Multicentre diagnostic evaluation of OnSite COVID-19 Rapid Test (CTK Biotech) among symptomatic individuals in Brazil and The United Kingdom

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 clinical sensitivity of the OnSite COVID-19 Rapid test in Brazil was 90.3% [95% Cl 75.1 - 96.7%] and in the United Kingdom was 75.3% [95% Cl 64.6 - 83.6%]. The clinical specificity in Brazil was 99.4% [95% Cl 98.1 - 99.8%] and in the United Kingdom was 95.5% [95% Cl 90.6 - 97.9%]. 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. This study provides comparative performance of an Ag-RDT across two different settings, geographical areas, and population. Overall, the OnSite Ag-RDT demonstrated a lower clinical sensitivity than claimed by the manufacturer... Sensitivity and specificity from the Brazil study fulfilled the performance criteria determined by the World Health Organisation but the performance obtained from the UK study failed to. Further evaluation of the use of Ag-RDTs should include harmonised protocols between laboratories to facilitate comparison between settings.

Head-to head comparison of anterior nares and nasopharyngeal swabs for SARS-CoV-2 antigen detection in a community drive-through test centre in the UK

ObjectiveTo 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). MethodsNP 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. ResultsA 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 ({kappa}) 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. Conclusionsthe 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.

Evaluation of Eight Lateral Flow Tests For The Detection Of Anti-SARS-CoV-2 Antibodies In A Vaccinated Population

With the distribution of COVID-19 vaccinations across the globe and the limited access in many countries, quick determination of an individuals antibody status could be beneficial in allocating limited vaccine doses in low- and middle-income countries (LMIC). Antibody lateral flow tests (LFTs) have potential to address this need as a quick, point of care test, they also have a use case for identifying sero-negative individuals for novel therapeutics, and for epidemiology. Here we present a proof-of-concept evaluation of eight LFT brands using sera from 95 vaccinated individuals to determine sensitivity for detecting vaccination generated antibodies. All 95 (100%) participants tested positive for anti-spike antibodies by the chemiluminescent microparticle immunoassay (CMIA) reference standard post-dose two of their SARS-CoV-2 vaccine: BNT162b2 (Pfizer/BioNTech, n=60), AZD1222 (AstraZeneca, n=31), mRNA-1273 (Moderna, n=2) and Undeclared Vaccine Brand (n=2). Sensitivity increased from dose one to dose two in six out of eight LFTs with three tests achieving 100% sensitivity at dose two in detecting anti-spike antibodies. These tests are quick, low-cost point-of-care tools that can be used without prior training to establish antibody status and may prove valuable for allocating limited vaccine doses in LMICs to ensure those in at risk groups access the protection they need. Further investigation into their performance in vaccinated peoples is required before more widespread utilisation is considered.

Analytical evaluation of thirty-two SARS-CoV-2 lateral flow antigen tests demonstrates sensitivity remains with the SARS-CoV-2 Gamma lineage.

The limit of detection (LOD) of thirty-two antigen lateral flow tests (Ag-RDT) were evaluated with the SARS-CoV-2 Gamma variant. Twenty-eight of thirty-two Ag-RDTs exceeded the World Health Organization criteria of an LOD of 1.0x106 genome copy numbers/ml and performance was equivalent as with the 2020 B.1 lineage and Alpha variant.

A prospective diagnostic evaluation of accuracy of self-taken and healthcare worker-taken swabs for rapid COVID-19 testing

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

Streptococcus pneumoniae colonisation associates with impaired adaptive immune responses against SARS-CoV-2

Although recent epidemiological data suggest that pneumococci may contribute to the risk of SARS-CoV-2 disease, secondary pneumococcal pneumonia has been reported as infrequent. This apparent contradiction may be explained by interactions of SARS-CoV-2 and pneumococcus in the upper airway, resulting in the escape of SARS-CoV-2 from protective host immune responses. Here, we investigated the relationship of these two respiratory pathogens in two distinct cohorts of a) healthcare workers with asymptomatic or mildly symptomatic SARS-CoV-2 infection identified by systematic screening and b) patients with moderate to severe disease who presented to hospital. We assessed the effect of co-infection on host antibody, cellular and inflammatory responses to the virus. In both cohorts, pneumococcal colonisation was associated with diminished anti-viral immune responses, which affected primarily mucosal IgA levels among individuals with mild or asymptomatic infection and cellular memory responses in infected patients. Our findings suggest that S. pneumoniae modulates host immunity to SARS-CoV-2 and raises the question if pneumococcal carriage also enables immune escape of other respiratory viruses through a similar mechanism and facilitates reinfection occurrence.

