faster diagnosis but often at lower sensitivity and specificity. Here, we describe a technique for rapid antigen detection and demonstrate the test format's potential using SARS-CoV-2 as the model pathogen. The 10-min test, performed in a buffer that readily inactivates SARS-CoV-2, from nasopharyngeal samples identified 97.4% (37/38) of the samples from which we could isolate the virus. This suggests that the test performs well in identifying patients potentially shedding the virus. Although SARS-CoV-2 served as the model pathogen to demonstrate proof of concept, the test principle itself would be applicable to a wide variety of infectious and perhaps also noninfectious diseases.

Evaluation of the test accuracy of a SARS-CoV-2 rapid antigen test in symptomatic community dwelling individuals in the Netherlands

Background

SARS-CoV-2 real-time reverse transcriptase polymerase chain reaction (qRT-PCR) is well suited for the diagnosis of clinically ill patients requiring treatment. Application for community testing of symptomatic individuals for disease control purposes however raises challenges. SARS-CoV-2 rapid antigen tests might offer an alternative, but quality evidence on their performance is limited.

Methods

We conducted an evaluation of the test accuracy of the ‘BD Veritor System for Rapid Detection of SARS-CoV-2’ (VRD) compared to qRT-PCR on combined nose/throat swabs obtained from symptomatic individuals at Municipal Health Service (MHS) COVID-19 test centers in the Netherlands. In part one of the study, with the primary objective to evaluate test sensitivity and specificity, all adults presenting at one MHS test center were eligible for inclusion. In part two, with the objective to evaluate test sensitivity stratified by Ct (cycle threshold)-value and time since symptom onset, adults who had a positive qRT-PCR obtained at a MHS test center were eligible.

Findings

In part one (n = 352) SARS-CoV-2 prevalence was 4.8%, overall specificity 100% (95%CI: 98·9%-100%) and sensitivity 94·1% (95%CI: 71·1%-100%). In part two (n = 123) the sensitivity was 78·9% (95%CI: 70·6%-85·7%) overall, 89·4% (95% CI: 79·4%-95·6%) for specimen obtained within seven days after symptom onset and 93% (95% CI: 86%-97.1%) for specimen with a Ct-value below 30.

Interpretation

The VRD is a promising diagnostic for COVID-19 testing of symptomatic community-dwelling individuals within seven days after symptom onset in context of disease control. Further research on practical applicability and the optimal position within the testing landscape is needed.

Review of Current COVID-19 Diagnostics and Opportunities for Further Development

Diagnostic testing plays a critical role in addressing the coronavirus disease 2019 (COVID-19) pandemic, caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Rapid and accurate diagnostic tests are imperative for identifying and managing infected individuals, contact tracing, epidemiologic characterization, and public health decision making. Laboratory testing may be performed based on symptomatic presentation or for screening of asymptomatic people. Confirmation of SARS-CoV-2 infection is typically by nucleic acid amplification tests (NAAT), which requires specialized equipment and training and may be particularly challenging in resource-limited settings. NAAT may give false-negative results due to timing of sample collection relative to infection, improper sampling of respiratory specimens, inadequate preservation of samples, and technical limitations; false-positives may occur due to technical errors, particularly contamination during the manual real-time polymerase chain reaction (RT-PCR) process. Thus, clinical presentation, contact history and contemporary phyloepidemiology must be considered when interpreting results. Several sample-to-answer platforms, including high-throughput systems and Point of Care (PoC) assays, have been developed to increase testing capacity and decrease technical errors. Alternatives to RT-PCR assay, such as other RNA detection methods and antigen tests may be appropriate for certain situations, such as resource-limited settings. While sequencing is important to monitor on-going evolution of the SARS-CoV-2 genome, antibody assays are useful for epidemiologic purposes. The ever-expanding assortment of tests, with varying clinical utility, performance requirements, and limitations, merits comparative evaluation. We herein provide a comprehensive review of currently available COVID-19 diagnostics, exploring their pros and cons as well as appropriate indications. Strategies to further optimize safety, speed, and ease of SARS-CoV-2 testing without compromising accuracy are suggested. Access to scalable diagnostic tools and continued technologic advances, including machine learning and smartphone integration, will facilitate control of the current pandemic as well as preparedness for the next one.

Incorporating false negative tests in epidemiological models for SARS-CoV-2 transmission and reconciling with seroprevalence estimates

Susceptible-Exposed-Infected-Removed (SEIR)-type epidemiologic models, modeling unascertained infections latently, can predict unreported cases and deaths assuming perfect testing. We apply a method we developed to account for the high false negative rates of diagnostic RT-PCR tests for detecting an active SARS-CoV-2 infection in a classic SEIR model. The number of unascertained cases and false negatives being unobservable in a real study, population-based serosurveys can help validate model projections. Applying our method to training data from Delhi, India, during March 15-June 30, 2020, we estimate the underreporting factor for cases at 34-53 (deaths: 8-13) on July 10, 2020, largely consistent with the findings of the first round of serosurveys for Delhi (done during June 27-July 10, 2020) with an estimated 22.86% IgG antibody prevalence, yielding estimated underreporting factors of 30-42 for cases. Together, these imply approximately 96-98% cases in Delhi remained unreported (July 10, 2020). Updated calculations using training data during March 15-December 31, 2020 yield estimated underreporting factor for cases at 13-22 (deaths: 3-7) on January 23, 2021, which are again consistent with the latest (fifth) round of serosurveys for Delhi (done during January 15-23, 2021) with an estimated 56.13% IgG antibody prevalence, yielding an estimated range for the underreporting factor for cases at 17-21. Together, these updated estimates imply approximately 92-96% cases in Delhi remained unreported (January 23, 2021). Such model-based estimates, updated with latest data, provide a viable alternative to repeated resource-intensive serosurveys for tracking unreported cases and deaths and gauging the true extent of the pandemic.

Diagnostic accuracy of the Cepheid Xpert Xpress and the Abbott ID NOW assay for rapid detection of SARS-CoV-2: A systematic review and meta-analysis

Rapid and accurate diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection is essential to prevent the spread of the virus. We investigated the diagnostic accuracy of the Xpert Xpress and the ID NOW assays for rapid detection of SARS‐CoV‐2 using a systemic review and meta‐analysis approach. A systematic literature search was performed using PubMed, Embase, and the Cochrane COVID‐19 Study Register. The sensitivity and specificity of these tests for detecting viruses in patients with suspected SARS‐CoV‐2 infection were pooled. We used commercial and laboratory‐developed reverse transcription‐polymerase chain reactions as reference standards. The Quality Assessment of Diagnostic Accuracy Studies‐2 tool was used to assess the risk of bias. We identified 11 studies involving 1734 subjects for the Xpert Xpress assay and 10 studies involving 1778 subjects for the ID NOW assay. The pooled sensitivity and specificity of the Xpert Xpress assay for detection of SARS‐CoV‐2 were 0.99 (95% confidence interval [CI], 0.97 to 0.99) and 0.97 (95% CI, 0.95 to 0.98), respectively. The pooled sensitivity and specificity of the ID NOW assay were 0.79 (95% CI, 0.69 to 0.86) and 1.00 (95% CI, 0.98 to 1.00), respectively. The studies included in our analysis seemed to have low methodological quality. The Xpert Xpress assay showed excellent diagnostic accuracy for rapid detection of SARS‐CoV‐2. However, as the ID NOW assay showed relatively low sensitivity, this test might miss several positive samples.

