The potential for rapid antigen testing for mucormycosis in the context of COVID-19

INTRODUCTION

Mucormycosis is a highly aggressive angio-invasive disease of humans caused by Mucorales fungi. Prior to the COVID-19 pandemic, mucormycosis was a rare mycosis typically seen in immunocompromised patients with hematological malignancies or in transplant recipients. During the second wave of the pandemic, there was a dramatic increase in the disease, especially in India where a unique set of circumstances led to large numbers of life-threatening and disfiguring rhino-orbital-cerebral mucormycosis (ROCM) infections.

AREAS COVERED

The review examines mucormycosis as a super-infection of COVID-19 patients, and the risk factors for COVID-19-associated mucormycosis (CAM) that drove the ROCM epidemic in India. The limitations of current diagnostic procedures are identified, and the measures needed to improve the speed and accuracy of detection discussed.

EXPERT OPINION

Despite increased awareness, global healthcare systems remain unprepared for further outbreaks of ROCM. Current diagnosis of the disease is slow and inaccurate, negatively impacting on patient survival. This is most evident in low- to middle-income countries which lack suitably equipped diagnostic facilities for rapid identification of the infecting pathogens. Rapid antigen testing using point-of-care lateral-flow assays could potentially have aided in the quick and accurate diagnosis of the disease, allowing earlier intervention with surgery and Mucorales-active antifungal drugs.

SARS-CoV-2 viral dynamics in a placebo-controlled phase 2 study of patients infected with the SARS-CoV-2 Omicron variant and treated with pomotrelvir

Current guidelines recommend that individuals with moderate COVID-19 disease isolate for 5 days after the first appearance of symptoms or a positive SARS-CoV-2 test. It would be useful to understand the time course of infectious virus production and its correlation with virus detection using a rapid antigen test (RAT) or quantitative reverse transcriptase (qRT)-PCR. In a phase 2 study, 242 vaccinated patients with COVID-19 and at low risk for progression to severe disease initiated 5 days of treatment with pomotrelvir (PBI-0451, a SARS-CoV-2 main protease inhibitor) or placebo within 5 days after symptom onset. The primary endpoint, the proportion of subjects with SARS-CoV-2 viral titers below the limit of detection on Day 3 of treatment in the pomotrelvir versus placebo groups, was not met. No between-group differences in SARS-CoV-2 clearance or symptom resolution or alleviation were observed. Additional analyses evaluated the dynamics of SARS-CoV-2 replication in mid-turbinate nasal swabs and saliva samples using infectious virus assay (IVA), RAT, and qRT-PCR. SARS-CoV-2 cleared rapidly, with negative results first determined by IVA (TCID50 below the limit of detection), followed by the RAT (negative for SARS-CoV-2 N antigen), and qRT-PCR (RNA below the limit of detection), which suggests that delayed initiation of treatment (up to 5 days after symptom onset) may have contributed to the lack of treatment response. Symptom resolution lagged behind viral clearance assessed by IVA and RAT. These data support reliance on a negative RAT to determine when an individual is no longer producing infectious virus and may end isolation.IMPORTANCEA phase 2 double-blind, placebo-controlled study was performed evaluating pomotrelvir, a SARS-CoV-2 Mpro inhibitor, compared with placebo in 242 non-hospitalized, vaccinated, symptomatic adults with COVID-19 (Omicron). No improvement in the decrease of viral replication or relief of symptoms was observed between the two groups when treatment was initiated ≥3 days after symptom onset. These results suggest that future COVID-19 antiviral studies using a similar patient population may need to initiate treatment earlier, like influenza studies. This is the first study to prospectively evaluate SARS-CoV-2 viral dynamics and the time to viral clearance in a significant number of patients using concurrently obtained results from an infectious virus assay, a rapid antigen test (RAT), and a qRT-PCR assay over a 15-day time course. These results suggest that a negative RAT assay is a good indicator of loss of infectious virus and the ability to return to normal activities.

Impact of Omicron variant sublineage BA.2.75 on the OnSite COVID-19 Ag Rapid Test: the applicability of rapid antigen test with universal transport media

BACKGROUND

Rapid antigen testing (RAT) is one of the most powerful tools for SARS-CoV-2 detection. The OnSite COVID-19 Ag Rapid Test is an antigen-based, point-of-care test approved by the WHO for Emergency Use Listing. The Nucleocapsid (N) gene mutations found in the emerging Omicron sublineages lead to the question of RAT performance.

OBJECTIVE

To ensure the diagnostic performance of the study RAT during rapidly mutated Omicron variants.

RESULTS

We independently evaluated the performance of this assay in 1098 archived samples collected in Thailand during October 2022-February 2023, which were 798 and 300 COVID-19 real-time RT-PCR positive and negative, respectively. The assay performed with 100% sensitivity and 100% specificity using a cycle threshold (Ct) of <20 for the RT-PCR. The sensitivity decreased to 88% when using Ct <30. Most of the SARS-CoV-2 found were Omicron BA.2 (99%), harboring six known N mutations (P13L, E31del, S33del, R203K, G204R and S413R). Eight samples containing hybrid variants (XBB.1*, XBB.2 and XBJ) were detected by the study RAT. This RAT detects all Omicron sublineages known to be circulating in Thailand.

CONCLUSIONS

These results confirmed the good performance of the study RAT for detecting Omicron variants and its appropriateness for individual diagnosis and for genomic surveillance.

Model for Interpreting Discordant SARS-CoV-2 Diagnostic Test Results

We devised a model to interpret discordant SARS-CoV-2 test results. We estimate that, during March 2020-May 2022, a patient in the United States who received a positive rapid antigen test result followed by a negative nucleic acid test result had only a 15.4% (95% CI 0.6%-56.7%) chance of being infected.

A high throughput immuno-affinity mass spectrometry method for detection and quantitation of SARS-CoV-2 nucleoprotein in human saliva and its comparison with RT-PCR, RT-LAMP, and lateral flow rapid antigen test

OBJECTIVES

Many reverse transcription polymerase chain reaction (RT-PCR) methods exist that can detect SARS-CoV-2 RNA in different matrices. RT-PCR is highly sensitive, although viral RNA may be detected long after active infection has taken place. SARS-CoV-2 proteins have shorter detection windows hence their detection might be more meaningful. Given salivary droplets represent a main source of transmission, we explored the detection of viral RNA and protein using four different detection platforms including SISCAPA peptide immunoaffinity liquid chromatography-mass spectrometry (SISCAPA-LC-MS) using polyclonal capture antibodies.

METHODS

The SISCAPA-LC MS method was compared to RT-PCR, RT-loop-mediated isothermal amplification (RT-LAMP), and a lateral flow rapid antigen test (RAT) for the detection of virus material in the drool saliva of 102 patients hospitalised after infection with SARS-CoV-2. Cycle thresholds (Ct) of RT-PCR (E gene) were compared to RT-LAMP time-to-positive (TTP) (NE and Orf1a genes), RAT optical densitometry measurements (test line/control line ratio) and to SISCAPA-LC-MS for measurements of viral protein.

RESULTS

SISCAPA-LC-MS showed low sensitivity (37.7 %) but high specificity (89.8 %). RAT showed lower sensitivity (24.5 %) and high specificity (100 %). RT-LAMP had high sensitivity (83.0 %) and specificity (100.0 %). At high initial viral RNA loads (<20 Ct), results obtained using SISCAPA-LC-MS correlated with RT-PCR (R2 0.57, p-value 0.002).

CONCLUSIONS

Detection of SARS-CoV-2 nucleoprotein in saliva was less frequent than the detection of viral RNA. The SISCAPA-LC-MS method allowed processing of multiple samples in <150 min and was scalable, enabling high throughput.

Use of Rapid Antigen Triple Test Nasal Swabs (COVID-VIRO ALL-IN TRIPLEX: Severe Acute Respiratory Syndrome Coronavirus 2, Respiratory Syncytial Virus, and Influenza) in Children With Respiratory Symptoms: A Real-life Prospective Study

Background

In autumn 2022, the epidemics due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respiratory syncytial virus (RSV), and influenza overlapped, and these diseases can present with the same symptomatology. The use of a triple antigen test (SARS-CoV-2 + influenza A/B + RSV) seems crucial for accurate viral diagnosis in the context of implementing long-acting monoclonal antibody vaccination against RSV in the upcoming RSV season.

Methods

We assessed the usefulness of the triple test in real life in this prospective study performed from October 2022 to May 2023 and involving 116 pediatricians (2 emergency department pediatricians and 114 ambulatory pediatricians). Children <15 years old with flu-like illness (with fever), bronchiolitis (dyspnea ± wheezing), otitis, and croup were enrolled and sampled with a nasal triple test.

Results

For 8329 children with flu-like illness (65.3%), bronchiolitis (17.9%), otitis (8.8%), and croup (6.3%), the use of the triple test led to a viral diagnosis in 47.9% of cases. The highest RSV positivity occurred in children with bronchiolitis (32.9%). The highest influenza A and B positivity (24.6% and 19.6%) occurred in children with flu-like illness. A succession of 3 epidemics (RSV and influenza A and B) occurred over time with several overlap periods.

Conclusions

The triple test allowed for a viral diagnosis in half of our cases. The upcoming introduction of RSV prevention will emphasize the need for active surveillance with viral results both in ambulatory settings and hospitals. Clinical Trials Registration. NCT0441231.

