Evaluation of a rapid antigen test using a point of care real-time RT-PCR as a comparator for the detection of SARS-CoV-2

COVID-19 rapid antigen testing strategies require careful evaluation

SARS-CoV-2 rapid antigen detection tests

The disease caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was named as coronavirus disease-2019 (COVID-19) by the World Health Organization (WHO) in February 11, 2020. The rapid diagnosis of COVID-19 patients is essential to reduce the disease spread. The reverse-transcription polymerase chain reaction (RT-PCR) is the gold standard test to diagnose SARS-CoV-2 acute infection. The rapid antigen test which can detect the presence of viral protein antigens in respiratory tract samples is being investigated as an alternative option, especially in cases where RT-PCR is not available or the test capacity is exceeded, due to its faster results, ease of application, low cost and lack of special equipment and personnel. In this study, it was aimed to evaluate the performance of a commercial rapid antigen test using nasopharyngeal samples of COVID-19 patients confirmed with RT-PCR. From the first day of the research, the first 80 consecutively SARS-CoV-2 RT-PCR positive and 40 RT-PCR negative respiratory samples sent to the Medical Microbiology Laboratory for routine SARS-CoV-2 RT-PCR testing were included in the study. RT-PCR tests of the samples were performed in routine studies with the BioSpeedy SARS-CoV-2 RT-PCR kit (Bioeksen, Turkey). Rapid antigen tests were performed with the Wesail COVID-19 antigen test kit (Guangdong, China) simultaneously with RT-PCR tests. Amongst the 80 positive RT-PCR samples, 56 were detected by the rapid antigen test. All the samples detected as positive with the rapid antigen tests were also positive with RT-PCR. There was a moderate agreement between the qualitative results of both tests (Kappa= 0.609, p<0.001). According to the PCR test, the sensitivity, specificity, positive predictive value (PPV), negative predictive value, and accuracy of the rapid antigen test were; 70%, 100%, 100%, 62.5%, and 80% (96/120), respectively. The sensitivities of the rapid antigen test were calculated as 92.6% in 54 samples with a cycle threshold (Ct) value of <17, 88.7% in 62 samples with a Ct value of <20, 77.8% in 72 samples with a Ct value of <22, and 74.7% in 75 samples with a Ct value of <25. According to our study data; the rapid antigen test was found less sensitive than the RT-PCR test. Negative results obtained with rapid antigen testing cannot exclude SARS-CoV-2 infection and must be confirmed by RT-PCR. In addition, according to the ROC analysis of rapid antigen test positivity obtained according to RT-PCR Ct values, the clinical performance of the rapid antigen test is good in samples with Ct values <20. The rapid antigen test should be evaluated as a reliable screening test in patients with high viral load. To the best of our knowledge, there is no other study in the literature performed with the Wesail COVID-19 rapid antigen test kit (Guangdong, China) used in our study. The fact that PPV was found to be 100% even at a low prevalence period of the pandemic will enable positive patients to be screened quickly and effectively with rapid antigen tests in the first step during the high prevalence period of the pandemic. In the light of these data and our results, it can be predicted that using the rapid antigen test as a screening test in the first step and confirming only negative patients with RT-PCR will contribute to the effective management of the pandemic process in terms of both time and cost. As a result of the study, the rapid antigen test with low sensitivity but high PPD can be included as a facilitating test in the first step of the diagnostic algorithm in terms of rapid identification of the patients with high viral load, initiation of treatment and providing filiation.

Point-of-care evaluation of a rapid antigen test (CLINITESTⓇ Rapid COVID-19 Antigen Test) for diagnosis of SARS-CoV-2 infection in symptomatic and asymptomatic individuals

Severe acute respiratory syndrome coronavirus 2 screening to augment dental office and patient safety