We examined the accuracy of two tests in rapid diagnosis of the SARS‐CoV‐2. The Xpert Xpress assay showed excellent diagnostic accuracy. The ID NOW assay had relatively low pooled sensitivity.

Understanding Laboratory Testing for SARS-CoV-2

The SARS-CoV-2 pandemic has impacted millions of lives worldwide. Molecular assays and serological tests have been approved under EUA (emergency use authorization) by the FDA (food and drug administration), given these unprecedented times. These tests are not only critical for confirming the clinical diagnosis and making therapeutic decisions but also play an important role in the understanding of the epidemiology of the pandemic. There is limited experience with currently available tests and differences may exist among tests even using similar technology. The focus of this review is to improve clinicians' understanding of SARS-CoV-2 test procedures including their limitations. We discuss the impact of different host and environmental factors on test results.

A COVID-19 Test Triage Tool, Predicting Negative Results and Reducing the Testing Burden on Healthcare Systems During a Pandemic

Background: Detecting and isolating cases of COVID-19 are amongst the key elements listed by the WHO to reduce transmission. This approach has been reported to reduce those symptomatic with COVID-19 in the population by over 90%. Testing is part of a strategy that will save lives. Testing everyone maybe ideal, but it is not practical. A risk tool based on patient demographics and clinical parameters has the potential to help identify patients most likely to test negative for SARS-CoV-2. If effective it could be used to aide clinical decision making and reduce the testing burden. Methods: At the time of this analysis, a total of 9,516 patients with symptoms suggestive of Covid-19, were assessed and tested at Mount Sinai Institutions in New York. Patient demographics, clinical parameters and test results were collected. A robust prediction pipeline was used to develop a risk tool to predict the likelihood of a positive test for Covid-19. The risk tool was analyzed in a holdout dataset from the cohort and its discriminative ability, calibration and net benefit assessed. Results: Over 48% of those tested in this cohort, had a positive result. The derived model had an AUC of 0.77, provided reliable risk prediction, and demonstrated a superior net benefit than a strategy of testing everybody. When a risk cut-off of 70% was applied, the model had a negative predictive value of 96%. Conclusion: Such a tool could be used to help aide but not replace clinical decision making and conserve vital resources needed to effectively tackle this pandemic.

Analytical Evaluation of Visby Medical RT-PCR Portable Device for Rapid Detection of SARS-CoV-2

Extended community testing constitutes one of the main strategic pillars in controlling the COVID-19 pandemic. Reverse transcription PCR (RT-PCR) targeting the SARS-CoV-2 genome on nasopharyngeal swab samples is currently the reference test. While displaying excellent analytical sensitivity and specificity, this test is costly, often requires a substantial turnaround time, and, more importantly, is subject to reagent and other material shortages. To complement this technology, rapid antigen tests have been developed and made available worldwide, allowing cheap, quick, and decentralized SARS-CoV-2 testing. The main drawback of these tests is the reduced sensitivity when RT-PCR is the gold standard. In this study, we evaluate Visby an innovative, portable, easy-to-use RT-PCR point-of-care (POC) diagnostic device. Our retrospective analysis shows that overall, compared to the Cobas 6800 RT-qPCR assay (Roche), this RT-PCR POC technology detects SARS-CoV-2 RNA with 95% sensitivity (95%CI = 86.3-99%) and 100% specificity (95% CI = 80.5-100%). For samples with cycle-threshold values below 31, we observed 100% sensitivity (95% CI = 66.4-100%). While showing an analytical sensitivity slightly below that of a standard RT-qPCR system, the evaluated Visby RT-PCR POC device may prove to be an interesting diagnostic alternative in the COVID-19 pandemic, potentially combining the practical advantages of rapid antigen tests and the robust analytical performances of nucleic acid detection systems.

Perspective: diagnostic laboratories should urgently develop T cell assays for SARS-CoV-2 infection

Introduction: Diagnostic tests play a critical role in the management of Sars-CoV-2, the virus responsible for COVID-19. There are two groups of tests, which are in widespread use to identify patients who have contracted the virus. The commonly used reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) test becomes negative once viral shedding ceases by approximately 2-3weeks. Antibody tests directed to viral antigens become positive after the second week of infection. IgG antibody responses to the virus are muted in children, pregnant females, and those with mild symptoms. IgA and IgM antibodies rapidly wane, although IgG antibodies directed to the receptor-binding domain (RBD) of the spike (S) glycoprotein are more durable. Current data show variability in the sensitivity of commercial and in-house antibody tests to SARS-CoV-2.Areas covered: The role of T cells in acute illness is uncertain, but long-term protection against the virus may rely on memory T cell responses. Measuring memory T cell responses is important for retrospective confirmation of cases, who may have been infected early in the pandemic before reliable RT-qPCR tests were available and whose SARS-CoV-2 antibodies may have become undetectable. Relevant peer-reviewed published references from PubMed are included up to 15 March 2021.Expert opinion: After surveying the literature, the authors present the case for urgent development of diagnostic T cell assays for SARS-CoV-2 by accredited laboratories.

Preventing COVID-19 spread in closed facilities by regular testing of employees-An efficient intervention in long-term care facilities and prisons?

BACKGROUND

Different levels of control measures were introduced to contain the global COVID-19 pandemic, many of which have been controversial, particularly the comprehensive use of diagnostic tests. Regular testing of high-risk individuals (pre-existing conditions, older than 60 years of age) has been suggested by public health authorities. The WHO suggested the use of routine screening of residents, employees, and visitors of long-term care facilities (LTCF) to protect the resident risk group. Similar suggestions have been made by the WHO for other closed facilities including incarceration facilities (e.g., prisons or jails), wherein parts of the U.S., accelerated release of approved inmates is taken as a measure to mitigate COVID-19.

METHODS AND FINDINGS

Here, the simulation model underlying the pandemic preparedness tool CovidSim 1.1 (http://covidsim.eu/) is extended to investigate the effect of regularly testing of employees to protect immobile resident risk groups in closed facilities. The reduction in the number of infections and deaths within the risk group is investigated. Our simulations are adjusted to reflect the situation of LTCFs in Germany, and incarceration facilities in the U.S. COVID-19 spreads in closed facilities due to contact with infected employees even under strict confinement of visitors in a pandemic scenario without targeted protective measures. Testing is only effective in conjunction with targeted contact reduction between the closed facility and the outside world-and will be most inefficient under strategies aiming for herd immunity. The frequency of testing, the quality of tests, and the waiting time for obtaining test results have noticeable effects. The exact reduction in the number of cases depends on disease prevalence in the population and the levels of contact reductions. Testing every 5 days with a good quality test and a processing time of 24 hours can lead up to a 40% reduction in the number of infections. However, the effects of testing vary substantially among types of closed facilities and can even be counterproductive in U.S. IFs.

CONCLUSIONS

The introduction of COVID-19 in closed facilities is unavoidable without a thorough screening of persons that can introduce the disease into the facility. Regular testing of employees in closed facilities can contribute to reducing the number of infections there, but is only meaningful as an accompanying measure, whose economic benefit needs to be assessed carefully.