Development and Clinical Performance of InteliSwab® COVID-19 Rapid Test: Evaluation of Antigen Test for the Diagnosis of SARS-CoV-2 and Analytical Sensitivity to Detect Variants of Concern Including Omicron and Subvariants

BACKGROUND AND OBJECTIVES

Timely detection of SARS-CoV-2 infection with subsequent contact tracing and rapid isolation are considered critical to containing the pandemic, which continues with the emergence of new variants. Hence, there is an ongoing need for reliable point-of-care antigen rapid diagnostic tests (Ag-RDT). This report describes the development, evaluation, and analytical sensitivity of the diagnostic performance of the InteliSwab® COVID-19 Rapid Test. Methods: Samples from 165 symptomatic subjects were tested with InteliSwab® and the results were compared to RT-PCR to determine the antigen test performance. The analytical sensitivity of InteliSwab® for the detection of different variants was assessed by limit of detection (LOD) determination using recombinant nucleocapsid proteins (NPs) and testing with virus isolates. Western immunoblot independently confirmed that each monoclonal Ab is capable of binding to all variants tested thus far.

RESULTS

The overall positivity rate by RT-PCR was 37% for the 165 symptomatic subjects. Based on RT-PCR results as the reference standard, InteliSwab® showed clinical sensitivity and specificity of 85.2% (95% CI, 74.3-92.0%) and 98.1% (95% CI, 93.3-99.7%), respectively. The overall agreement was 93.3% (Kappa index value 0.85; 95% CI, 0.77-0.74) between RT-PCR and InteliSwab® test results. Furthermore, the evaluation of analytical sensitivity for different SARS-CoV-2 variants by InteliSwab® was comparable in the detection of all the variants tested, including Omicron subvariants, BA.4, BA.5, and BQ.1.

CONCLUSIONS

Due to the surge of infections caused by different variants from time to time, there is a critical need to evaluate the sensitivity of rapid antigen-detecting tests for new variants. The study findings showed the robust diagnostic performance of InteliSwab® and analytical sensitivity in detecting different SARS-CoV-2 variants, including the Omicron subvariants. With the integrated swab and excellent sensitivity and variant detection, this test has high potential as a point-of-care Ag-RDT in various settings when molecular assays are in limited supply and rapid diagnosis of SARS-CoV-2 is necessary.

Evaluation of Multiplex Rapid Antigen Tests for the Simultaneous Detection of SARS-CoV-2 and Influenza A/B Viruses

Single-target rapid antigen tests (RATs) are commonly used to detect highly transmissible respiratory viruses (RVs), such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza viruses. The simultaneous detection of RVs presenting overlapping symptoms is vital in making appropriate decisions about treatment, isolation, and resource utilization; however, few studies have evaluated multiplex RATs for SARS-CoV-2 and other RVs. We assessed the diagnostic performance of multiplex RATs targeting both the SARS-CoV-2 and influenza A/B viruses with the GenBody Influenza/COVID-19 Ag Triple, InstaView COVID-19/Flu Ag Combo (InstaView), STANDARDTM Q COVID-19 Ag Test, and STANDARDTM Q Influenza A/B Test kits using 974 nasopharyngeal swab samples. The cycle threshold values obtained from the real-time reverse transcription polymerase chain reaction results showed higher sensitivity (72.7-100%) when the values were below, rather than above, the cut-off values. The InstaView kit exhibited significantly higher positivity rates (80.21% for SARS-CoV-2, 61.75% for influenza A, and 46.15% for influenza B) and cut-off values (25.57 for SARS-CoV-2, 21.19 for influenza A, and 22.35 for influenza B) than the other two kits, and was able to detect SARS-CoV-2 Omicron subvariants. Therefore, the InstaView kit is the best choice for routine screening for both SARS-CoV-2 and influenza A/B in local communities.

Sensitivity of rapid antigen tests against SARS-CoV-2 Omicron and Delta variants

Rapid antigen tests (RATs) have become an invaluable tool for combating the COVID-19 pandemic. However, concerns have been raised regarding the ability of existing RATs to effectively detect emerging SARS-CoV-2 variants. We compared the performance of 10 commercially available, emergency use authorized RATs against the Delta and Omicron SARS-CoV-2 variants using both individual patient and serially diluted pooled clinical samples. The RATs exhibited lower sensitivity for Omicron samples when using PCR cycle threshold (CT) value (a rough proxy for RNA concentration) as the comparator. Interestingly, however, they exhibited similar sensitivity for Omicron and Delta samples when using quantitative antigen concentration as the comparator. We further found that the Omicron samples had lower ratios of antigen to RNA, which offers a potential explanation for the apparent lower sensitivity of RATs for that variant when using C T value as a reference. Our findings underscore the complexity in assessing RAT performance against emerging variants and highlight the need for ongoing evaluation in the face of changing population immunity and virus evolution.

Evaluation of "Test to Return" after COVID-19 Diagnosis in a Massachusetts Public School District

BACKGROUND

Per Centers for Disease Control and Prevention guidance, students with COVID-19 may end isolation after 5 days if symptoms are improving; some individuals may still be contagious. Rapid antigen testing identifies possibly infectious virus. We report on a test-to-return (TTR) program in a Massachusetts school district to inform policy decisions about return to school after COVID-19.

METHODS

During the 2021-2022 Omicron BA.1 surge, students with COVID-19 could return on day 6-10 if they met symptom criteria and had a negative rapid test; students with positive rapid tests and those who declined TTR remained isolated until day 11. TTR positivity rates were compared by grade level, vaccination status, symptom status, and day of infection.

RESULTS

31.4% of students had a positive TTR rapid test; there were no differences by grade or vaccination status. Ever-symptomatic students were more likely to have a positive rapid test (75/174 [43.1%] vs 18/104 [17.3%]). For ever-symptomatic students, TTR positivity decreased by day of infection.

CONCLUSIONS

A substantial proportion of students may still be contagious 6 days after onset of COVID-19 infection. TTR programs may increase or reduce missed school days, depending on when return is otherwise allowed (day 6 or 11). The impact of TTR programs on school-associated transmission remains unknown.

Can variants, reinfection, symptoms and test types affect COVID-19 diagnostic performance? A large-scale retrospective study of AG-RDTs during circulation of Delta and Omicron variants, Czechia, December 2021 to February 2022

BackgroundThe sensitivity and specificity of selected antigen detection rapid diagnostic tests (AG-RDTs) for SARS-CoV-2 were determined in the unvaccinated population when the Delta variant was circulating. Viral loads, dynamics, symptoms and tissue tropism differ between Omicron and Delta.AimWe aimed to compare AG-RDT sensitivity and specificity in selected subgroups during Omicron vs Delta circulation.MethodsWe retrospectively paired AG-RDT results with PCRs registered in Czechia's Information System for Infectious Diseases from 1 to 25 December 2021 (Delta, n = 20,121) and 20 January to 24 February 2022 (Omicron, n = 47,104).ResultsWhen confirmatory PCR was conducted on the same day as AG-RDT as a proxy for antigen testing close to peak viral load, the average sensitivity for Delta was 80.4% and for Omicron 81.4% (p < 0.05). Sensitivity in vaccinated individuals was lower for Omicron (OR = 0.94; 95% confidence interval (CI): 0.87-1.03), particularly in reinfections (OR = 0.83; 95% CI: 0.75-0.92). Saliva AG-RDT sensitivity was below average for both Delta (74.4%) and Omicron (78.4%). Tests on the European Union Category A list had higher sensitivity than tests in Category B. The highest sensitivity for Omicron (88.5%) was recorded for patients with loss of smell or taste, however, these symptoms were almost 10-fold less common than for Delta. The sensitivity of AG-RDTs performed on initially asymptomatic individuals done 1, 2 or 3 days before a positive PCR test was consistently lower for Omicron compared with Delta.ConclusionSensitivity for Omicron was lower in subgroups that may become more common if SARS-CoV-2 becomes an endemic virus.

Evaluation of a Rapid Urine Antigen Detection Assay as a Point-of-Care Test in the Diagnosis of Community-Acquired Pneumonia

Introduction Community-acquired pneumonia (CAP) is among the most common public health problems encountered throughout the world. CAP is a frequent cause of lower respiratory tract infections among children and geriatric-age persons. The etiology of CAP is complex but generally involves infection with bacteria like Streptococcus pneumoniae (S. pneumoniae), which is the most common cause of CAP. The underdiagnosis of CAP due to the limitations of conventional culture methods could be responsible for severe morbidity and mortality, especially among susceptible populations. We evaluated the usefulness of a rapid immunochromatographic test (BinaxNOW™, Abbott, Chicago, IL) that detects S. pneumoniae through a rapid urine antigen test (RUAT) as a point-of-care (POC) diagnostic method in the early detection of CAP. Methods A prospective study was conducted in a university-affiliated teaching hospital between January 2019 and September 2019 (nine months). The study recruited 300 inpatients who revealed signs and symptoms associated with pneumonia. The study was approved by the institutional ethics committee, and all participants provided their voluntary informed consent. Laboratory evaluation included the collection of sputum samples, which were processed for Gram stain and routine culture. Five milliliters of blood were collected from all the subjects for carrying out a blood culture. A urine sample was collected from each participant for the detection of S. pneumoniae through the point-of-care urinary antigen test. Results Of the 300 patients diagnosed with CAP, the S. pneumoniae RUAT was positive in 110 out of 140 cases of pneumococcal pneumoniae (78.57%). The RUAT results were positive for 20 (66.6%) out of 30 bacteremic patients and for 90 (81.8%) out of 110 patients positive for sputum culture. The RUAT was positive in 10 out of 20 cases of pneumonia with an unknown microbial etiology. The overall sensitivity (78.57%), specificity (100%), positive predictive value (100%), negative predictive value (98.88%), and accuracy (90%) of the RUAT were similar to sputum culture results.  Conclusion The RUAT has shown comparable efficacy with sputum culture and therefore can be used as a complementary approach to conventional methods in the early diagnosis of CAP caused by S. pneumoniae. Due to its ease of use and rapid results, it could be incorporated as a POC diagnostic test.

