ABSTRACT
Clinical trials of SARS-CoV-2 therapeutics often include virological secondary endpoints to compare viral clearance and viral load reduction between treatment and placebo arms. This is typically achieved using RT-qPCR, which cannot differentiate replicant competent virus from non-viable virus or free RNA, limiting its utility as an endpoint. Culture based methods for SARS-CoV-2 exist; however, these are often insensitive and poorly standardised for use as clinical trial endpoints. We report optimisation of a culture-based approach evaluating three cell lines, three detection methods, and key culture parameters. We show that Vero-ACE2-TMPRSS2 (VAT) cells in combination with RT-qPCR of culture supernatants from the first passage provides the greatest overall detection of Delta viral replication (22/32, 68.8%), being able to identify viable virus in 83.3% (20/24) of clinical samples with initial Ct values <30. Likewise, we demonstrate that RT-qPCR using culture supernatants from the first passage of Vero hSLAM cells provides the highest overall detection of Omicron viral replication (9/31, 29%), detecting live virus in 39.1% (9/23) of clinical samples with initial Ct values < 25. This assessment demonstrates that combining RT-qPCR with virological end point analysis has utility in clinical trials of therapeutics for SARS-CoV-2; however, techniques may require optimising based on dominant circulating strain.
ABSTRACT
Background The continued emergence of SARS-CoV-2 variants of concern (VOC) requires timely analytical and clinical evaluation of antigen-based rapid diagnostic tests (Ag-RDTs) especially those that are recommended for at home use. Methods The limit of detection (LOD) of 34 Ag-RDTs was evaluated using the most encountered SARS-CoV-2 VOC viral isolates (Alpha, Delta, Gamma, Omicron BA.1, Omicron BA.5) and the wild type (WT). Clinical sensitivity was further evaluated for five Ag-RDT utilising retrospective samples (Alpha, Delta, Omicron BA.1) and one Ag-RDT utilising prospective clinical samples (Delta and Omicron BA.1). Findings For the WT, Alpha, Delta, Gamma and Omicron (BA.1) variants 22, 32, 29, 31 and 32 of the 34 Ag-RDTs evaluated met the World Health Organisations (WHO) target product profile (TPP), respectively. Of the 31 Ag-RDTs included for Omicron BA.5 evaluation 29 met the WHO TPP. Additionally, the LODs for samples spiked with Omicron BA.5 were significantly lower than all other VOCs included (p<0.001). In the retrospective clinical evaluation when comparing RNA copies/mL, the Ag-RDTs detected Alpha and Omicron (BA.1) more sensitively than the Delta VOC. Samples with high RT-qPCR Cts (Ct>25) resulted in reduced test sensitivities across all variants. We used linear regression to model the 50% and 95% LOD of clinical samples and observed statistically similar results for all tests. In the prospective clinical samples, the sensitivity was statistically similar for the Delta VOC 71.9% (CI 95% 53.3-86.6%) and Omicron VOC 84.4% (CI95% 75.3-91.2%). Interpretation Test performance differs between SARS-CoV-2 VOCs, and high sensitivity was achieved when testing the Omicron BA.5 VOC compared to the WHO Ag-RDT requirements. Continuous evaluations must be performed to monitor test performance.
Subject(s)
COVID-19 , Severe Acute Respiratory SyndromeABSTRACT
The COVID-19 pandemic has given rise to numerous commercially available antigen rapid diagnostic tests (Ag-RDTs). To generate and share accurate and independent data with the global community, multi-site prospective diagnostic evaluations of Ag-RDTs are required. This report describes the clinical evaluation of OnSite COVID-19 Rapid Test (CTK Biotech, California, USA) in Brazil and The United Kingdom. A total of 496 paired nasopharyngeal (NP) swabs were collected from symptomatic healthcare workers at Hospital das Clinicas in Sao Paulo, and 211 NP swabs were collected from symptomatic participants at a COVID-19 drive-through testing site in Liverpool, England. These swabs were analysed by Ag-RDT and results were compared to RT-qPCR. The overall clinical sensitivity of the OnSite COVID-19 Rapid test was 79.6% [95% Cl 70.8 - 86.8%] and specificity was 98.5% [95% Cl 97.2 - 99.3%]. Analytical evaluation of the Ag-RDT was assessed using direct culture supernatant of SARS-CoV-2 strains from Wild-Type (WT), Alpha, Delta, Gamma and Omicron lineages. Analytical limit of detection was 1.0x103 pfu/mL, 1.0x103 pfu/mL, 1.0x102 pfu/mL, 5.0x103 pfu/mL and 1.0x103 pfu/mL, giving a viral copy equivalent of approximately 2.1x105 copies/mL, 2.1x104 copies/mL, 1.6x104 copies/mL, 3.5x106 copies/mL and 8.7 x 104 for the Ag-RDT, when tested on the WT, Alpha, Delta, Gamma and Omicron lineages, respectively. Overall, the OnSite Ag-RDT demonstrates a lower clinical sensitivity than claimed by the manufacturers and narrowly missed out on the World Health Organization's minimum performance requirements for sensitivity of Ag-RDTs targeted to SARS-CoV-2. This study provides comparative performance of an Ag-RDT across two different settings, geographical areas, and population.