Development and performance characteristics evaluation of a new Bioelectric Recognition Assay (BERA) method for rapid Sars-CoV-2 detection in clinical samples

Introduction

As the second wave of COVID-19 pandemic is in progress the development of fast and cost-effective approaches for diagnosis is essential. The aim of the present study was to develop and evaluate the performance characteristics of a new Bioelectric Recognition Assay (BERA) regarding Sars-CoV-2 detection in clinical samples and its potential to be used as a point of care test.

Materials and methods

All tests were performed using a custom portable hardware device developed by EMBIO DIAGNOSTICS (EMBIO DIAGNOSTICS Ltd, Cyprus). 110 positive and 136 negative samples tested by RT-PCR were used in order to define the lower limit of detection (L.O.D.) of the system, as well as the sensitivity and the specificity of the method.

Results

The system was able to detect a viral concentration of 4 genome copies/μL. The method displayed total sensitivity of 92.7 % (95 %CI: 86.2–96.8) and 97.8 % specificity (95 %CI: 93.7–99.5). When samples were grouped according to the recorded Ct values the BERA biosensor displayed 100.00 % sensitivity (95 %CI: 84.6–100.0) for Ct values <20−30. For the aforementioned Ct values the Positive Predictive Value (PPV) of the method was estimated at 31.4 % for COVID-19 prevalence of 1% and at 70.5 % for 5% prevalence. At the same time the Negative Predictive Value (NPV) of the BERA biosensor was at 100.0 % for both prevalence rates.

Conclusions

EMBIO DIAGNOSTICS BERA for the detection of SARS-CoV-2 infection has the potential to allow rapid and cost-effective detection and subsequent isolation of confirmed cases, and therefore reduce household and community transmissions.

Evaluation of a laboratory-based high-throughput SARS-CoV-2 antigen assay for non-COVID-19 patient screening at hospital admission

Several rapid antigen tests (RATs) for the detection of SARS-CoV-2 were evaluated recently. However, reliable performance data for laboratory-based, high-throughput antigen tests are lacking. Therefore and in response to a short-term shortage of PCR reagents, we evaluated DiaSorin's LIAISON SARS-CoV-2 antigen test in comparison to RT-qPCR, and concerning the application of screening non-COVID-19 patients on hospital admission. Applying the manufacturer-recommended cut-off of 200 arbitrary units (AU/mL) the specificity of the LIAISON Test was 100%, the overall analytical sensitivity 40.2%. Lowering the cut-off to 100 AU/mL increased the sensitivity to 49.7% and decreased the specificity to 98.3%. Confining the analysis to samples with an RT-qPCR result < 25 Ct resulted in a sensitivity of 91.2%. The quality of the LIAISON test is very similar to that of good RATs described in the literature with the advantage of high throughput and the disadvantage of relatively long analysis time. It passes the WHO quality criteria for rapid antigen tests and is characterized by particularly high specificity. The LIAISON test can therefore be used for the same applications as recommended for RATs by the WHO. Due to limited sensitivity, the LIAISON test should only be used for screening, if PCR-based assays are not available.

The ID NOW COVID-19, a high-speed high-performance assay

The ID NOW COVID-19 assay is a promising tool for the rapid identification of COVID-19 patients. However, its performances were questioned. We evaluate the ID NOW COVID-19 in comparison to a reference RT-PCR using a collection of 48 fresh nasopharyngeal swabs sampled on universal transport media (UTM). Only 2 false negatives of the ID NOW COVID-19 were identified. They display PCR cycle threshold values of 37.5 and 39.2. The positive percent agreement and the negative percent agreement were 94.9% and 100%, respectively. The Kappa value was 0.88. The ID NOW COVID-19 combines high-speed and accurate processing. Using UTM, the ID NOW COVID-19 could be repeated in the case of invalid result. Further analyses, such as screening of genetic variants or genome sequencing, could also be performed with the same sample. As for all tests, the results should be interpreted according to clinical and epidemiological context.

Five Antigen Tests for SARS-CoV-2: Virus Viability Matters

Antigen testing for SARS-CoV-2 (AGT) is generally considered inferior to RT-PCR testing in terms of sensitivity. However, little is known about the infectiousness of RT-PCR positive patients who pass undetected by AGT. In a screening setting for mildly symptomatic or asymptomatic patients with high COVID-19 prevalence (30-40%), 1141 patients were tested using one of five AGTs and RT-PCR. Where the results differed, virus viability in the samples was tested on cell culture (CV-1 cells). The test battery included AGTs by JOYSBIO, Assure Tech, SD Biosensor, VivaChek Biotech and NDFOS. Sensitivities of the ATGs compared to RT-PCR ranged from 42% to 76%. The best test yielded a 76% sensitivity, 97% specificity, 92% positive, and 89% negative predictive values, respectively. However, in the best performing ATG tests, almost 90% of samples with "false negative" AGT results contained no viable virus. Corrected on the virus viability, sensitivities grew to 81-97% and, with one exception, the tests yielded high specificities >96%. Performance characteristics of the best test after adjustment were 96% sensitivity, 97% specificity, 92% positive, and 99% negative predictive values (high prevalence population). We, therefore, believe that virus viability should be considered when assessing the AGT performance. Also, our results indicate that a well-performing antigen test could in a high-prevalence setting serve as an excellent tool for identifying patients shedding viable virus. We also propose that the high proportion of RT-PCR-positive samples containing no viable virus in the group of "false negatives" of the antigen test should be further investigated with the aim of possibly preventing needless isolation of such patients.

Testing for SARS-CoV-2 seroprevalence: experiences of a tertiary eye centre

INTRODUCTION

The actual prevalence of a SARS-CoV-2 infection and the individual assessment of being or having been infected may differ. Facing the great uncertainty-especially at the beginning of the pandemic-and the possibility of asymptomatic or mildly symptomatic, subclinical infections, we evaluate the experience of SARS-CoV-2 antibody screening at a tertiary clinical setting.

METHODS AND ANALYSIS

All employees of a tertiary eye centre and a research institute of ophthalmology were offered antibody testing in May 2020, using a sequential combination of different validated assays/antigens and point-of-care (POC) testing for a subset (NCT04446338). Before taking blood, a systematic inquiry into past symptoms, known contacts and a subjective self-assessment was documented. The correlations between serostatus, patient contacts and demographic characteristics were analysed. Different tests were compared by Kappa statistics.

RESULTS

Among 318 participants, SARS-CoV-2 antibodies were detected in 9 employees. Chemiluminescence assays (chemiluminescence immunoassay and electrochemiluminescence) showed superior specificity and high reproducibility, compared with ELISA and POC results.In contrast to the low seropositivity (2.8%) of healthcare workers, higher than that of the other departments of the hospital, a large proportion mistakenly assumed that they might have already been infected. Antiviral antibody titres increased and remained on a plateau for at least 3 months.

CONCLUSIONS

The great demand and acceptance confirmed the benefit of highly sensitive testing methods in the early phase of the pandemic. The coincidence of low seroprevalence and anxious employees may have contributed to internalising the need of hygiene measures.