Association Between Rapid Antigen Detection Tests and Real-Time Reverse Transcription-Polymerase Chain Reaction Assay for SARS-CoV-2: A Systematic Review and Meta-Analyses

Objectives: We aimed to assess the association between rapid antigen detection tests and real-time reverse transcription-polymerase chain reaction assay for severe acute respiratory syndrome coronavirus 2. Methods: We searched PubMed, Cochrane Library, EMBASE, and the Web of Science from their inception to 31 May 2023. A random-effects meta-analysis was used to estimate false positives in the RADTs group, relative to those in the RT-PCR group, and subgroup analyses were conducted based on the different Ct value cut-offs (<40 or ≥40). We performed this study in accordance with the guidelines outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Results: Fifty-one studies were included and considered to be of moderate quality. We found a satisfactory overall false positive rate (0.01, 95% CI: 0.00-0.01) for the RADTs compared to RT-PCR. In the stratified analysis, we also found that the false positive rates of the RADTs did not increase when Ct values of RT-PCR (Ct < 40, 0.01, 95% CI: 0.00-0.01; Ct ≥ 40, 0.01, 95% CI: 0.00-0.01). Conclusion: In conclusion, the best available evidence supports an association between RADTs and RT-PCR. When Ct-values were analyzed using cut-off <40 or ≥40, this resulted in an estimated false positive rate of only 1%.

To PCR or not? The impact of shifting policy from PCR to rapid antigen tests to diagnose COVID-19 during the omicron epidemic: a nationwide surveillance study

Background

Coronavirus disease 2019 (COVID-19) had caused huge impacts worldwide. Polymerase chain reaction (PCR) is the mainstay diagnostic modality. In most hospitals in Taiwan, samples for PCR are collected at emergency department (ER) or outdoor clinics to avoid virus spread inside hospitals. Home rapid antigen test (RAT) is a feasible, low-cost, and convenient tool with moderate sensitivity and high specificity, which can be performed at home to reduce hospital visits. Due to comparably low severity of omicron variant and high vaccine coverage (~80% residents fully vaccinated with AstraZeneca, Moderna, or Pfizer BioNTech COVID-19 vaccines as of March 2022), the policy was shifted from containment to co-existing with COVID-19 in Taiwan. Virus spread rapidly in the community after the ease of social restrictive measurements. To acquire a confirmed diagnosis, PCR testing was requested for people with suspected COVID-19 infection. As a consequence, people with respiratory symptoms or contact history surged into hospitals for PCR testing, thus, the medical capacity was challenged. The diagnostic policy was altered from PCR to RAT, but the impact of diagnostic policy change remains unclear.

Objectives

We conducted this study to investigate the number of COVID-19 cases, PCR testing, hospitalizations, mortalities, and hospital visits during the epidemic and evaluate the impact of diagnostic policy change on hospital visits.

Methods

The diagnostic policy change was implemented in late May 2022. We used nationwide and hospital-based data of COVID-19 cases, PCR testing, hospitalizations, mortalities, and hospital visits before and after policy change as of 31 Jul 2022.

Results

During the omicron epidemic, significant and synchronous increase of COVID-19 patients, PCR testing, hospital visits were observed. COVID-19 cases increased exponentially since April 2022 and the COVID-19 patients peaked in June (1,943, 55,571, and 61,511 average daily new cases in April, May, and June, respectively). The PCR testing peaked in May (85,788 daily tests) with high positive rate (81%). The policy of RAT as confirmatory diagnosis was implemented on 26 May 2022 and a substantial decline of PCR testing numbers occurred (85,788 and 83,113 daily tests in May and June). People hospitalized for COVID-19 peaked in June (821.8 patients per day) and decreased in July (549.5 patients). The mortality cases also peaked in June (147 cases/day). This trend was also validated by the hospital-based data with a significant decrease of emergency department visits (11,397 visits in May while 8,126 visits in June) and PCR testing (21,314 in May and 6,158 in June). The proportion of people purely for PCR testing also decreased (10-26 vs. 5-14%, before and after policy change, respectively).

Conclusions

The impact of diagnostic policy change was a complicated issue and our study demonstrated the huge impact of diagnostic policy on health seeking behavior. The PCR testing numbers and emergency department visits had substantial decrease after diagnostic policy change, and the plateau of epidemic peak eased gradually in ~1 month later. Widespread RAT application may contribute to the decreased hospital visits and preserve medical capacity. Our study provides some evidences for policy maker's reference.

A Reagent and Virus Benchmarking Panel for a Uniform Analytical Performance Assessment of N Antigen-Based Diagnostic Tests for COVID-19

Rapid diagnostic tests (RDTs) that detect antigen indicative of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection can help in making quick health care decisions and regularly monitoring groups at risk of infection. With many RDT products entering the market, it is important to rapidly evaluate their relative performance. Comparison of clinical evaluation study results is challenged by protocol design variations and study populations. Laboratory assays were developed to quantify nucleocapsid (N) and spike (S) SARS-CoV-2 antigens. Quantification of the two antigens in nasal eluates confirmed higher abundance of N than S antigen. The median concentration of N antigen was 10 times greater than S per genome equivalent. The N antigen assay was used in combination with quantitative reverse transcription (RT)-PCR to qualify a panel composed of recombinant antigens, inactivated virus, and clinical specimen pools. This benchmarking panel was applied to evaluate the analytical performance of the SD Biosensor Standard Q COVID-19 antigen (Ag) test, Abbott Panbio COVID-19 Ag rapid test, Abbott BinaxNOW COVID-19 Ag test, and the LumiraDx SARS-CoV-2 Ag test. The four tests displayed different sensitivities toward the different panel members, but all performed best with the clinical specimen pool. The concentration for a 90% probability of detection across the four tests ranged from 21 to 102 pg/mL of N antigen in the extracted sample. Benchmarking panels provide a quick way to verify the baseline performance of a diagnostic and enable direct comparisons between diagnostic tests. IMPORTANCE This study reports the results for severe acute respiratory syndrome coronavirus-2 (SARS-COV-2) nucleocapsid (N) and spike (S) antigen quantification assays and their performance against clinical reverse transcription (RT)-PCR results, thus describing an open-access quantification method for two important SARS-CoV-2 protein analytes. Characterized N antigen panels were used to evaluate the limits of detection of four different rapid tests for SARS-CoV-2 against multiple sources of nucleocapsid antigen, demonstrating proof-of-concept materials and methodology to evaluate SARS-CoV-2 rapid antigen detection tests. Quantification of N antigen was used to characterize the relationship between viral count and antigen concentration among clinical samples and panel members of both clinical sample and viral culture origin. This contributes to a deeper understanding of protein antigen and molecular analytes and presents analytical methods complementary to clinical evaluation for characterizing the performance of both laboratory-based and point-of-care rapid diagnostics for SARS-CoV-2.

Clinical features of COVID-19 rapid antigen test exposures reported by an Australian poisons information centre: a prospective study

INTRODUCTION

Coronavirus disease COVID-19 rapid antigen tests are a useful tool in detecting infection, and their use has increased in many countries since they became commercially available in late 2021. Some rapid antigen tests contain sodium azide, which can be toxic in small doses. This study aimed to describe the clinical characteristics of exposures to COVID-19 rapid antigen tests.

METHODS

This is a prospective study conducted by the New South Wales Poisons Information Centre. From 22 January 2022 to 31 August 2022, rapid antigen test exposures were followed up to obtain outcome information. Data collected included: brand/ingredients, exposure route, demographics, symptoms, and disposition.

RESULTS

We recorded 218 exposures in the seven-month study period. Complete follow-up information was available in 75% (n = 164). There were 53 exposures to sodium azide-containing products (35 with follow-up data) and 165 to non-sodium azide-containing products and unknown ingredient exposures (129 with follow-up data). Overall, unintentional exposures predominated (n = 182), and 151 were ingestions. The vast majority (>90%) did not develop symptoms, and all symptoms that developed were mild. Most cases (95%, n = 208) did not require referral to a healthcare facility.

CONCLUSIONS

In this prospective series, few patients developed symptoms, regardless of the sodium azide content, likely due to low concentration and low volume within the test kits. However, ongoing toxicovigilance is warranted.

Keeping kids in school: modelling school-based testing and quarantine strategies during the COVID-19 pandemic in Australia

Background

In 2021, the Australian Government Department of Health commissioned a consortium of modelling groups to generate evidence assisting the transition from a goal of no community COVID-19 transmission to 'living with COVID-19', with adverse health and social consequences limited by vaccination and other measures. Due to the extended school closures over 2020-21, maximizing face-to-face teaching was a major objective during this transition. The consortium was tasked with informing school surveillance and contact management strategies to minimize infections and support this goal.

Methods

Outcomes considered were infections and days of face-to-face teaching lost in the 45 days following an outbreak within an otherwise COVID-naïve school setting. A stochastic agent-based model of COVID-19 transmission was used to evaluate a 'test-to-stay' strategy using daily rapid antigen tests (RATs) for close contacts of a case for 7 days compared with home quarantine; and an asymptomatic surveillance strategy involving twice-weekly screening of all students and/or teachers using RATs.