Detection of SARS-CoV-2 infection by saliva and nasopharyngeal sampling in frontline healthcare workers: an observational cohort study.

BackgroundThe SARS-CoV-2 pandemic has caused an unprecedented strain on healthcare systems worldwide, including the UK National Health Service (NHS). During the first wave of SARS-CoV-2 transmission in UK, SARS-CoV-2 NHS diagnostic test availability was limited to self-isolating symptomatic staff. The burden of symptomatic and asymptomatic infection in healthcare workers (HCW) attending work was unknown. MethodsWe conducted an observational cohort study of SARS-CoV-2 infection in HCW working in an acute NHS Trust during the first wave of the COVID-19 pandemic, using serial self-collected saliva and nasopharyngeal (NP) samples. We also collected self-assessed symptom profiles and isolation behaviours. We retrospectively compared SARS-CoV-2 detection by RT-PCR from saliva (weekly) and NP swabs (twice weekly) from 85 individuals in this cohort and evaluated the association with symptoms. FindingsOver a 12-week period from 30th March 2020, 40% (n=34/85, CI95% 31.3-51.8%) HCWs had evidence of SARS-CoV-2 infection by surveillance NP swab and/or saliva RT-qPCR. Agreement between paired saliva and NP swabs was poor (28.6%, CI95% 13.2-48.7%) with both methods detecting symptomatic and asymptomatic infections. Symptoms were reported by 47.1% (n=40) and self-isolation by 25.9% participants (n=22). Only 41.2% (n=14/34) participants with SARS-CoV-2 infection reported any symptoms within 14 days of the infection. InterpretationHCWs are a potential source of SARS-CoV-2 transmission in hospitals and symptom screening will identify the minority of infections in HCW. Saliva is an easily accessible fluid sample for screening for SARS-CoV-2 infection and in addition to NP swab, facilitated ascertainment of symptomatic and asymptomatic cases in this setting. Combined saliva and NP testing would improve detection of SARS-CoV-2 for surveillance. Better understanding of transmissibility from asymptomatic staff using transmission-based infection precautions, is required to inform policy.

Limit of detection in different matrices of nineteen commercially available rapid antigen tests for the detection of SARS-CoV-2

In the context of the coronavirus disease 2019 (COVID-19) pandemic there has been an increase of the use of antigen-detection rapid diagnostic tests (Ag-RDT). The performance of Ag-RDT vary greatly between manufacturers and evaluating their analytical limit of detection (LOD) has become high priority. Here we describe a manufacturer-independent evaluation of the LOD of 19 marketed Ag-RDT using live SARS-CoV-2 spiked in different matrices: direct culture supernatant, a dry swab, and a swab in Amies. Additionally, the LOD using dry swab was investigated after 7 days storage at -80{degrees}C of the SARS-CoV-2 serial dilutions. An LOD of {approx} 5.0 x 102 pfu/ml (1.0 x 106 genome copies/ml) in culture media is defined as acceptable by the World Health Organization. Fourteen of nineteen Ag-RDTs (ActiveXpress, Espline, Excalibur, Innova, Joysbio, Mologic, NowCheck, Orient, PanBio, RespiStrip, Roche, Standard-F, Standard-Q and Sure-Status) exceeded this performance criteria using direct culture supernatant applied to the Ag-RDT. Six Ag-RDT were not compatible with Amies media and a decreased sensitivity of 2 to 20-fold was observed for eleven tests on the stored dilutions at -80{degrees}C for 7 days. Here, we provide analytical sensitivity data to guide appropriate test and sample type selection for use and for future Ag-RDT evaluations.

Self-sampling of capillary blood for serological testing of SARS-CoV-2 by COVID-19 IgG ELISA

Serological testing is emerging as a powerful tool to progress our understanding of COVID-19 exposure, transmission and immune response. Large-scale testing is limited by the need for in-person blood collection by staff trained in venepuncture. Capillary blood self-sampling and postage to laboratories for analysis could provide a reliable alternative. Two-hundred and nine matched venous and capillary blood samples were obtained from thirty nine participants and analysed using a COVID-19 IgG ELISA to detect antibodies against SARS-CoV-2. Thirty seven out of thirty eight participants were able to self-collect an adequate sample of capillary blood ([≥]50 l). Using plasma from venous blood collected in lithium heparin as the reference standard, matched capillary blood samples, collected in lithium heparin-treated tubes and on filter paper as dried blood spots, achieved a Cohen's kappa coefficient of >0.88 (near-perfect agreement). Storage of capillary blood at room temperature for up to 7 days post sampling did not affect concordance. Our results indicate that capillary blood self-sampling is a reliable and feasible alternative to venepuncture for serological assessment in COVID-19.