COVID-19 Management in the Pediatric Age: Consensus Document of the COVID-19 Working Group in Paediatrics of the Emilia-Romagna Region (RE-CO-Ped), Italy

Since December 2019, coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly spread, becoming the first pandemic of the 21st century by number of deaths (over 2,000,000 worldwide). Many aspects of SARS-CoV-2 infection in children and adolescents remain unclear, and optimal treatment has not yet been defined. Therefore, our goal was to develop a consensus document, practically synthesizing the accumulated data and clinical experience of our expert group. Literature research was carried out using the keywords "COVID-19" or "SARS-CoV-2" and "children" or "pediatrics" and "prevention" or "diagnosis" or "MIS-C" or "treatment" in electronic databases (MEDLINE, PUBMED), existing guidelines and gray literature. The fact that the majority of the problems posed by SARS-CoV-2 infection in pediatric age do not need hospital care and that, therefore, infected children and adolescents can be managed at home highlights the need for a strengthening of territorial pediatric structures. The sharing of hospitalization and therapeutic management criteria for severe cases between professionals is essential to ensure a fair approach based on the best available knowledge. Moreover, the activity of social and health professionals must also include the description, management and limitation of psychophysical-relational damage resulting from the SARS-CoV-2 pandemic on the health of children and adolescents, whether or not affected by COVID-19. Due to the characteristics of COVID-19 pathology in pediatric age, the importance of strengthening the network between hospital and territorial pediatrics, school, educational, social and family personnel both for strictly clinical management and for the reduction in discomfort, with priority in children of more frail families, represents a priority.

[Strategy for a Risk-stratified Use of Rapid Antigen Testing: Containing the SARS-CoV-2 Pandemic by Integrating Rapid Testing into Case and Contact Tracing Management]

The use of rapid testing offers an opportunity to contain the SARS-CoV-2 pandemic; however, the impact of false-positive and false-negative test results and population response must be anticipated and taken into consideration to avoid or mitigate harm. Untargeted use of rapid testing is associated with high direct and indirect costs and will have limited impact on the pandemic if resources are used inefficiently. We suggest using a risk-stratified testing strategy, based on targeted testing directly integrated with the Public Health Service's case and contact tracing management. According to the proposed targeted testing strategy stratified by risk of infection, all persons with acute symptoms of a respiratory infection as well as other population groups with an elevated probability of being infected with SARS-CoV-2 infection should be specifically tested to identify "hidden" infection networks. The strategy should include a uniform communication strategy for dealing with positive and negative test results, a targeted expansion of access to low-threshold testing opportunities, ensuring timely and free access to the results of confirmatory tests, and integration into an overarching documentation system for evaluation. This integration of a risk-stratified targeted testing strategy into case and contact tracing management embedded in a comprehensive strategy can help to reduce infection rates in a resource-efficient and sustainable manner.

Lumipulse G SARS-CoV-2 Ag assay evaluation using clinical samples from different testing groups

OBJECTIVES

Compared to RT-PCR, lower performance of antigen detection assays, including the Lumipulse G SARS-CoV-2 Ag assay, may depend on specific testing scenarios.

METHODS

We tested 594 nasopharyngeal swab samples from individuals with COVID-19 (RT-PCR cycle threshold [Ct] values ≤ 40) or non-COVID-19 (Ct values >40) diagnoses. RT-PCR positive samples were assigned to diagnostic, screening, or monitoring groups of testing.

RESULTS

With a limit of detection of 1.2 × 10⁴ SARS-CoV-2 RNA copies/mL, Lumipulse showed positive percent agreement (PPA) of 79.9% (155/194) and negative percent agreement of 99.3% (397/400), whereas PPAs were 100% for samples with Ct values of <18 or 18-<25 and 92.5% for samples with Ct values of 25-<30. By three groups, Lumipulse showed PPA of 87.0% (60/69), 81.1% (43/53), or 72.2% (52/72), respectively, whereas PPA was 100% for samples with Ct values of <18 or 18-<25, and was 94.4, 80.0, or 100% for samples with Ct values of 25-<30, respectively. Additional testing of RT-PCR positive samples for SARS-CoV-2 subgenomic RNA showed that, by three groups, PPA was 63.8% (44/69), 62.3% (33/53), or 33.3% (24/72), respectively. PPAs dropped to 55.6, 20.0, or 41.7% for samples with Ct values of 25-<30, respectively. All 101 samples with a subgenomic RNA positive result had a Lumipulse assay's antigen positive result, whereas only 54 (58.1%) of remaining 93 samples had a Lumipulse assay's antigen positive result.

CONCLUSIONS

Lumipulse assay was highly sensitive in samples with low RT-PCR Ct values, implying repeated testing to reduce consequences of false-negative results.

SARS-CoV-2 Diagnostic Tests: Algorithm and Field Evaluation From the Near Patient Testing to the Automated Diagnostic Platform

Introduction: Since the first wave of COVID-19 in Europe, new diagnostic tools using antigen detection and rapid molecular techniques have been developed. Our objective was to elaborate a diagnostic algorithm combining antigen rapid diagnostic tests, automated antigen dosing and rapid molecular tests and to assess its performance under routine conditions. Methods: An analytical performance evaluation of four antigen rapid tests, one automated antigen dosing and one molecular point-of-care test was performed on samples sent to our laboratory for a SARS-CoV-2 reverse transcription PCR. We then established a diagnostic algorithm by approaching median viral loads in target populations and evaluated the limit of detection of each test using the PCR cycle threshold values. A field performance evaluation including a clinical validation and a user-friendliness assessment was then conducted on the antigen rapid tests in point-of-care settings (general practitioners and emergency rooms) for outpatients who were symptomatic for <7 days. Automated antigen dosing was trialed for the screening of asymptomatic inpatients. Results: Our diagnostic algorithm proposed to test recently symptomatic patients using rapid antigen tests, asymptomatic patients using automated tests, and patients requiring immediate admission using molecular point-of-care tests. Accordingly, the conventional reverse transcription PCR was kept as a second line tool. In this setting, antigen rapid tests yielded an overall sensitivity of 83.3% (not significantly different between the four assays) while the use of automated antigen dosing would have spared 93.5% of asymptomatic inpatient screening PCRs. Conclusion: Using tests not considered the "gold standard" for COVID-19 diagnosis on well-defined target populations allowed for the optimization of their intrinsic performances, widening the scale of our testing arsenal while sparing molecular resources for more seriously ill patients.

CovidArray: A Microarray-Based Assay with High Sensitivity for the Detection of Sars-Cov-2 in Nasopharyngeal Swabs

A new coronavirus (SARS-CoV-2) caused the current coronavirus disease (Covid-19) epidemic. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) is used as the gold standard for clinical detection of SARS-CoV-2. Under ideal conditions, RT-qPCR Covid-19 assays have analytical sensitivity and specificity greater than 95%. However, when the sample panel is enlarged including asymptomatic individuals, the sensitivity decreases and false negatives are reported. Moreover, RT-qPCR requires up to 3–6 h with most of the time involved in RNA extraction from swab samples. We introduce CovidArray, a microarray-based assay, to detect SARS-CoV-2 markers N1 and N2 in the nasopharyngeal swabs. The method is based on solid-phase hybridization of fluorescently-labeled amplicons upon RNA extraction and reverse transcription. This approach combines the physical-optical properties of the silicon substrate with the surface chemistry used to coat the substrate to obtain a diagnostic tool of great sensitivity. Furthermore, we used an innovative approach, RNAGEM, to extract and purify viral RNA in less than 15 min. We correctly assigned 12 nasopharyngeal swabs, previously analyzed by RT-qPCR. Thanks to the CovidArray sensitivity we were able to identify a false-negative sample. CovidArray is the first DNA microarray-based assay to detect viral genes in the swabs. Its high sensitivity and the innovative viral RNA extraction by RNAGEM allows the reduction of both the amount of false-negative results and the total analysis time to about 2 h.