Information on the use of antigen-based SARS-CoV-2 rapid antigen tests (RAT) in children is limited. RATs have been used more frequently, because they are easily applicable, inexpensive, and can be easily performed at home without the need for special equipment. This study was designed to assign the diagnostic test accuracy of the SARS-CoV-2 RAT in daily clinical practice in children. One thousand forty-two pediatric patients (aged 1 month - 18 years) who presented to the pediatric COVID-19 outpatient clinic of our hospital between January 2021 and June 2022 and met the inclusion criteria were included in this study. Nasopharyngeal samples were taken from the patients at the same visit, first for reverse transcription polymerase chain reaction (RT-PCR) and then for RAT. The data of all patients with RT-PCR positivity (n = 314) and additionally 14 patients with RAT positivity were analyzed in depth. The overall sensitivity and specificity were 62.1% (95% CI: 56.4 - 67.4) and 98% (95% CI: 96.7 - 98.9), respectively. The positive predictive value (PPV) and the negative predictive value (NPV) in this pediatric study were 93.3% and 85.7% (95% CI: 88.7 - 96.1 and 83.1 - 87.9), respectively. Considering the Ct values, which are indirect indicators of viral load, it was observed that the sensitivity of the rapid antigen test increased at low Ct values. The sensitivity increased to 75.1% (95% CI: 67.9 - 81.1) in patients with a Ct value of < 25. The specificity was 92.7% (95% CI: 90.7 - 94.3), PPV was 67.8% (95% CI: 60.7 - 67.8) and the NPV was 94.7% (95% CI: 93.0 - 96.1) in patients with a Ct value < 25. When the patients were evaluated according to their symptomatic/asymptomatic status, the difference between the diagnostic performance of the RAT test was found to be statistically significant (p = 0.006). In our study, it was found that the sensitivity of RATs in pediatric patients was lower than in adults. Our results also showed that children are not small adults, and the sensitivity of the test was higher, especially in symptomatic patients and patients with high viral load. To obtain more accurate results, we believe that performing the test in the first 3 days of symptoms will give more accurate results.

We assessed the performance of the Panbio rapid antigen detection (RAD) test for the detection of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection and we compared it with the routine reverse transcriptase‐polymerase chain reaction (RT‐PCR)‐based molecular test in a population of 4167 unselected patients admitted to IRCCS Sacro Cuore Don Calabria Hospital. Analysis stratified by cycling threshold (C t) value of SARS‐CoV‐2 gene targets indicated that antigen (Ag)‐positive C t values were significantly lower compared to Ag‐negative values (p < 0.0001). Overall, we found discordance in 140, tested negative by RAD and positive by RT‐PCR, and in 4 resulted positive by RAD and negative by RT‐PCR. RAD test achieved a sensitivity and specificity of 66.82% and 99.89%, respectively. The positive predictive value was shown to be 97.87% while the negative predictive value was shown to be 97.62%. In our context, the RAD test showed a reliable diagnostic response in subjects that displayed high C t values, corresponding to high viral load, while low ability was displayed to identify positive cases with medium‐low C t values, thus presenting low viral load and where confirmatory RT‐PCR was needed. Our finding supports the use of the RAD test in real‐life settings where a high volume of swabs is being processed but with caution when interpreting a positive test result in a low prevalence setting.