Findings

Test-to-stay had similar effectiveness for reducing school infections as extended home quarantine, without the associated days of face-to-face teaching lost. Asymptomatic screening was beneficial in reducing both infections and days of face-to-face teaching lost and was most beneficial when community prevalence was high.

Interpretation

Use of RATs in school settings for surveillance and contact management can help to maximize face-to-face teaching and minimize outbreaks. This evidence supported the implementation of surveillance testing in schools in several Australian jurisdictions from January 2022.

Testing for COVID-19: a 2023 update

Nucleic acid amplification tests (NAATs), including polymerase chain reaction (PCR) assays, are more sensitive for the detection of SARS-CoV-2 than rapid antigen tests (RATS), and are the gold standard for diagnosis of acute COVID-19. However NAATs can remain positive for weeks following infection due to low-level shedding of non-viable viral fragments. RATs (in particular self-testing) are the mainstay of COVID-19 diagnosis due to their convenience, speed and high specificity. The sensitivity of RATs is highest within seven days of symptom onset. A negative RAT result may warrant a NAAT or repeat RAT for confirmation. The presence of spike antibodies is consistent with either vaccination or infection. Nucleocapsid antibodies suggest a previous infection. Serological tests measuring neutralising antibodies that infer immunity are not readily available.

Evaluation of the new 2.0 version of the Roche SARS-CoV-2 Rapid Antigen Test

We evaluated the new 2.0 version of the Roche Diagnostics SARS-CoV-2 Rapid Antigen Test (RAT 2.0) for the detection of SARS-CoV-2. Our evaluation material comprised of nasopharyngeal samples of 140 persons positive for SARS-CoV-2 nucleic acid amplification test (NAAT) and of 100 persons negative for SARS-CoV-2 NAAT. The sensitivity limit of the RAT 2.0 was further estimated with the additional selected samples of 27 persons with high NAAT cycle threshold (Ct) value representing low viral load. For the detection of possible cross-reactions in the RAT 2.0, routine respiratory samples positive for influenza A (N=5), respiratory syncytial virus (RSV) (N=4), or combined RSV and human coronavirus OC43 (N=1) were included in the study material. The overall sensitivity of the RAT 2.0 was 92.1% and specificity 100%. When evaluating the samples with NAAT Ct value ≤30, the sensitivity was 97.0%. All samples for cross-reactivity testing containing other viruses instead of SARS-CoV-2 remained negative in RAT 2.0. According to our findings, this RAT 2.0 offers a reliable tool for the diagnostics of acute COVID-19 in this pandemic environment.

SARS-CoV-2 antigen detection by saliva; an alternative to nasopharyngeal specimen: A cross-sectional study

Background and Aims

Saliva samples are less invasive and more convenient for patients than naso- and/or oropharynx swabs (NOS). However, there is no US Food and Drug Administration-approved severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapid antigen test kit, which can be useful in a prolonged pandemic to reduce transmission by allowing suspected individuals to self-sampling. We evaluated the performances of High sensitive AQ⁺ Rapid SARS-CoV-2 Antigen Test (AQ⁺ kit) using nasopharyngeal swabs (NPs) and saliva specimens from the same patients in laboratory conditions.

Methods

The real-time reverse transcription-polymerase chain reaction (rRT-PCR) test result was used for screening the inrolled individuals and compared as the gold standard. NP and saliva samples were collected from 100 rRT-PCR positives and 100 negative individuals and tested with an AQ⁺ kit.

Results

The AQ⁺ kit showed good performances in both NP and saliva samples with an overall accuracy of 98.5% and 94.0%, and sensitivity of 97.0% and 88.0%, respectively. In both cases, specificity was 100%. AQ⁺ kit performance with saliva was in the range of the World Health Organization recommended value.

Conclusion

xOur findings indicate that the saliva specimen can be used as an alternative and less invasive to NPs for quick and reliable SARS-CoV-2 antigen detection.

Test-to-Stay in Kindergarten Through 12th Grade Schools After Household Exposure to Severe Acute Respiratory Syndrome Coronavirus 2

BACKGROUND

Test-to-stay (TTS) is a strategy to limit school exclusion following an exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We evaluated the use of TTS within universally masked kindergarten through 12th grade (K-12) school settings following household SARS-CoV-2 exposure.

METHODS

Three hundred twenty-two participants were enrolled. Serial rapid antigen testing was performed up to 15 days post-exposure. Analysis-eligible participants completed the 15-day testing protocol, tested positive any time during the testing window, or received a negative test on or after day 9. Primary outcomes included within-school tertiary attack rate (TAR) (test positivity among close contacts of positive TTS participants), and school days saved among TTS participants.

RESULTS

Seventy-three of 265 analysis-eligible participants tested positive for SARS-CoV-2 (secondary attack rate of 28% [95% CI: 16-63%]). Among 77 within-school close contacts, 2 were positive (TAR = 3% [95% CI: 1-5%]). Participant absences were limited to 338 days, resulting in 82% of 1849 school days saved.

IMPLICATIONS FOR SCHOOL HEALTH POLICY, PRACTICE, AND EQUITY

TTS facilitates continued in-person learning and can greatly reduce the number of missed school days.

CONCLUSIONS

Within universally masked K-12 schools, TTS is a safe alternative to school exclusion following household SARS-CoV-2 exposure.

Hybridization Chain Reaction Lateral Flow Assays for Amplified Instrument-Free At-Home SARS-CoV-2 Testing

The lateral flow assay format enables rapid, instrument-free, at-home testing for SARS-CoV-2. Due to the absence of signal amplification, this simplicity comes at a cost in sensitivity. Here, we enhance sensitivity by developing an amplified lateral flow assay that incorporates isothermal, enzyme-free signal amplification based on the mechanism of hybridization chain reaction (HCR). The simplicity of the user experience is maintained using a disposable 3-channel lateral flow device to automatically deliver reagents to the test region in three successive stages without user interaction. To perform a test, the user loads the sample, closes the device, and reads the result by eye after 60 min. Detecting gamma-irradiated SARS-CoV-2 virions in a mixture of saliva and extraction buffer, the current amplified HCR lateral flow assay achieves a limit of detection of 200 copies/μL using available antibodies to target the SARS-CoV-2 nucleocapsid protein. By comparison, five commercial unamplified lateral flow assays that use proprietary antibodies exhibit limits of detection of 500 copies/μL, 1000 copies/μL, 2000 copies/μL, 2000 copies/μL, and 20,000 copies/μL. By swapping out antibody probes to target different pathogens, amplified HCR lateral flow assays offer a platform for simple, rapid, and sensitive at-home testing for infectious diseases. As an alternative to viral protein detection, we further introduce an HCR lateral flow assay for viral RNA detection.

Rapid Antigen Tests during the COVID-19 Era in Korea and Their Implementation as a Detection Tool for Other Infectious Diseases

Rapid antigen tests (RATs) are diagnostic tools developed to specifically detect a certain protein of infectious agents (viruses, bacteria, or parasites). RATs are easily accessible due to their rapidity and simplicity. During the COVID-19 pandemic, RATs have been widely used in detecting the presence of the specific SARS-CoV-2 antigen in respiratory samples from suspected individuals. Here, the authors review the application of RATs as detection tools for COVID-19, particularly in Korea, as well as for several other infectious diseases. To address these issues, we present general knowledge on the design of RATs that adopt the lateral flow immunoassay for the detection of the analyte (antigen). The authors then discuss the clinical utilization of the authorized RATs amidst the battle against the COVID-19 pandemic in Korea and their role in comparison with other detection methods. We also discuss the implementation of RATs for other, non-COVID-19 infectious diseases, the challenges that may arise during the application, the limitations of RATs as clinical detection tools, as well as the possible problem solving for those challenges to maximize the performance of RATs and avoiding any misinterpretation of the test result.

Influence of seasonal and operator variations on diagnostic accuracy of lateral flow devices during the COVID-19 pandemic: a systematic review and meta-analysis

BACKGROUND

Lateral flow tests (LFT) are point-of-care rapid antigen tests that allow isolation and control of disease outbreaks through convenient, practical testing. However, studies have shown significant variation in their diagnostic accuracy. We conducted a systematic review of the diagnostic accuracy of LFTs for the detection of severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) to identify potential factors affecting their performance.

METHODS

A systematic search of online databases was carried out to identify studies assessing the sensitivity and specificity of LFTs compared with polymerase chain reaction (PCR) tests. Data were extracted and used to calculate pooled sensitivity and specificity. Meta-regression analysis was conducted to identify covariates influencing diagnostic accuracy.

RESULTS

In total, 76 articles with 108,820 test results were identified for analysis. Pooled sensitivity and specificity were 72% (95% confidence interval (CI): 0.68-0.76) and 100% (95% CI: 0.99-1.00), respectively. Staff operation of the LFT showed a statistically significant increase in sensitivity (p=0.04) and specificity (p=0.001) compared with self-operation by the test subjects. The use of LFTs in symptomatic patient subgroups also resulted in higher test sensitivity.

CONCLUSION

LFTs display good sensitivity and extremely good specificity for SARS-CoV-2 antigen detection; they become more sensitive in patients with symptoms and when performed by trained professionals.