Microbiological Testing for Coronavirus Disease 2019

Microbiological diagnosis of coronavirus disease 2019 (COVID-19) is mainly performed through nucleic acid amplification test (NAAT) and antigen test. Although NAAT is the standard diagnostic test, its use is limited by insufficient laboratory resources and long turnaround time. Point-of-care NAAT tests have been introduced to address these shortcomings, but their varied sensitivity and resource constraints remain a concern. Antigen tests require fewer resources but have low sensitivity. Nevertheless, low-sensitivity tests may be useful depending on the situation. In contrast, in some clinical phases of COVID-19, high-sensitivity tests may provide false-negative results. Therefore, the right testing strategy is needed for an accurate diagnosis. In this review, the characteristics and clinical applications of microbiological tests available in Japan (NAAT, antigen test, and antibody test) are discussed. The clinical diagnosis of COVID-19 is slightly complicated, and cases in which the infection spreads from asymptomatic infected individuals are many; hence, laboratory diagnosis is essential to prevent further transmission.

Performances of the VitaPCR™ SARS-CoV-2 Assay during the second wave of the COVID-19 epidemic in France

To assess the practicability (usability and satisfaction) and analytical performances of the VitaPCR™ SARS‐CoV‐2 Assay (Credo Diagnostics Biomedical Pte. Ltd.), a rapid point‐of‐care nucleic acid amplification test (NAAT), by reference to real‐time reverse‐transcription polymerase chain reaction (rRT‐PCR) for respiratory viruses. The practicability of the VitaPCR™ Assay and Instrument was assessed from usability evaluation and a satisfaction questionnaire. Nasopharyngeal swabs were collected from 239 patients with coronavirus disease 2019 (COVID‐19)‐like illness during the second epidemic wave, in Paris, France. Overall, the usability of the VitaPCR™ Instrument was high. The satisfaction questionnaire indicated a high appreciation of the VitaPCR™ NAAT mainly for the short duration of analysis in only 20 min. A total of 140 and 99 samples were positive and negative for SARS‐CoV‐2 RNA by rRT‐PCR, respectively. In the event of significant viral load (i.e., N gene C_t values  33), the platform's analytical performances dropped significantly, with lower sensitivity, concordance, and accuracy, while its specificity remained high. The VitaPCR™ SARS‐CoV‐2 Assay is an accurate rapid point‐of‐care NAAT, suitable for clinical practice for the rapid diagnosis of COVID‐19, especially in patients with COVID‐19‐suspected symptoms.

The Inclusive Review on SARS-CoV-2 Biology, Epidemiology, Diagnosis, and Potential Management Options

A novel coronavirus member was reported in Wuhan City, Hubei Province, China, at the end of the year 2019. Initially, the infection spread locally, affecting the Wuhan people, and then expanded rapidly throughout the world. On 11 March 2020, the World Health Organization (WHO) proclaimed it a global pandemic. The virus is a new strain most closely related to a bat coronavirus (RaTG13) which was not previously discovered in humans and is now formally known as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Coronavirus disease 2019 (COVID-19) is the disease syndrome that the SARS-CoV-2 virus triggers. It is suggested that SARS-CoV-2 can be transmitted through aerosols, direct/indirect contact, and also during medical procedures and specimen handling. The infection is characterized by isolated flu-like symptoms, but there may be specific signs of fever, fatigue, cough, and shortness of breath, as well as the loss of smell and breathing difficulty. Within this report, we tried to review the most current scientific literature published by January 2021 on various aspects of the outbreak, including virus structure, pathogenesis, clinical presentation, epidemiology, diagnostic approaches, potential therapeutics and vaccines, and prospects. We hope this article makes a beneficial impact on public education to better deal with the SARS-CoV-2 crisis and push a step forward in the near term towards its prevention and control.

Smart testing and selective quarantine for the control of epidemics

This paper is based on the observation that, during Covid-19 epidemic, the choice of which individuals should be tested has an important impact on the effectiveness of selective confinement measures. This decision problem is closely related to the problem of optimal sensor selection, which is a very active research subject in control engineering. The goal of this paper is to propose a policy to smartly select the individuals to be tested. The main idea is to model the epidemics as a stochastic dynamic system and to select the individual to be tested accordingly to some optimality criteria, e.g. to minimize the probability of undetected asymptomatic cases. Every day, the probability of infection of the different individuals is updated making use of the stochastic model of the phenomenon and of the information collected in the previous days. Simulations for a closed community of 10'000 individuals show that the proposed technique, coupled with a selective confinement policy, can reduce the spread of the disease while limiting the number of individuals confined if compared to the simple contact tracing of positive and to an off-line test selection strategy based on the number of contacts.

Rapid, point-of-care antigen and molecular-based tests for diagnosis of SARS-CoV-2 infection

BACKGROUND

Accurate rapid diagnostic tests for SARS-CoV-2 infection could contribute to clinical and public health strategies to manage the COVID-19 pandemic. Point-of-care antigen and molecular tests to detect current infection could increase access to testing and early confirmation of cases, and expediate clinical and public health management decisions that may reduce transmission.

OBJECTIVES

To assess the diagnostic accuracy of point-of-care antigen and molecular-based tests for diagnosis of SARS-CoV-2 infection. We consider accuracy separately in symptomatic and asymptomatic population groups.

SEARCH METHODS

Electronic searches of the Cochrane COVID-19 Study Register and the COVID-19 Living Evidence Database from the University of Bern (which includes daily updates from PubMed and Embase and preprints from medRxiv and bioRxiv) were undertaken on 30 Sept 2020. We checked repositories of COVID-19 publications and included independent evaluations from national reference laboratories, the Foundation for Innovative New Diagnostics and the Diagnostics Global Health website to 16 Nov 2020. We did not apply language restrictions.

SELECTION CRITERIA

We included studies of people with either suspected SARS-CoV-2 infection, known SARS-CoV-2 infection or known absence of infection, or those who were being screened for infection. We included test accuracy studies of any design that evaluated commercially produced, rapid antigen or molecular tests suitable for a point-of-care setting (minimal equipment, sample preparation, and biosafety requirements, with results within two hours of sample collection). We included all reference standards that define the presence or absence of SARS-CoV-2 (including reverse transcription polymerase chain reaction (RT-PCR) tests and established diagnostic criteria).

DATA COLLECTION AND ANALYSIS

Studies were screened independently in duplicate with disagreements resolved by discussion with a third author. Study characteristics were extracted by one author and checked by a second; extraction of study results and assessments of risk of bias and applicability (made using the QUADAS-2 tool) were undertaken independently in duplicate. We present sensitivity and specificity with 95% confidence intervals (CIs) for each test and pooled data using the bivariate model separately for antigen and molecular-based tests. We tabulated results by test manufacturer and compliance with manufacturer instructions for use and according to symptom status.