Subject(s)
COVID-19ABSTRACT
Objective: To conduct a head-to-head diagnostic accuracy evaluation of professionally taken anterior nares (AN) and nasopharyngeal (NP) swabs for SARS-CoV-2 antigen detection using rapid diagnostic tests (Ag-RDT). Methods: NP swabs for SARS-CoV-2 reverse transcription quantitative polymerase chain reaction (RT-qPCR) testing and paired AN and NP swabs for the antigen detection were collected from symptomatic participants enrolled at a community drive-through COVID-19 test centre in Liverpool. Two Ag-RDT brands were evaluated: Sure-Status (PMC, India) and Biocredit (RapiGEN, South Korea). The visual read out of the Ag-RDT test band was quantitative scored and the 50% and 95% limit of detection (LoD) of both Ag-RDT brands using AN and NP swabs was calculated using a probabilistic logistic regression model. Results: A total of 604 participants were recruited of which 241 (40.3%) were SARS-CoV-2 positive by RT-qPCR. Sensitivity and specificity of AN swabs was equivalent to the obtained with NP swabs: 83.2% (75.2-89.4%) and 98.8% (96.5-99.6%) utilising NP swabs and 84.0% (76.2-90.1%) and 99.2% (97.0-99.8%) with AN swabs for Sure-Status and; 81.2% (73.1-87.7%) and 99.0% (94.7-86.5%) with NP swabs and 79.5% (71.3-86.3%) and 100% (96.5-100%) with AN swabs for Biocredit. The agreement of the AN and NP swabs was high for both brands with an inter-rater relatability (K) of 0.918 and 0.833 for Sure-Status and Biocredit, respectively. The overall 50% LoD and 95% LoD was 0.9-2.4 x 104 and 3.0-3.2 x 108 RNA copies/mL for NP swabs and 0.3- 1.1 x 105 and 0.7-7.9 x 107 RNA copies/mL and for AN swabs with no significant difference on LoD for any of the swabs types or test brands. Quantitative read-out of test line intensity was more often higher when using NP swabs with significantly higher scores for both Ag-RDT brands. Conclusions: the diagnostic accuracy of the two SARS-CoV-2 Ag-RDTs brands evaluated in this study was equivalent using AN swabs than NP swabs. However, test line intensity was lower when using AN swabs which could influence negatively the interpretation of the Ag-RDT results for lay users. Studies on Ag-RDT self-interpretation using AN and NP swabs are needed to ensure accurate test use in the wider community.
Subject(s)
COVID-19ABSTRACT
ObjectivesTo compare self-taken and healthcare worker (HCW)-taken throat/nasal swabs to perform rapid diagnostic tests (RDT) for SARS-CoV-2, and how these compare to RT-PCR. We hypothesised that self-taken samples are non-inferior for use with RDTs and in clinical and research settings could have substantial individual and public health benefit. DesignA prospective diagnostic accuracy evaluation as part of the Facilitating Accelerated Clinical Evaluation of Novel Diagnostic Tests for COVID -19 (FALCON C-19), workstream C (undifferentiated community testing). SettingNHS Test and Trace drive-through community PCR testing site (Liverpool, UK). Participants Eligible participants 18 years or older with symptoms of COVID-19. 250 participants recruited; one withdrew before analysis. SamplingSelf-administered throat/nasal swab for the Covios(R) RDT, a trained HCW taken throat/nasal sample for PCR and HCW comparison throat/nasal swab for RDT. Main outcome measuresSensitivity, specificity, and positive and negative predictive values (PPV, NPV) were calculated; comparisons between self-taken and HCW-taken samples used McNemars test. ResultsSeventy-five participants (75/249, 30.1%) were positive by RT-PCR. RDTs with self-taken swabs had a sensitivity of 90.5% (67/74, 95% CI: 83.9-97.2), compared to 78.4% (58/74, 95% CI: 69.0-87.8) for HCW-taken swabs (absolute difference 12.2%, 95% CI: 4.7-19.6, p=0.003). Specificity for self-taken swabs was 99.4% (173/174, 95% CI: 98.3-100.0), versus 98.9% (172/174, 95% CI: 97.3-100.0) for HCW-taken swabs (absolute difference 0.6%, 95% CI: 0.5-1.7, p=0.317). The PPV of self-taken RDTs (98.5%, 67/68, 95% CI: 95.7-100.0) and HCW-taken RDTs (96.7%, 58/60, 95% CI 92.1-100.0) were not significantly different (p=0.262). However, the NPV of self-taken swab RDTs was significantly higher (96.1%, 173/180, 95% CI: 93.2-98.9) than HCW-taken RDTs (91.5%, 172/188, 95% CI 87.5-95.5, p=0.003). ConclusionSelf-taken swabs for COVID-19 testing offer substantial individual benefits in terms of convenience, accuracy, and reduced risk of transmitting infection. Our results demonstrate that self-taken throat/nasal samples can be used by lay individuals as part of rapid testing programmes for symptomatic adults. Trial RegistrationIRAS ID:28422, clinical trial ID: NCT04408170 SummaryO_ST_ABSWhat is already known on this topic?C_ST_ABSO_LIRapid diagnostic tests (RDTs)for SARS-CoV-2 Ag are a cheaper point-of-care alternative to RT-PCR for diagnosing COVID-19 disease. C_LIO_LIThe accuracy of tests can vary dependent on sampling technique, test processing and reading of results. C_LI What this study adds?O_LISelf-taken throat-nasal swabs for RDTs can be used by symptomatic adults to give reliable results to diagnose SARS-CoV-2. C_LIO_LISelf-sampling can be implemented with little training and no assistance. C_LI