Clinical performance of rapid antigen tests in comparison to RT-PCR for SARS-COV-2 diagnosis in Omicron variant: A systematic review and meta-analysis

The Omicron variant of concern has a high level of mutations in different genes that has raised awareness about the performance of immunological products such as vaccines and antigen detection kits. In this systematic review and meta-analysis, we investigated whether Omicron had a significant influence on rapid antigen test (RAT) performance in comparison to PCR. We registered this systematic review and meta-analysis in PROSPERO with the registration number CRD42022355510. We searched PubMed, Scopus, Embase, and Web of Science databases systematically to 1 August 2022. After article screening, we assessed the quality of the included studies based on the JBI checklist. Following data extraction, we performed a meta-analysis using R software. We included 18 qualified articles presenting sufficient data about RATs performance in comparison to RT-PCR in Omicron infections. The pooled specificity and sensitivity of RATs were 1.000 (0.997-1.000) and 0.671 (0.595-0.721), respectively. The FDA-approved kits showed a better performance than WHO-approved ones with a sensitivity of 0.728 (0.620-0.815). The use of RATs with nasal swabs showed a higher sensitivity compared with nasopharyngeal swabs. The sensitivity for samples with a CT-value >25 was 0.108 (0.048-0.227). Rapid antigen tests show impaired performance for COVID-19 diagnosis when the Omicron variant is circulating, particularly in samples with low viral loads.

Evaluation of the performance of a rapid antigen test (Roche) for COVID-19 diagnosis in an emergency setting in Sweden

During the ongoing COVID-19 pandemic, rapid and reliable detection of SARS-CoV-2 is important to enable proper care of patients and to prevent further transmission. The aim of this study was to evaluate the performance of the Roche SARS-CoV-2 Rapid Antigen Test (Ag-RDT) in an emergency care setting during a high pandemic period. The analytical performance of the Ag-RDT was compared to real-time reverse transcriptase polymerase chain reaction (rRT-PCR). A total of 132 patient samples, previously analyzed with rRT-PCR, were reanalyzed with the Ag-RDT. Tenfold serial dilutions of five different patient strains containing the pangolin variants BA.1, BA.2, B.1.1.7, B.1.160, and B.1.177 were analyzed in parallel with the Ag-RDT and rRT-PCR. A clinical evaluation was performed in which 1911 consecutive patients admitted to the emergency wards in Region Gävleborg, Sweden, were included. Paired samples were collected and analyzed with the Ag-RDT on-site and with rRT-PCR at the microbiology laboratory. The overall sensitivity and specificity of the Ag-RDT in the clinical evaluation were 71.3% and 99.7%, respectively. When samples with cycle threshold (Ct) values above 30 were excluded, the sensitivity was 86.5%. Eleven of the admitted patients who were positive for both the Ag-RDT and rRT-PCR (Ct-range 16.9-30.4) showed no symptoms of COVID-19. Using the Ag-RDT shortened the detection time by an average of 11 h. The Ag-RDT is a useful tool for preliminary screening of SARS-CoV-2 because it enables rapid detection in infectious individuals and therefore, can counteract unnecessary spread of infection at an early stage.

Development and Clinical Evaluation of a Rapid Point of Care Test for Ebola Virus Infection in Humans

The genus Ebolavirus contains multiple species of viruses that are highly contagious and lethal, often causing severe hemorrhagic fever. To minimize the global threat from Ebola virus disease (EVD), sustainable, field-appropriate tools are needed to quickly screen and triage symptomatic patients and conduct rapid screening of cadavers to ensure proper handling of human remains. The OraQuick® Ebola Rapid Antigen Test is an in vitro diagnostic single-use immunoassay for the qualitative detection of Ebola virus antigens that detects all known species within the genus Ebolavirus. Here, we report the performance of the OraQuick® Ebola Rapid Antigen Test and provide a comparison of its performance with other rapid diagnostic tests (RDTs) for EVD. OraQuick® Ebola demonstrated clinical sensitivity of 84.0% in archived EVD patient venous whole-blood (WB) samples, 90.9% in Ebola virus-infected monkey fingerstick samples, and 97.1% in EVD patient cadaver buccal swabs, as well as clinical specificity of 98.0-100% in venous WB samples and 99.1-100% in contrived saliva samples. It is the only 510(k)-cleared Ebola rapid test, has analytical sensitivity as good as or better than all RDT comparators for EVD, and can detect the Sudan virus. Our data demonstrate that the OraQuick® Ebola Rapid Antigen Test is a sensitive and specific assay that can be used for rapid detection of EBOV in humans and could support efforts for EVD-specific interventions and control over outbreaks.

Positive Predictive Value of Rapid Antigen Tests in School During SARS-CoV-2 Omicron Variant Surge

In Korea, we conducted a national observational study to calculate the positive predictive value of SARS-CoV-2 rapid antigen tests in K-12 schools during the Omicron variant surge in March 2022. The weekly positive predictive value ranged from 86.4% to 93.2%. The positive predictive value was the highest among elementary school students with symptoms (95.7%) and lowest among teachers/staff without symptoms (70.9%).

Combined Symptom Screening and At-Home Tests for COVID-19

BACKGROUND AND OBJECTIVE

At-home rapid antigen tests provide a convenient and expedited resource to learn about severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection status. However, low sensitivity of at-home antigen tests presents a challenge. This study examines the accuracy of at-home tests, when combined with computer-facilitated symptom screening.

METHODS

The study used primary data sources with data collected during 2 phases at different periods (phase 1 and phase 2): one during the period in which the alpha variant of SARS-CoV-2 was predominant in the United States and another during the surge of the delta variant. Four hundred sixty-one study participants were included in the analyses from phase 1 and 374 subjects from phase 2. Phase 1 data were used to develop a computerized symptom screening tool, using ordinary logistic regression with interaction terms, which predicted coronavirus disease-2019 (COVID-19) reverse transcription polymerase chain reaction (RT-PCR) test results. Phase 2 data were used to validate the accuracy of predicting COVID-19 diagnosis with (1) computerized symptom screening; (2) at-home rapid antigen testing; (3) the combination of both screening methods; and (4) the combination of symptom screening and vaccination status. The McFadden pseudo-R2 was used as a measure of percentage of variation in RT-PCR test results explained by the various screening methods.

RESULTS

The McFadden pseudo-R2 for the first at-home test, the second at-home test, and computerized symptom screening was 0.274, 0.140, and 0.158, respectively. Scores between 0.2 and 0.4 indicated moderate levels of accuracy. The first at-home test had low sensitivity (0.587) and high specificity (0.989). Adding a second at-home test did not improve the sensitivity of the first test. Computerized symptom screening improved the accuracy of the first at-home test (added 0.131 points to sensitivity and 6.9% to pseudo-R2 of the first at-home test). Computerized symptom screening and vaccination status was the most accurate method to screen patients for COVID-19 or an active infection with SARS-CoV-2 in the community (pseudo-R2 = 0.476).

CONCLUSION

Computerized symptom screening could either improve, or in some situations, replace at-home antigen tests for those individuals experiencing COVID-19 symptoms.

Performance Evaluation of STANDARD Q COVID/FLU Ag Combo for Detection of SARS-CoV-2 and Influenza A/B

We evaluated the performance of the STANDARD Q COVID/FLU Ag Combo test (Q Ag combo test) for the detection of SARS-CoV-2, influenza A, and influenza B using a single point-of-care device compared with real-time PCR. A total of 408 individuals, 55 positives with SARS-CoV-2, 90 with influenza A, 68 with influenza B, and 195 negatives for all viruses, participated. The Q Ag combo test demonstrated a high level of sensitivity of 92.73% and a specificity of 99.49% for the detection of SARS-CoV-2. When the number of days from symptom onset (DSO) was restricted to 0 < DSO ≤ 6, the sensitivity of the Q Ag combo test to detect SARS-CoV-2 was 100%, and when the Ct value of RdRp was ≤20, the sensitivity to detect SARS-CoV-2 was 93.10%. The Q Ag combo test results also demonstrated a sensitivity of 92.22% and a specificity of 100% for influenza A, a sensitivity of 91.18%, and a specificity of 99.49% for influenza B. The agreement analysis of the Q Ag combo test with the RT-PCR results demonstrated excellent outcomes, making it useful and efficient for the detection of SARS-CoV-2, influenza A, and influenza B.

A diagnostic accuracy study comparing RNA LAMP, direct LAMP, and rapid antigen testing from nasopharyngeal swabs

Introduction

During the coronavirus disease 2019 (COVID-19) pandemic, the early detection and isolation of individuals infected with severe acute respiratory syndrome coronavirus disease 2 (SARS-CoV-2) through mass testing can effectively prevent disease transmission. SARS-CoV-2 nucleic acid rapid detection based on loop-mediated isothermal amplification (LAMP) may be appropriate to include in testing procedures.

Methods

We used 860 nasopharyngeal specimens from healthcare workers of Huashan Hospital and COVID-19 patients collected from April 7th to 21st, 2022, to assess the clinical diagnostic performance of the LAMP assay marketed by Shanghai GeneSc Biotech and compared it to the result of a rapid antigen test (RAT) head-to-head.

Results

Overall, the diagnostic performance of LAMP assay and RAT were as follows. The LAMP assay represented higher sensitivity and specificity than RAT, especially in the extracted RNA samples. The sensitivity was 70.92% and 92.91% for direct LAMP and RNA-LAMP assay, respectively, while the specificity was 99.86% and 98.33%. The LAMP assay had overall better diagnostic performance on the specimens with relatively lower C _t values or collected in the early phase (≤7 days) of COVID-19. The combination of LAMP assay and RAT improved diagnostic efficiency, providing new strategies for rapidly detecting SARS-CoV-2.

Conclusion

The LAMP assay are suitable for mass screenings of SARS-CoV-2 infections in the general population.