MAIN RESULTS

Seventy-eight study cohorts were included (described in 64 study reports, including 20 pre-prints), reporting results for 24,087 samples (7,415 with confirmed SARS-CoV-2). Studies were mainly from Europe (n = 39) or North America (n = 20), and evaluated 16 antigen and five molecular assays. We considered risk of bias to be high in 29 (50%) studies because of participant selection; in 66 (85%) because of weaknesses in the reference standard for absence of infection; and in 29 (45%) for participant flow and timing. Studies of antigen tests were of a higher methodological quality compared to studies of molecular tests, particularly regarding the risk of bias for participant selection and the index test. Characteristics of participants in 35 (45%) studies differed from those in whom the test was intended to be used and the delivery of the index test in 39 (50%) studies differed from the way in which the test was intended to be used. Nearly all studies (97%) defined the presence or absence of SARS-CoV-2 based on a single RT-PCR result, and none included participants meeting case definitions for probable COVID-19. Antigen tests Forty-eight studies reported 58 evaluations of antigen tests. Estimates of sensitivity varied considerably between studies. There were differences between symptomatic (72.0%, 95% CI 63.7% to 79.0%; 37 evaluations; 15530 samples, 4410 cases) and asymptomatic participants (58.1%, 95% CI 40.2% to 74.1%; 12 evaluations; 1581 samples, 295 cases). Average sensitivity was higher in the first week after symptom onset (78.3%, 95% CI 71.1% to 84.1%; 26 evaluations; 5769 samples, 2320 cases) than in the second week of symptoms (51.0%, 95% CI 40.8% to 61.0%; 22 evaluations; 935 samples, 692 cases). Sensitivity was high in those with cycle threshold (Ct) values on PCR ≤25 (94.5%, 95% CI 91.0% to 96.7%; 36 evaluations; 2613 cases) compared to those with Ct values >25 (40.7%, 95% CI 31.8% to 50.3%; 36 evaluations; 2632 cases). Sensitivity varied between brands. Using data from instructions for use (IFU) compliant evaluations in symptomatic participants, summary sensitivities ranged from 34.1% (95% CI 29.7% to 38.8%; Coris Bioconcept) to 88.1% (95% CI 84.2% to 91.1%; SD Biosensor STANDARD Q). Average specificities were high in symptomatic and asymptomatic participants, and for most brands (overall summary specificity 99.6%, 95% CI 99.0% to 99.8%). At 5% prevalence using data for the most sensitive assays in symptomatic people (SD Biosensor STANDARD Q and Abbott Panbio), positive predictive values (PPVs) of 84% to 90% mean that between 1 in 10 and 1 in 6 positive results will be a false positive, and between 1 in 4 and 1 in 8 cases will be missed. At 0.5% prevalence applying the same tests in asymptomatic people would result in PPVs of 11% to 28% meaning that between 7 in 10 and 9 in 10 positive results will be false positives, and between 1 in 2 and 1 in 3 cases will be missed. No studies assessed the accuracy of repeated lateral flow testing or self-testing. Rapid molecular assays Thirty studies reported 33 evaluations of five different rapid molecular tests. Sensitivities varied according to test brand. Most of the data relate to the ID NOW and Xpert Xpress assays. Using data from evaluations following the manufacturer's instructions for use, the average sensitivity of ID NOW was 73.0% (95% CI 66.8% to 78.4%) and average specificity 99.7% (95% CI 98.7% to 99.9%; 4 evaluations; 812 samples, 222 cases). For Xpert Xpress, the average sensitivity was 100% (95% CI 88.1% to 100%) and average specificity 97.2% (95% CI 89.4% to 99.3%; 2 evaluations; 100 samples, 29 cases). Insufficient data were available to investigate the effect of symptom status or time after symptom onset.

AUTHORS' CONCLUSIONS

Antigen tests vary in sensitivity. In people with signs and symptoms of COVID-19, sensitivities are highest in the first week of illness when viral loads are higher. The assays shown to meet appropriate criteria, such as WHO's priority target product profiles for COVID-19 diagnostics ('acceptable' sensitivity ≥ 80% and specificity ≥ 97%), can be considered as a replacement for laboratory-based RT-PCR when immediate decisions about patient care must be made, or where RT-PCR cannot be delivered in a timely manner. Positive predictive values suggest that confirmatory testing of those with positive results may be considered in low prevalence settings. Due to the variable sensitivity of antigen tests, people who test negative may still be infected. Evidence for testing in asymptomatic cohorts was limited. Test accuracy studies cannot adequately assess the ability of antigen tests to differentiate those who are infectious and require isolation from those who pose no risk, as there is no reference standard for infectiousness. A small number of molecular tests showed high accuracy and may be suitable alternatives to RT-PCR. However, further evaluations of the tests in settings as they are intended to be used are required to fully establish performance in practice. Several important studies in asymptomatic individuals have been reported since the close of our search and will be incorporated at the next update of this review. Comparative studies of antigen tests in their intended use settings and according to test operator (including self-testing) are required.

Performance Characteristics of BinaxNOW COVID-19 Antigen Card for Screening Asymptomatic Individuals in a University Setting

We compared the performance of the Abbott BinaxNOW COVID-19 antigen card to that of a standard reverse transcription-PCR (RT-PCR) assay (Thermo Fisher TaqPath COVID-19 Combo kit) for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2,645 asymptomatic students presenting for screening at the University of Utah. SARS-CoV-2 RNA was detected in 1.7% of the study participants by RT-PCR.

We compared the performance of the Abbott BinaxNOW COVID-19 antigen card to that of a standard reverse transcription-PCR (RT-PCR) assay (Thermo Fisher TaqPath COVID-19 Combo kit) for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2,645 asymptomatic students presenting for screening at the University of Utah. SARS-CoV-2 RNA was detected in 1.7% of the study participants by RT-PCR. BinaxNOW identified 24 infections but missed 21 infections that were detected by RT-PCR. The analytical sensitivity (positive agreement) and analytical specificity (negative agreement) for the BinaxNOW were 53.3% and 100%, respectively, compared to the RT-PCR assay. The median cycle threshold (C_T) value in the specimens that had concordant positive BinaxNOW antigen results was significantly lower than that of specimens that were discordant (C_T of 17.6 versus 29.6; P < 0.001). In individuals with presumably high viral loads (C_T of <23.0), a 95.8% positive agreement was observed between the RT-PCR assay and BinaxNOW. Due to the possibility of false-negative results, caution must be taken when utilizing rapid antigen testing for screening asymptomatic individuals.

A review on current diagnostic techniques for COVID-19

INTRODUCTION

SARS-Cov-2 first appeared in Wuhan, China, in December 2019 and spread all over the world soon after that. Given the infectious nature ofSARS-CoV-2, fast and accurate diagnosis tools are important to detect the virus. In this review, we discuss the different diagnostic tests that are currently being implemented in laboratories and provide a description of various COVID-19 kits.

AREAS COVERED

We summarize molecular techniques that target the viral load, serological methods used for SARS-CoV-2 specific antibodies detection as well as newly developed faster assays for the detection of SARS-COV 2 in various biological samples.

EXPERT OPINION

In the light of the widespread pandemic, the massive diagnosis of COVID-19, using various detection techniques, appears to be the most effective strategy for monitoring and containing its propagation.