Objective:The objective of this review was to determine the diagnostic accuracy of the currently available and upcoming point-of-care rapid antigen tests (RATs) used in primary care settings relative to the viral genetic real-time reverse transcriptase polymerase chain reaction (RT-PCR) test as a reference for diagnosing COVID-19/SARS-CoV-2 in adults.Introduction:Accurate COVID-19 point-of-care diagnostic tests are required for real-time identification of SARS-CoV-2 infection in individuals. Real-time RT-PCR is the accepted gold standard for diagnostic testing, requiring technical expertise and expensive equipment that are unavailable in most primary care locations. RATs are immunoassays that detect the presence of a specific viral protein, which implies a current infection with SARS-CoV-2. RATs are qualitative or semi-quantitative diagnostics that lack thresholds that provide a result within a short time frame, typically within the hour following sample collection. In this systematic review, we synthesized the current evidence regarding the accuracy of RATs for detecting SARS-CoV-2 compared with RT-PCR.Inclusion criteria:Studies that included nonpregnant adults (18 years or older) with suspected SARS-CoV-2 infection, regardless of symptomology or disease severity, were included. The index test was any available SARS-CoV-2 point-of-care RAT. The reference test was any commercially distributed RT-PCR–based test that detects the RNA genome of SARS-CoV-2 and has been validated by an independent third party. Custom or in-house RT-PCR tests were also considered, with appropriate validation documentation. The diagnosis of interest was COVID-19 disease and SARS-CoV-2 infection. This review considered cross-sectional and cohort studies that examined the diagnostic accuracy of COVID-19/SARS-CoV-2 infection where the participants had both index and reference tests performed.Methods:The keywords and index terms contained in relevant articles were used to develop a full search strategy for PubMed and adapted for Embase, Scopus, Qinsight, and the WHO COVID-19 databases. Studies published from November 2019 to July 12, 2022, were included, as SARS-CoV-2 emerged in late 2019 and is the cause of a continuing pandemic. Studies that met the inclusion criteria were critically appraised using QUADAS-2. Using a customized tool, data were extracted from included studies and were verified prior to analysis. The pooled sensitivity, specificity, positive predictive, and negative predictive values were calculated and presented with 95% CIs. When heterogeneity was observed, outlier analysis was conducted, and the results were generated by removing outliers.Results:Meta-analysis was performed on 91 studies of 581 full-text articles retrieved that provided true-positive, true-negative, false-positive, and false-negative values. RATs can identify individuals who have COVID-19 with high reliability (positive predictive value 97.7%; negative predictive value 95.2%) when considering overall performance. However, the lower level of sensitivity (67.1%) suggests that negative test results likely need to be retested through an additional method.Conclusions:Most reported RAT brands had only a few studies comparing their performance with RT-PCR. Overall, a positive RAT result is an excellent predictor of a positive diagnosis of COVID-19. We recommend that Roche’s SARS-CoV-2 Rapid Antigen Test and Abbott’s BinaxNOW tests be used in primary care settings, with the understanding that negative results need to be confirmed through RT-PCR. We recommend adherence to the STARD guidelines when reporting on diagnostic data.Review registration:PROSPERO CRD42020224250

Diagnostic capacity of rapid influenza antigen test: Reappraisal with experience from the 2009 H1N1 pandemic

Introduction: For the diagnosis of Coronavirus Disease 2019 (COVID-19) disease, Real-Time Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) is a laboratory-based technique and is considered a gold standard test, but is time consuming. A Rapid Antigen Test (RAT) is used for screening which is an immunoassay that identifies the presence of a viral antigen causing infection at the point of care. The RAT is quick, inexpensive, easily accessible and doesn’t need lab handling or sample preprocessing. Aim: To measure the sensitivity, specificity, Negative Predictive Value (NPV) and Positive Predictive Value (PPV) of RAT in comparison to RT-PCR. Materials and Methods: This retrospective study was conducted in Department of Community Medicine at Government Medical College (tertiary care centre), Surat, Gujarat, India, using secondary data from 1st July 2020 to 5th Dec 2020. The samples were collected from all the patients of Acute Respiratory Illness (ARI), Severe Acute Respiratory Illness (SARI), Influenza Like Illness (ILI), the suspected COVID-19 cases and all walk in patients for testing or treatment purposes. A total of 264 participants enrolled in the study underwent both the RAT and RT-PCR tests. The sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) were calculated using MS Excel Statistical Package for the Social Sciences (SPSS) version 17.0. Results: Total 264 cases were analysed, amongst which 161 (60.9%) were males and 103 (39.1%) were females and the mean age of the patient was 41.6 years and 36.8 years for males and females, respectively. The overall sensitivity was 52.47%, specificity was 87.11%, PPV was 71.62% and the NPV was 74.73%. While among symptomatic patients sensitivity was 55.55%, specificity was 88.54%, PPV was 76.97% and NPV was 74.35%. Conclusion: Because of the low sensitivity of the RAT, if used alone a high number of false negative cases will be resulted. Hence, it is employed in community and clinical settings as sequential screening in conjunction with RT-PCR, which results in improved net gain and aids in disease transmission control.