A Comparison Study of the Detection Limit of Omicron SARS-CoV-2 Nucleocapsid by Various Rapid Antigen Tests

Rapid antigen tests (RATs) are widely used worldwide to detect SARS-CoV-2 since they are an easy-to-use kit and offer rapid results. The RAT detects the presence of the nucleocapsid protein, which is located inside the virus. However, the sensitivity of the different RATs varies between commercially available kits. The test result might change due to various factors, such as the variant type, infection date, swab's surface, the manner in which one performs the testing and the mucus components. Here, we compare the detection limit of seven commercially available RATs by introducing them to known SARS-CoV-2 nucleocapsid protein amounts from the Omicron variant. It allows us to determine the detection limit, disregarding the influences of other factors. A lower detection limit of the RAT is necessary since earlier detection will help reduce the spread of the virus and allow faster treatment, which might be crucial for the population at risk.

Impacts of social distancing, rapid antigen test and vaccination on the Omicron outbreak during large temperature variations in Hong Kong: a modelling study

Background

The impacts of non-pharmaceutical interventions (NPIs) and vaccine boosters on the transmission of the largest outbreak of COVID-19 (the fifth wave) in Hong Kong have not been reported. The outbreak, dominated by the Omicron BA.2 subvariant, began to spread substantially after the Spring Festival in February, 2022, when the temperature varied greatly (e.g. a cold surge event). Tightening social distancing measures did not succeed in containing the outbreak until later with the use of rapid antigen tests (RAT) and increased vaccination rates. Temperature has been previously found to have significant impact on the transmissibility. Understanding how the public health interventions influence the number of infections in this outbreak provide important insights on prevention and control of COVID-19 during different seasons.

Methods

We developed a transmission model incorporating stratified immunity with vaccine-induced antibody responses and the daily changes in population mobility, vaccination and weather factors (i.e. temperature and relative humidity). We fitted the model to the daily reported cases detected by either PCR or RAT between 1 February and 31 March using Bayesian statistics, and quantified the effects of individual NPIs, vaccination and weather factors on transmission dynamics.

Results

Model predicted that, with the vaccine uptake, social distancing reduced the cumulative incidence (CI) from 58.2% to 44.5% on average. The use of RAT further reduced the CI to 39.0%. Without vaccine boosters in these two months, the CI increased to 49.1%. While public health interventions are important in reducing the total infections, the outbreak was temporarily driven by the cold surge. If the coldest two days (8.5 °C and 8.8 °C) in February were replaced by the average temperature in that month (15.2 °C), the CI would reduce from 39.0% to 28.2%.

Conclusion

Preventing and preparing for the transmission of COVID-19 considering the change in temperature appears to be a cost-effective preventive strategy to lead people to return to normal life.

COVID-19 breakthrough infections in vaccinated participants of the Safety and Efficacy of Preventative COVID Vaccines sub-study

BACKGROUND

The rate of breakthrough infection in vaccinated Ontarians during the Omicron wave is unknown.

METHODS

Active participants of the Safety and Efficacy of Preventative COVID Vaccines (STOPCoV) study (892 ≥age 70 years and 369 aged 30-50 years) were invited to participate in a sub-study evaluating breakthrough COVID-19 infection. Self-administered rapid antigen tests (RAT) were reported twice weekly and symptom questionnaires weekly for 6 weeks. The primary outcome was the proportion reporting a positive RAT.

RESULTS

A total of 806 e-consented, and 727 (90%) completed ≥1 RAT, with total 7,116 RATs completed between January 28 and March 29, 2022. Twenty out of twenty-five participants with a positive RAT had a booster vaccine prior to the positive test. All cases were mild, none requiring hospitalization. Nineteen had positive dried blood spot analysis for IgG antibody to the receptor binding domain (RBD) prior to the positive RAT. The mean normalized IgG ratio to RBD was 1.22 (SD 0.29) for younger and 0.98 (SD 0.44) for older participants, values similar to corresponding ratios for those without positive RATs and those in the main cohort. One hundred and five participants reported one and 96 reported ≥2 possible COVID-19 symptoms despite negative RATs. The false negative RAT was low (4% to 6.6 %) compared with subsequent positive nucleoprotein antibody.

CONCLUSIONS

Positive RAT for COVID-19 was infrequent (3.4%). We were unable to determine a protective antibody level against breakthrough infection. Our findings can inform public health COVID-19 restrictions guidelines. Our decentralized study provides a model for rapid institution of new questions during a pandemic.

Sensitivity analysis of rapid antigen tests for the Omicron SARS-CoV-2 variant detection from nasopharyngeal swab samples collected in Santiago of Chile

The COVID-19 pandemic continues to be a concern and keeps global health authorities on alert. The RT-PCR technique has been the gold-standard assay for detecting the SARS-CoV-2 virus. However, rapid antigen tests (RATs) have been widely used to increase the number of tests faster and more efficiently in the population. Nevertheless, the appearance of new viral variants, with genomic mutations associated with greater contagiousness and immune evasion, highlights the need to evaluate the sensitivity of these RATs. This report evaluates the sensitivity of SD Biosensor-Roche, Panbio™, and Clinitest® RATs widely used in Santiago de Chile in the detection of the Omicron variant from Nasopharyngeal samples (NPSs), the most predominant SARS-CoV-2 variant in Chile and the world. SD Biosensor-Roche shows a detection sensitivity of 95.7% in the viral amplification range of 20 ≤ Cq < 25, while Panbio™ and Clinitest® show 100% and 91.3%, respectively. In the viral amplification ranges of 25 ≤ Cq < 30, the detection sensitivity decreased to 28% for SD Biosensor-Roche, 32% for Panbio™, and 72% for Clinitest®. This study indicates that the tested RATs have high sensitivity in detecting the Omicron variant of concern (VOC) at high viral loads. By contrast, its sensitivity decreases at low viral loads. Therefore, it is suggested to limit the use of RATs as an active search method, considering that infections in patients are increasingly associated with lower viral loads of SARS-CoV-2. These antecedents could prevent contagion outbreaks and reduce the underestimation of the current Omicron variant circulation at the local level.

COVID-19 Rapid Antigen Tests: Bibliometric Analysis of the Scientific Literature

As the COVID-19 pandemic continues to disrupt health systems worldwide, conducting Rapid Antigen Testing (RAT) at specified intervals has become an essential part of many people's lives around the world. We identified and analyzed the academic literature on COVID-19 RAT. The Web of Science electronic database was queried on 6 July 2022 to find relevant publications. Publication and citation data were retrieved directly from the database. VOSviewer, a bibliometric software, was then used to relate these data to the semantic content from the titles, abstracts, and keywords. The analysis was based on data from 1000 publications. The most productive authors were from Japan and the United States, led by Dr. Koji Nakamura from Japan (n = 10, 1.0%). The most academically productive countries were in the North America, Europe and Asia, led by the United States of America (n = 266, 26.6%). Sensitivity (n = 32, 3.2%) and specificity (n = 23, 2.3%) were among the most frequently recurring author keywords. Regarding sampling methods, "saliva" (n = 54, 5.4%) was mentioned more frequently than "nasal swab" (n = 32, 3.2%) and "nasopharyngeal swab" (n = 22, 2.2%). Recurring scenarios that required RAT were identified: emergency department, healthcare worker, mass screening, airport, traveler, and workplace. Our bibliometric analysis revealed that COVID-19 RAT has been utilized in a range of studies. RAT results were cross-checked with RT-PCR tests for sensitivity and specificity. These results are consistent with comparable exchanges of methods, results or discussions among laboratorians, authors, institutions and publishers in the involved countries of the world.

Characterization of SARS-CoV-2 Omicron variant shedding and predictors of viral culture positivity on vaccinated healthcare workers with mild COVID-19

In this prospective cohort of 30 vaccinated healthcare workers with mild Omicron variant infection, we evaluated viral culture, rapid antigen test (RAT), and real-time reverse-transcription polymerase chain reaction (RT-PCR) of respiratory samples at days 5, 7, 10, and 14. Viral culture was positive in 46% (11/24) and 20% (6/30) of samples at days 5 and 7, respectively. RAT and RT-PCR (Ct ≤35) showed 100% negative predictive value (NPV), with positive predictive values (PPVs) of 32% and 17%, respectively, for predicting viral culture positivity. A lower RT-PCR threshold (Ct ≤24) improved culture prediction (PPV = 39%; NPV = 100%). Vaccinated persons with mild Omicron infection are potentially transmissible up to day 7. RAT and RT-PCR might be useful tools for shortening the isolation period.

Point of care molecular and antigen detection tests for COVID-19: current status and future prospects

INTRODUCTION

Detection of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) has been critical to support and management of the COVID-19 pandemic. Point of care testing (POCT) for SARS-CoV-2 has been a widely used tool for detection of SARS-CoV-2.

AREAS COVERED

POCT nucleic acid amplification tests (NAATs) and rapid antigen tests (RATs) have been the most readily used POCT for SARS-CoV-2. Here, current knowledge on the utility of POCT NAATs and RATs for SARS-CoV-2 are reviewed and discussed alongside aspects of quality assurance factors that must be considered for successful and safe implementation of POCT.

EXPERT OPINION

Use cases for implementation of POCT must be evidence based, regardless of the test used. A quality assurance framework must be in place to ensure accuracy and safety of POCT.