Surveillance of Acute SARS-CoV-2 Infections in School Children and Point-Prevalence During a Time of High Community Transmission in Switzerland

Background: Switzerland had one of the highest incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in Europe during the second wave. Schools were open as in most of Europe with specific preventive measures in place. However, the frequency and transmission of acute unrecognized, asymptomatic or oligosymptomatic infections in schools during this time of high community transmission is unknown. Thereof, our aim was to pilot a surveillance system that detects acute SARS-CoV-2 infections in schools and possible transmission within classes. Methods: Fourteen out of the randomly selected sample of the Ciao Corona cohort study participated between December 1 and 11, a time when incidence rate for SARS-CoV-2 infections was high for the canton of Zurich. We determined point-prevalence of acute SARS-CoV-2 infections of school children attending primary and secondary school. A buccal swab for polymerase chain reaction (PCR) and a rapid diagnostic test (RDT) to detect SARS-CoV-2 were taken twice 1 week apart (T1 and T2) in a cohort of children from randomly selected classes. A questionnaire assessed demographics and symptoms compatible with a SARS-CoV-2 infection during the past 5 days. Results: Out of 1,299 invited children, 641 (49%) 6- to 16-year-old children and 66 teachers from 14 schools and 67 classes participated in at least one of two testings. None of the teachers but one child had a positive PCR at T1, corresponding to a point-prevalence in children of 0.2% (95% CI 0.0-1.1%), and no positive PCR was detected at T2. The child with positive PCR at T1 was negative on the RDT at T1 and both tests were negative at T2. There were 7 (0.6%) false positive RDTs in children and 2 (1.7%) false positive RDTs in teachers at T1 or T2 among 5 schools (overall prevalence 0.7%). All 9 initially positive RDTs were negative in a new buccal sample taken 2 h to 2 days later, also confirmed by PCR. Thirty-five percent of children and 8% of teachers reported mild symptoms during the 5 days prior to testing. Conclusion: In a setting of high incidence of SARS-CoV-2 infections, unrecognized virus spread within schools was very low. Schools appear to be safe with the protective measures in place (e.g., clearly symptomatic children have to stay at home, prompt contact tracing with individual and class-level quarantine, and structured infection prevention measures in school). Specificity of the RDT was within the lower boundary of performance and needs further evaluation for its use in schools. Given the low point prevalence even in a setting of very high incidence, a targeted test, track, isolate and quarantine (TTIQ) strategy for symptomatic children and school personnel adapted to school settings is likely more suitable approach than surveillance on entire classes and schools. Clinical Trial Registration: https://clinicaltrials.gov/ct2/show/NCT04448717, ClinicalTrials.gov NCT04448717.

Thoracic imaging tests for the diagnosis of COVID-19

BACKGROUND

The respiratory illness caused by SARS-CoV-2 infection continues to present diagnostic challenges. Our 2020 edition of this review showed thoracic (chest) imaging to be sensitive and moderately specific in the diagnosis of coronavirus disease 2019 (COVID-19). In this update, we include new relevant studies, and have removed studies with case-control designs, and those not intended to be diagnostic test accuracy studies.

OBJECTIVES

To evaluate the diagnostic accuracy of thoracic imaging (computed tomography (CT), X-ray and ultrasound) in people with suspected COVID-19.

SEARCH METHODS

We searched the COVID-19 Living Evidence Database from the University of Bern, the Cochrane COVID-19 Study Register, The Stephen B. Thacker CDC Library, and repositories of COVID-19 publications through to 30 September 2020. We did not apply any language restrictions.

SELECTION CRITERIA

We included studies of all designs, except for case-control, that recruited participants of any age group suspected to have COVID-19 and that reported estimates of test accuracy or provided data from which we could compute estimates.

DATA COLLECTION AND ANALYSIS

The review authors independently and in duplicate screened articles, extracted data and assessed risk of bias and applicability concerns using the QUADAS-2 domain-list. We presented the results of estimated sensitivity and specificity using paired forest plots, and we summarised pooled estimates in tables. We used a bivariate meta-analysis model where appropriate. We presented the uncertainty of accuracy estimates using 95% confidence intervals (CIs).

MAIN RESULTS

We included 51 studies with 19,775 participants suspected of having COVID-19, of whom 10,155 (51%) had a final diagnosis of COVID-19. Forty-seven studies evaluated one imaging modality each, and four studies evaluated two imaging modalities each. All studies used RT-PCR as the reference standard for the diagnosis of COVID-19, with 47 studies using only RT-PCR and four studies using a combination of RT-PCR and other criteria (such as clinical signs, imaging tests, positive contacts, and follow-up phone calls) as the reference standard. Studies were conducted in Europe (33), Asia (13), North America (3) and South America (2); including only adults (26), all ages (21), children only (1), adults over 70 years (1), and unclear (2); in inpatients (2), outpatients (32), and setting unclear (17). Risk of bias was high or unclear in thirty-two (63%) studies with respect to participant selection, 40 (78%) studies with respect to reference standard, 30 (59%) studies with respect to index test, and 24 (47%) studies with respect to participant flow. For chest CT (41 studies, 16,133 participants, 8110 (50%) cases), the sensitivity ranged from 56.3% to 100%, and specificity ranged from 25.4% to 97.4%. The pooled sensitivity of chest CT was 87.9% (95% CI 84.6 to 90.6) and the pooled specificity was 80.0% (95% CI 74.9 to 84.3). There was no statistical evidence indicating that reference standard conduct and definition for index test positivity were sources of heterogeneity for CT studies. Nine chest CT studies (2807 participants, 1139 (41%) cases) used the COVID-19 Reporting and Data System (CO-RADS) scoring system, which has five thresholds to define index test positivity. At a CO-RADS threshold of 5 (7 studies), the sensitivity ranged from 41.5% to 77.9% and the pooled sensitivity was 67.0% (95% CI 56.4 to 76.2); the specificity ranged from 83.5% to 96.2%; and the pooled specificity was 91.3% (95% CI 87.6 to 94.0). At a CO-RADS threshold of 4 (7 studies), the sensitivity ranged from 56.3% to 92.9% and the pooled sensitivity was 83.5% (95% CI 74.4 to 89.7); the specificity ranged from 77.2% to 90.4% and the pooled specificity was 83.6% (95% CI 80.5 to 86.4). For chest X-ray (9 studies, 3694 participants, 2111 (57%) cases) the sensitivity ranged from 51.9% to 94.4% and specificity ranged from 40.4% to 88.9%. The pooled sensitivity of chest X-ray was 80.6% (95% CI 69.1 to 88.6) and the pooled specificity was 71.5% (95% CI 59.8 to 80.8). For ultrasound of the lungs (5 studies, 446 participants, 211 (47%) cases) the sensitivity ranged from 68.2% to 96.8% and specificity ranged from 21.3% to 78.9%. The pooled sensitivity of ultrasound was 86.4% (95% CI 72.7 to 93.9) and the pooled specificity was 54.6% (95% CI 35.3 to 72.6). Based on an indirect comparison using all included studies, chest CT had a higher specificity than ultrasound. For indirect comparisons of chest CT and chest X-ray, or chest X-ray and ultrasound, the data did not show differences in specificity or sensitivity.