Variation of SARS-CoV-2 viral loads by sample type, disease severity and time: a systematic review

BackgroundTo describe whether SARS-CoV-2 viral loads (VLs) and cycle thresholds (CTs) vary by sample type, disease severity and symptoms duration. MethodsSystematic searches were conducted in MEDLINE, EMBASE, BioRxiv and MedRxiv. Studies reporting individual SARS-CoV-2 VLs and/or CT values from biological samples. Paired reviewers independently screened potentially eligible articles. CT values and VLs distributions were described by sample type, disease severity and time from symptom onset. Differences between groups were examined using Kruskal-Wallis and Dunn s tests (post-hoc test). The risk of bias was assessed using the Joanna Briggs Critical Appraisal Tools. Results14 studies reported CT values, 8 VLs and 2 CTs and VLs, resulting in 432 VL and 873 CT data points. VLs were higher in saliva and sputum (medians 4.7x108 and 6.5x104 genomes per ml, respectively) than in nasopharyngeal and oropharyngeal swabs (medians 1.7x102 and 4.8x103). Combined naso/oropharyngeal swabs had lower CT values (i.e. higher VLs) than single site samples (p=<0.0001). CT values were also lower in asymptomatic individuals and patients with severe COVID-19 (median CT 30 for both) than among patients with moderate and mild symptoms (31.4 and 31.3, respectively). Stool samples were reported positive for a longer period than other specimens. ConclusionVLs are higher in saliva and sputum and in individuals who are asymptomatic of with severe COVID-19. Diagnostic testing strategies should consider that VLs vary by sample type, disease severity and time since symptoms onset. SummaryThis systematic review found a higher viral load in saliva and sputum than in nasopharyngeal swabs, in asymptomatic individuals and patients with severe COVID-19. Diagnostic testing strategies should consider the type of sample, disease severity and the time since symptoms onset.

Saliva offers a sensitive, specific and non-invasive alternative to upper respiratory swabs for SARS-CoV-2 diagnosis.

RT-qPCR utilising upper respiratory swabs are the diagnostic gold standard for SARS-CoV-2 despite reported low sensitivity and limited scale up due to global shortages. Saliva is a non-invasive, equipment independent alternative to swabs. We collected 145 paired saliva and nasal/throat (NT) swabs at diagnosis (day 0) and repeated on day 2 and day 7 dependent on inpatient care and day 28 for study follow up. Laboratory cultured virus was used to determine the analytical sensitivity of spiked saliva and swabs containing amies preservation media. Self-collected saliva samples were found to be consistent, and in some cases superior when compared to healthcare worker collected NT swabs from COVID-19 suspected participants. We report for the first time the analytical limit of detection of 10-2and 100 pfu/ml for saliva and swabs respectively. Saliva is a easily self-collected, highly sensitive specimen for the detection of SARS-CoV-2.

Rapid development of COVID-19 rapid diagnostics for low resource settings: accelerating delivery through transparency, responsiveness, and open collaboration

Here we describe an open and transparent consortium for the rapid development of COVID-19 rapid diagnostics tests. We report diagnostic accuracy data on the Mologic manufactured IgG COVID-19 ELISA on known positive serum samples and on a panel of known negative respiratory and viral serum samples pre-December 2019. In January, Mologic, embarked on a product development pathway for COVID-19 diagnostics focusing on ELISA and rapid diagnostic tests (RDTs), with anticipated funding from Wellcome Trust and DFID. 834 clinical samples from known COVID-19 patients and hospital negative controls were tested on Mologics IgG ELISA. The reported sensitivity on 270 clinical samples from 124 prospectively enrolled patients was 94% (95% CI: 89.60% - 96.81%) on day 10 or more post laboratory diagnosis, and 96% (95% CI: 84.85% - 99.46%) between 14-21 days post symptom onset. A specificity panel comprising 564 samples collected pre-December 2019 were tested to include most common respiratory pathogens, other types of coronavirus, and flaviviruses. Specificity in this panel was 97% (95% CI: 95.65% - 98.50%). This is the first in a series of Mologic products for COVID-19, which will be deployed for COVID-19 diagnosis, contact tracing and sero-epidemiological studies to estimate disease burden and transmission with a focus on ensuring access, affordability, and availability to low-resource settings.