SARS-CoV-2 Virus Culture, Genomic and Subgenomic RNA Load, and Rapid Antigen Test in Experimentally Infected Syrian Hamsters

The duration of SARS-CoV-2 genomic RNA shedding is much longer than that of infectious SARS-CoV-2 in most COVID-19 patients. It is very important to determine the relationship between test results and infectivity for efficient isolation, contact tracing, and post-isolation. We characterized the duration of viable SARS-CoV-2, viral genomic and subgenomic RNA (gRNA and sgRNA), and rapid antigen test positivity in nasal washes, oropharyngeal swabs, and feces of experimentally infected Syrian hamsters. The duration of viral genomic RNA shedding is longer than that of viral subgenomic RNA, and far longer than those of rapid antigen test (RAgT) and viral culture positivity. The rapid antigen test results were strongly correlated with the viral culture results. The trend of subgenomic RNA is similar to that of genomic RNA, and furthermore, the subgenomic RNA load is highly correlated with the genomic RNA load. IMPORTANCE Our findings highlight the high correlation between rapid antigen test and virus culture results. The rapid antigen test would be an important supplement to real-time reverse transcription-RCR (RT-PCR) in early COVID-19 screening and in shortening the isolation period of COVID-19 patients. Because the subgenomic RNA load can be predicted from the genomic RNA load, measuring sgRNA does not add more benefit to determining infectivity than a threshold determined for gRNA based on viral culture.

Comparison of the SARS-CoV-2 BD Veritor Nasal Antigen Test with Nasopharyngeal Reverse Transcription-PCR in Symptomatic Patients

This study evaluated the BD Veritor system for rapid detection of SARS-CoV-2, an immunochromatographic point-of-care test, by comparing it with a standard reverse transcription-PCR (RT-PCR) methodology using samples from symptomatic patients. Samples from 146 symptomatic and 2 asymptomatic patients between the 1st and the 40th day of infection were evaluated. The nasopharyngeal and/or oropharyngeal swabs were inserted in a tube containing 0.9% saline solution and stored at refrigerator temperature until the moment of use. The samples were first tested with the Xpert Xpress SARS-CoV-2 (GeneXpert) kit (RT-PCR method), and the cycle thresholds (C_Ts) for the E and N2 genes encoding the SARS-CoV-2 envelope and nucleoprotein, respectively, were established. Subsequently, the same samples were tested using the Veritor rapid test. We analyzed the C_Ts of the N2 gene, which is detected in both methodologies, and observed sensitivities of 100%, 98.8%, 89.6%, and 82.7% for the C_Ts of <25, <27, and <30 and all the C_Ts, respectively. The greatest sensitivity was observed when we performed the test on patients within 5 days of symptom onset. The BD Veritor system’s workflow is simple and fast, taking approximately 16 min from sample preparation to obtaining the test result. In addition to its satisfactory sensitivity, with results that correlate with those of the RT-PCR, the BD Veritor analyzer instrument reduces the subjectivity of unaided visual readings and consequent potential variation in result interpretation. Therefore, our results showed that the BD Veritor diagnostic test can provide a rapid and accurate diagnosis for SARS-CoV-2.

IMPORTANCE This study provides important and useful information, especially for diagnostic laboratories, since the results show that the BD Veritor system can provide a fast and safe point-of-care antigen diagnostic test for rapid detection of COVID-19 that has high sensitivity, reproducibility, and accuracy.

Persistence of Severe Acute Respiratory Syndrome Coronavirus 2 Omicron Variant in Children and Utility of Rapid Antigen Testing as an Indicator of Culturable Virus

We screened 65 longitudinally collected nasal swab samples from 31 children aged 0-16 years who were positive for severe acute respiratory syndrome coronavirus 2 Omicron BA.1. By day 7 after onset of symptoms, 48% of children remained positive by rapid antigen test. In a sample subset, we found 100% correlation between antigen test results and virus culture.

Role of population and test characteristics in antigen-based SARS-CoV-2 diagnosis, Czechia, August to November 2021

Background

Analyses of diagnostic performance of SARS-CoV-2 antigen rapid diagnostic tests (AG-RDTs) based on long-term data, population subgroups and many AG-RDT types are scarce.

Aim

We aimed to analyse sensitivity and specificity of AG-RDTs for subgroups based on age, incidence, sample type, reason for test, symptoms, vaccination status and the AG-RDT’s presence on approved lists.

Methods

We included AG-RDT results registered in Czechia’s Information System for Infectious Diseases between August and November 2021. Subpopulations were analysed based on 346,000 test results for which a confirmatory PCR test was recorded ≤ 3 days after the AG-RDT; 38 AG-RDTs with more than 100 PCR-positive and 300 PCR-negative samples were individually evaluated.

Results

Average sensitivity and specificity were 72.4% and 96.7%, respectively. We recorded lower sensitivity for age groups 0–12 (65.5%) and 13–18 years (65.3%). The sensitivity level rose with increasing SARS-CoV-2 incidence from 66.0% to 76.7%. Nasopharyngeal samples had the highest sensitivity and saliva the lowest. Sensitivity for preventive reasons was 63.6% vs 86.1% when testing for suspected infection. Sensitivity was 84.8% when one or more symptoms were reported compared with 57.1% for no symptoms. Vaccination was associated with a 4.2% higher sensitivity. Significantly higher sensitivity levels pertained to AG-RDTs on the World Health Organization Emergency Use List (WHO EUL), European Union Common List and the list of the United Kingdom’s Department of Health and Social Care.

Conclusion

AG-RDTs from approved lists should be considered, especially in situations associated with lower viral load. Results are limited to SARS-CoV-2 delta variant.

Evaluation of the performance of Panbio™ COVID-19 antigen rapid diagnostic test for the detection of SARS-CoV-2 in suspected patients in Ethiopia

Objective:

Reverse transcription-polymerase chain reaction is a gold standard diagnostic tool for coronavirus disease-2019. Limited coverage and long turnaround times are linked to the poor response to the pandemic in developing countries like Ethiopia. To overcome the challenges, rapid antigen diagnostic kits are recommended if their diagnostic performance is at an acceptable level. We explored the performance of the Panbio™ coronavirus disease-2019 antigen rapid diagnostic test in diagnosing the coronavirus disease-2019 infection.

Methods:

A cross-sectional study was conducted on coronavirus disease-2019 suspected patients in Wollega University Referral Hospital, from 1 April to 30 May 2021. After obtaining consent/ assent, sociodemographic and pair of nasopharyngeal samples were collected from each and examined by Panbio antigen rapid diagnostic test and reverse transcription-polymerase chain reaction. Data were entered and analysed using SPSS version 24. Sensitivity, specificity, positive and negative predictive values, and kappa values were calculated.

Results:

A total of 148 coronavirus disease-2019 suspected individuals (54.1% male) participated in the study. Of all, 73 (49.3%) were positive for severe acute respiratory syndrome corona virus by reverse transcription-polymerase chain reaction test. The sensitivity and specificity of Panbio were found 81% (95% confidence interval: 71%–91%) and 98.7% (95% confidence interval: 96%–100%), respectively. From 75 negative and 73 positive samples by reverse transcription-polymerase chain reaction, 1 (1.33%) and 14 (19.18%) were found false positive and negative by antigen rapid diagnostic test, respectively. Positive predictive value and negative predictive value of Panbio were 98.3% and 84.1%, respectively, and test agreement was substantial (kappa value = 0.80).

Conclusion:

Panbio has fine performance in suspected patients. Further studies are needed to examine the accuracy of self-collecting and patient self-testing with healthcare workers, using antigen rapid diagnostic test against the reference standard.

Diagnostic Performance of the Rapid Antigen Test as a Screening Tool for SARS-CoV-2 Infection in the Emergency Department

The rapid antigen test (RAT) has been adopted as a screening tool for SARS-CoV-2 infection in many emergency departments (EDs). We aimed to investigate the diagnostic value of the accuracy of the SARS-CoV-2 RAT as a screening tool in the ED. This retrospective observational study included patients who underwent both RAT and RT−PCR and visited the ED from 1 December 2021 to 15 March 2022. RAT and RT−PCR were performed by appropriately trained physicians. We performed detailed analyses using the E gene cyclic threshold (Ct) values of RT−PCR. Out of a total of 1875 patients, 348 (18.6%) had positive and 1527 (81.4%) had negative RT−PCR results. The overall sensitivity, specificity, positive predictive value, and negative predictive value of the RAT were 67.8%, 99.9%, 99.6%, and 93.2%, respectively. The E gene Ct value was significantly lower in the RAT-positive patients than in the RAT-negative patients (18.5 vs. 25.3, p < 0.001). When the E gene Ct cutoff was 30.0, 25.0, 20.0, and 15.0, the sensitivity of the RAT was 71.9%, 80.3%, 93.0%, and 97.8%, respectively. The sensitivity of the RAT could be considered high in patients with a high viral load, and the RAT could be used as a screening tool in the ED.

Progression of LAMP as a Result of the COVID-19 Pandemic: Is PCR Finally Rivaled?

Reflecting on the past three years and the coronavirus disease 19 (COVID-19) pandemic, varying global tactics offer insights into the most effective public-health responses. In the US, specifically, rapid and widespread testing was quickly prioritized to lower restrictions sooner. Essentially, only two types of COVID-19 diagnostic tests were publicly employed during the peak pandemic: the rapid antigen test and reverse transcription polymerase chain reaction (RT-PCR). However, neither test ideally suited the situation, as rapid antigen tests are far too inaccurate, and RT-PCR tests require skilled personnel and sophisticated equipment, leading to long wait times. Loop-mediated isothermal amplification (LAMP) is another exceptionally accurate nucleic acid amplification test (NAAT) that offers far quicker time to results. However, RT-LAMP COVID-19 tests have not been embraced as extensively as rapid antigen tests or RT-PCR. This review will investigate the performance of current RT-LAMP-based COVID-19 tests and summarize the reasons behind the hesitancy to embrace RT-LAMP instead of RT-PCR. We will also look at other LAMP platforms to explore possible improvements in the accuracy and portability of LAMP, which could be applied to COVID-19 diagnostics and future public-health outbreaks.