AUTHORS' CONCLUSIONS

Our findings indicate that chest CT is sensitive and moderately specific for the diagnosis of COVID-19. Chest X-ray is moderately sensitive and moderately specific for the diagnosis of COVID-19. Ultrasound is sensitive but not specific for the diagnosis of COVID-19. Thus, chest CT and ultrasound may have more utility for excluding COVID-19 than for differentiating SARS-CoV-2 infection from other causes of respiratory illness. Future diagnostic accuracy studies should pre-define positive imaging findings, include direct comparisons of the various modalities of interest in the same participant population, and implement improved reporting practices.

Clinical Evaluation of Roche SD Biosensor Rapid Antigen Test for SARS-CoV-2 in Municipal Health Service Testing Site, the Netherlands

Rapid detection of infection is essential for stopping the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The Roche SD Biosensor rapid antigen test for SARS-CoV-2 was evaluated in a nonhospitalized symptomatic population. We rapid-tested a sample onsite and compared results with those from reverse transcription PCR and virus culture. We analyzed date of onset and symptoms using data from a clinical questionnaire. Overall test sensitivity was 84.9% (95% CI 79.1–89.4) and specificity was 99.5% (95% CI 98.7–99.8). Sensitivity increased to 95.8% (95% CI 90.5–98.2) for persons who sought care within 7 days of symptom onset. Test band intensity and time to result correlated strongly with viral load; thus, strong positive results could be read before the recommended time. Approximately 98% of all viable specimens with cycle threshold <30 were detected. Rapid antigen tests can detect symptomatic SARS-CoV-2 infections in the early phase of disease, thereby identifying the most infectious persons.

Diagnostic Utility of a Ferritin-to-Procalcitonin Ratio to Differentiate Patients With COVID-19 From Those With Bacterial Pneumonia: A Multicenter Study

Background

There is an urgent need for accurate, rapid, inexpensive biomarkers that can differentiate coronavirus disease 2019 (COVID-19) from bacterial pneumonia. We assess the role of the ferritin-to-procalcitonin (F/P) ratio to classify pneumonia cases into those due to COVID-19 vs those due to bacterial pathogens.

Methods

This multicenter case–control study compared patients with COVID-19 with those with bacterial pneumonia, admitted between March 1 and May 31, 2020. Patients with COVID-19 and bacterial pneumonia co-infection were excluded. The F/P in patients with COVID-19 vs with bacterial pneumonia were compared. Receiver operating characteristic curve analysis determined the sensitivity and specificity of various cutoff F/P values for COVID-19 vs bacterial pneumonia.

Results

A total of 242 COVID-19 pneumonia cases and 34 bacterial pneumonia controls were included. Patients with COVID-19 pneumonia had a lower mean age (57.1 vs 64.4 years; P = .02) and a higher body mass index (30.74 vs 27.15 kg/m²; P = .02) compared with patients with bacterial pneumonia. Cases and controls had a similar proportion of women (47% vs 53%; P = .5), and COVID-19 patients had a higher prevalence of diabetes mellitus (32.6% vs 12%; P = .01). The median F/P was significantly higher in patients with COVID-19 (4037.5) compared with the F/P in bacterial pneumonia (802; P < .001). An F/P ≥877, used to diagnose COVID-19, resulted in a sensitivity of 85% and a specificity of 56%, with a positive predictive value of 93.2% and a likelihood ratio of 1.92. In multivariable analyses, an F/P ≥877 was associated with greater odds of identifying a COVID-19 case (odds ratio, 11.27; 95% CI, 4–31.2; P < .001).

Conclusions

An F/P ≥877 increases the likelihood of COVID-19 pneumonia compared with bacterial pneumonia.

Clinical prediction rule for SARS-CoV-2 infection from 116 U.S. emergency departments 2-22-2021

Objectives

Accurate and reliable criteria to rapidly estimate the probability of infection with the novel coronavirus-2 that causes the severe acute respiratory syndrome (SARS-CoV-2) and associated disease (COVID-19) remain an urgent unmet need, especially in emergency care. The objective was to derive and validate a clinical prediction score for SARS-CoV-2 infection that uses simple criteria widely available at the point of care.

Methods

Data came from the registry data from the national REgistry of suspected COVID-19 in EmeRgency care (RECOVER network) comprising 116 hospitals from 25 states in the US. Clinical variables and 30-day outcomes were abstracted from medical records of 19,850 emergency department (ED) patients tested for SARS-CoV-2. The criterion standard for diagnosis of SARS-CoV-2 required a positive molecular test from a swabbed sample or positive antibody testing within 30 days. The prediction score was derived from a 50% random sample (n = 9,925) using unadjusted analysis of 107 candidate variables as a screening step, followed by stepwise forward logistic regression on 72 variables.

Results

Multivariable regression yielded a 13-variable score, which was simplified to a 13-point score: +1 point each for age>50 years, measured temperature>37.5°C, oxygen saturation<95%, Black race, Hispanic or Latino ethnicity, household contact with known or suspected COVID-19, patient reported history of dry cough, anosmia/dysgeusia, myalgias or fever; and -1 point each for White race, no direct contact with infected person, or smoking. In the validation sample (n = 9,975), the probability from logistic regression score produced an area under the receiver operating characteristic curve of 0.80 (95% CI: 0.79–0.81), and this level of accuracy was retained across patients enrolled from the early spring to summer of 2020. In the simplified score, a score of zero produced a sensitivity of 95.6% (94.8–96.3%), specificity of 20.0% (19.0–21.0%), negative likelihood ratio of 0.22 (0.19–0.26). Increasing points on the simplified score predicted higher probability of infection (e.g., >75% probability with +5 or more points).

Conclusion

Criteria that are available at the point of care can accurately predict the probability of SARS-CoV-2 infection. These criteria could assist with decisions about isolation and testing at high throughput checkpoints.

Quantifying the potential value of antigen-detection rapid diagnostic tests for COVID-19: a modelling analysis

BACKGROUND

Testing plays a critical role in treatment and prevention responses to the COVID-19 pandemic. Compared to nucleic acid tests (NATs), antigen-detection rapid diagnostic tests (Ag-RDTs) can be more accessible, but typically have lower sensitivity and specificity. By quantifying these trade-offs, we aimed to inform decisions about when an Ag-RDT would offer greater public health value than reliance on NAT.

METHODS

Following an expert consultation, we selected two use cases for analysis: rapid identification of people with COVID-19 amongst patients admitted with respiratory symptoms in a 'hospital' setting and early identification and isolation of people with mildly symptomatic COVID-19 in a 'community' setting. Using decision analysis, we evaluated the health system cost and health impact (deaths averted and infectious days isolated) of an Ag-RDT-led strategy, compared to a strategy based on NAT and clinical judgement. We adopted a broad range of values for 'contextual' parameters relevant to a range of settings, including the availability of NAT and the performance of clinical judgement. We performed a multivariate sensitivity analysis to all of these parameters.

RESULTS

In a hospital setting, an Ag-RDT-led strategy would avert more deaths than a NAT-based strategy, and at lower cost per death averted, when the sensitivity of clinical judgement is less than 90%, and when NAT results are available in time to inform clinical decision-making for less than 85% of patients. The use of an Ag-RDT is robustly supported in community settings, where it would avert more transmission at lower cost than relying on NAT alone, under a wide range of assumptions.

CONCLUSIONS

Despite their imperfect sensitivity and specificity, Ag-RDTs have the potential to be simultaneously more impactful, and have a lower cost per death and infectious person-days averted, than current approaches to COVID-19 diagnostic testing.