Subject(s)
COVID-19 , CarcinomaABSTRACT
Introduction Successful adoption of POCTs (Point-of-Care tests) for COVID-19 in care homes requires the identification of ideal use cases and a full understanding of contextual and usability factors that affect test results and minimise biosafety risks. This paper presents findings from a scoping-usability and test performance study of a microfluidic immunofluorescence assay for COVID-19 in care homes. Methods A mixed-methods evaluation was conducted in four UK care homes to scope usability and to assess the agreement with qRT-PCR. A dry run with luminescent dye was carried out to explore biosafety issues. Results The agreement analysis was carried out on 227 asymptomatic participants (159 staff and 68 residents) and 14 symptomatic participants (5 staff and 9 residents). Asymptomatic specimens showed 50% (95% CI: 1.3%-98.7%) positive agreement and 96% (95% CI: 92.5%-98.1%) negative agreement with overall prevalence and bias-adjusted Kappa (PABAK) of 0.911 (95% CI: 0.857-0.965). Symptomatic specimens showed 83.3% (95% CI: 35.9%-99.6%) positive agreement and 100% (95% CI: 63.1%-100%) negative agreement with overall prevalence and bias-adjusted Kappa (PABAK) of 0.857 (95% CI: 0.549-1). The dry run showed four main sources of contamination that led to the modification of the standard operating procedures. Simulation after modification showed no further evidence of contamination. Conclusion Careful consideration of biosafety issues and contextual factors associated with care home are mandatory for safe use the POCT. Whilst POCT may have some utility for ruling out COVID-19, further diagnostic accuracy evaluations are needed to promote effective adoption.
Subject(s)
COVID-19ABSTRACT
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 hours, 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.
Subject(s)
COVID-19 , Occupational DiseasesABSTRACT
Background: Point-of-care (POC) tests for COVID-19 could relieve pressure on isolation resource, support infection prevention and control, and help commence more timely and appropriate treatment. We aimed to undertake a systematic review and pooled diagnostic test accuracy study of available individual patient data (IPD) to evaluate the diagnostic accuracy of a commercial POC test (FebriDx) in patients with suspected COVID-19. Methods: A literature search was performed on the 1st of October 2020 to identify studies reporting diagnostic accuracy statistics of the FebriDx POC test versus real time reverse transcriptase polymerase chain reaction (RT-PCR) testing for SARS-CoV-2. Studies were screened for risk of bias. IPD were sought from studies meeting the inclusion and exclusion criteria. Logistic regression was performed to investigate the study effect on the outcome of the RT-PCR test result in order to determine whether it was appropriate to pool results. Diagnostic accuracy statistics were calculated with 95% confidence intervals (CIs). Results: 15 studies were screened, and we included two published studies with 527 hospitalised patients. 523 patients had valid FebriDx results for Myxovirus resistance protein A (MxA), an antiviral host response protein. The FebriDx test produced a pooled sensitivity of 0.920 (95% CI: 0.875-0.950) and specificity of 0.862 (0.819-0.896) compared with RT-PCR, where there was an estimated true COVID-19 prevalence of 0.405 (0.364-0.448) and overall FebriDx test yield was 99.2%. Patients were tested at a median of 4 days [interquartile range: 2:9] after symptom onset. No differences were found in a sub-group analysis of time tested since the onset of symptoms. Conclusions: Based on a large sample of patients from two studies during the first wave of the SARS-CoV-2 pandemic, the FebriDx POC test had reasonable diagnostic accuracy in a hospital setting with high COVID-19 prevalence, out of influenza season. More research is required to determine how FebriDx would perform in other healthcare settings with higher or lower COVID-19 prevalence, different patient populations, or when other respiratory infections are in circulation.