Clinical Performance of Rapid and Point-of-Care Antigen Tests for SARS-CoV-2 Variants of Concern: A Living Systematic Review and Meta-Analysis

Rapid antigen tests (RATs) for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are widely used in the Coronavirus disease 2019 (COVID-19) pandemic caused by diverse variants. Information on the real-world performance of RATs for variants is urgently needed for decision makers. Systematic searches of the available literature and updates were conducted in PubMed, Ovid-MEDLINE, Ovid-EMBASE, CENTRAL, and KMBASE for articles evaluating the accuracy of instrument-free RATs for variants up until 14 March 2022. A bivariate random effects model was utilized to calculate pooled diagnostic values in comparison with real-time reverse transcription-polymerase chain reaction as the reference test. A total of 7562 samples from six studies were available for the meta-analysis. The overall pooled sensitivity and specificity of RATs for variants were 69.7% (95% confidence interval [CI] = 62.5% to 76.1%) and 100.0% (95% CI = 98.8% to 100.0%), respectively. When an additional 2179 samples from seven studies reporting sensitivities only were assessed, the pooled sensitivity dropped to 50.0% (95% CI = 44.0% to 55.0%). These findings suggest reassessment and monitoring of the diagnostic utility of RATs for variants, especially for the sensitivity aspect, to facilitate appropriate diagnosis and management of COVID-19 patients.

Testing Frequency Matters: An Evaluation of the Diagnostic Performance of a Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Rapid Antigen Test in US Correctional Facilities

BACKGROUND

The Centers for Disease Control and Prevention recommends serial rapid antigen assay collection within congregate facilities. Although modeling and observational studies from communities and long-term care facilities have shown serial collection provides adequate sensitivity and specificity, the accuracy within correctional facilities remains unknown.

METHODS

Using Connecticut Department of Correction data from 21 November 2020 to 15 June 2021, we estimated the accuracy of a rapid assay, BinaxNOW (Abbott), under 3 collection strategies: single test collection and serial collection of 2 and 3 tests separated by 1-4 days. The sensitivity and specificity of the first (including single), second, and third serially collected BinaxNOW tests were estimated relative to RT-PCRs collected ≤1 day of the BinaxNOW test. The accuracy metrics of the testing strategies were then estimated as the sum (sensitivity) and product (specificity) of tests in each strategy.

RESULTS

Of the 13 112 residents who contributed ≥1 BinaxNOW test during the study period, 3825 contributed ≥1 RT-PCR paired BinaxNOW test. In relation to RT-PCR, the 3-rapid-antigen-test strategy had a sensitivity of 95.9% (95% CI: 93.6-97.5%) and specificity of 98.3% (95% CI: 96.7-99.1%). The sensitivities of the 2- and 1-rapid-antigen-test strategies were 88.8% and 66.8%, and the specificities were 98.5% and 99.4%, respectively. The sensitivity was higher among symptomatic residents and when RT-PCRs were collected before BinaxNOW tests.

CONCLUSIONS

We found serial antigen test collection resulted in high diagnostic accuracy. These findings support serial collection for outbreak investigation, screening, and when rapid detection is required (such as intakes or transfers).

An Agreement of Antigen Tests on Oral Pharyngeal Swabs or Less Invasive Testing With Reverse Transcription Polymerase Chain Reaction for Detecting SARS-CoV-2 in Adults: Protocol for a Prospective Nationwide Observational Study

Background

The SARS-CoV-2 pandemic has resulted in an unprecedented level of worldwide testing for epidemiologic and diagnostic purposes, and due to the extreme need for tests, the gold-standard Reverse Transcription Polymerase Chain Reaction (RT-PCR) testing capacity has been unable to meet the overall worldwide testing demand. Consequently, although the current literature has shown the sensitivity of rapid antigen tests (RATs) to be inferior to RT-PCR, RATs have been implemented on a large scale without solid data on performance.

Objective

This study will compare analytical and clinical sensitivities and specificities of 50 lateral flow– or laboratory-based RATs and 3 strand invasion–based amplification (SIBA)-RT-PCR tests from 30 manufacturers to RT-PCR testing of samples obtained from the deep oropharynx. In addition, the study will compare sensitivities and specificities of the included RATs as well as RT-PCR on clinical samples obtained from the deep oropharynx, the anterior nasal cavity, saliva, the deep nasopharynx, and expired air to RT-PCR on deep oropharyngeal samples.

Methods

In the prospective part of the study, 200 individuals found SARS-CoV-2 positive and 200 individuals found SARS-CoV-2 negative by routine RT-PCR testing will be retested with each RAT, applying RT-PCR as the reference method. In the retrospective part of the study, 304 deep oropharyngeal cavity swabs divided into 4 groups based on RT-PCR quantification cycle (Cq) levels will be tested with each RAT.

Results

The results will be reported in several papers with different aims. The first paper will report retrospective (analytical sensitivity, overall and stratified into different Cq range groups) and prospective (clinical sensitivity) data for RATs, with RT-PCR as the reference method. The second paper will report results for RAT based on anatomical sampling location. The third paper will compare different anatomical sampling locations by RT-PCR testing. The fourth paper will focus on RATs that rely on central laboratory testing. Tests from 4 different manufacturers will be compared for analytical performance data on retrospective deep oropharyngeal swab samples. The fifth paper will report the results of 4 RATs applied both as professional use and as self-tests. The last paper will report the results from 2 breath tests in the study. A comparison of sensitivity and specificity between RATs will be conducted using the McNemar test for paired samples and the chi-squared test for unpaired samples. Comparison of the positive predictive value (PPV) and negative predictive value (NPV) between RATs will be performed by the bootstrap test, and 95% CIs for sensitivity, specificity, PPV, and NPV will be calculated as bootstrap CIs.

Conclusions

The study will compare the sensitivities of a large number of RATs for SARS-CoV-2 to with those of RT-PCR and will address whether lateral flow–based RATs differ significantly from laboratory-based RATs. The anatomical test locations for both RATs and RT-PCR will also be compared.

Trial Registration

ClinicalTrials.gov NCT04913116; https://clinicaltrials.gov/ct2/show/NCT04913116

International Registered Report Identifier (IRRID)

DERR1-10.2196/35706

Halo-A Universal Fluorescence Reader Based Threat Agent Detection Platform-A Proof of Concept Study Using SARS-CoV-2 Assays

Polymerase chain reaction (PCR) remains the gold standard in disease diagnostics due to its extreme sensitivity and specificity. However, PCR tests are expensive and complex, require skilled personnel and specialized equipment to conduct the tests, and have long turnaround times. On the other hand, lateral flow immunoassay-based antigen tests are rapid, relatively inexpensive, and can be performed by untrained personnel at the point of care or even in the home. However, rapid antigen tests are less sensitive than PCR since they lack the inherent target amplification of PCR. It has been argued that rapid antigen tests are better indicators of infection in public health decision-making processes to test, trace, and isolate infected people to curtail further transmission. Hence, there is a critical need to increase the sensitivity of rapid antigen tests and create innovative solutions to achieve that goal. Herein, we report the development of a low-cost diagnostic platform, enabling rapid detection of SARS-CoV-2 under field or at-home conditions. This platform (Halo™) is a small, highly accurate, consumer-friendly diagnostic reader paired with fluorescently labeled lateral flow assays and custom software for collection and reporting of results. The focus of this study is to compare the analytical performance of Halo^TM against comparable tests that use either colloidal gold nanoparticles or fluorescence-based reporters in simulated nasal matrix and not in clinical samples. Live virus data has demonstrated limit of detection performance of 1.9 TCID₅₀/test in simulated nasal matrix for the delta variant, suggesting that single-assay detection of asymptomatic SARS-CoV-2 infections may be feasible. Performance of the system against all tested SARS CoV-2 virus variants showed comparable sensitivities indicating mutations in SARS-CoV-2 variants do not negatively impact the assay.

Ophthalmology practice in COVID-19 pandemic: Performance of rapid antigen test versus real time-reverse transcription polymerase chain reaction in a tertiary eye care institute in South India

Purpose:

To assess the rapid antigen test (RAT) against the gold standard reverse transcription-polymerase chain reaction (RT-PCR) to screen COVID-19 infection in asymptomatic patients undergoing ophthalmic procedures.

Methods:

This was a retrospective hospital-based study. Point-of-care (PoC) RAT was performed using nasopharyngeal swab, while RT-PCR for SARS-CoV-2 viral RNA was performed using both nasopharyngeal and throat swabs.

Results:

A total of 629 patients were tested for SARS-CoV-2 by using both RAT and RT-PCR. Only one patient had tested positive for SARS-CoV-2 with both RAT and RT-PCR, while two patients had tested positive with RT-PCR after an initial negative RAT. The positivity rate for RAT was 0.15% (1/629), and that for RT-PCR was 0.47%. Percent agreement or proportion of agreement observed between the two tests was 99.68%, while Cohen’s kappa coefficient value was 0.49. The sensitivity of RAT in comparison to RT-PCR was 33.33%, specificity was 100%, positive predictive value was 100%, and negative predictive value was 99.68%.

Conclusion:

The sensitivity and Cohen’s kappa coefficient in our study were low but that can be attributed to the overall low positivity rates with both RAT and RT-PCR. However, percent agreement observed between the two tests was very high. Therefore, we recommend initial screening of all the patients for COVID-19 symptoms followed by RAT before performing any ophthalmic surgical procedure to ensure the safety of the health care professionals as well as the patients.