Screening of asymptomatic patients upon hospital admission became a key strategy to prevent nosocomial transmission of SARS-CoV-2 during the COVID-19 pandemic, particularly in facilities treating immunocompromised patients. Rapid antigen tests (RATs) were widely used due to their speed, but their reliability in detecting potentially infectious individuals remained debated. In parallel, the role of immunosuppression, especially in solid organ transplant (SOT) recipients, as a risk factor for asymptomatic positivity and prolonged viral shedding raised additional concerns. The aim of the study was to evaluate the diagnostic performance of rapid antigen testing compared to RT-PCR in asymptomatic patients admitted to a high-risk hospital, and the difference in SARS-CoV-2 PCR positivity between asymptomatic patients with and without a history of solid organ transplantation. We retrospectively analysed 17,086 paired RAT and RT-PCR tests collected from 11,858 asymptomatic patients admitted to a tertiary care hospital between October 2020 and October 2022. Viral load was assessed via PCR cycle threshold (Ct) values. The sensitivity and specificity of RATs were calculated using PCR as the reference (Ct < 28). RATs showed a sensitivity of 83.5% and a specificity of 99.3% in detecting patients with high viral loads (Ct < 28). False negatives occurred predominantly in cases with low viral loads (Ct ≥ 28). SARS-CoV-2 PCR positivity was significantly higher in SOT patients (5.4%) than in non-transplant patients (3.2%) (p < 0.001), a difference that was consistent across viral variants. RATs reliably identified the majority of asymptomatic patients with high viral loads who pose a risk of in-hospital transmission. SOT recipients represent a high-risk subgroup for asymptomatic SARS-CoV-2 carriage, underscoring the importance of rigorous admission screening protocols in specialized healthcare settings.

Background and aimRapid antigen detection (RAD) tests on nasopharyngeal specimens have been recently made available for SARS-CoV-2 infections, and early studies suggested their potential utilization as rapid screening and diagnostic testing. The present systematic review and meta-analysis was aimed to assess available evidence and to explore the reliability of antigenic tests in the management of the SARS-CoV-2 pandemic.Materials and MethodsWe reported our meta-analysis according to the PRISMA statement. We searched Pubmed, Embase, and pre-print archive medRxiv.og for eligible studies published up to November 5th, 2020. Raw data included true/false positive and negative tests, and the total number of tests. Sensitivity and specificity data were calculated for every study, and then pooled in a random-effects model. Heterogeneity was assessed using the I2 measure. Reporting bias was assessed by means of funnel plots and regression analysis.ResultsBased on 25 studies, we computed a pooled sensitivity of 72.8% (95%CI 62.4–81.3), a specificity of 99.4% (95%CI 99.0–99.7), with high heterogeneity and risk of reporting bias. More precisely, RAD tests exhibited higher sensitivity on samples with high viral load (i.e. <25 Cycle Threshold; 97.6%; 95%CI 94.1–99.0), compared to those with low viral load (≥25 Cycle Threshold; 43.6%; 95% 27.6-61.1).DiscussionAs the majority of collected reports were either cohort or case-control studies, deprived of preventive power analysis and often oversampling positive tests, overall performances may have been overestimated. Therefore, the massive referral to antigenic tests in place of RT-qPCR is currently questionable, and also their deployment as mass screening test may lead to intolerable share of missing diagnoses. On the other hand, RAD tests may find a significant role in primary care and in front-line settings (e.g. Emergency Departments). (www.actabiomedica.it)

The coronavirus disease 2019 (COVID-19) pandemic is our time's major global health crisis and the greatest health challenge. Reverse transcription-polymerase chain reaction (RT-PCR) test for severe acute respiratory syndrome coronavirus (SARS-CoV-2) is the gold standard technique for diagnosis of symptomatic cases and asymptomatic carriers. By 2020, antigen rapid tests have been approved for use in Covid-19 testing by regulatory bodies all over the world owing to their benefits as they are rapid and cost effective. This work aimed to determine the diagnostic sensitivity and accuracy of the SARS-CoV-2 rapid antigen test in the detection of SARS-CoV-2 infection compared to RT-PCR data. The study included 111 symptomatic COVID-19 patients and 20 control subjects. Of the 111 study patients, 91 patients (81.98%) were positive by RT-PCR and 20 patients negative. The BIOZEK antigen COVID-19 Ag rapid test device was evaluated using sera from the 111 symptomatic COVID-19 patients. Of the 91 RT-PCR positive patients, 81 (90.1%) were positive by the antigen rapid diagnostic test (Ag-RDT). The control subjects were negative by both tests. The overall sensitivity, specificity, PPV, NPV, and accuracy of the Ag-RDT were 91.11%, 100%, 100%, 68.9%, and 91.8%, respectively and these increased as the level of viremia increased. In conclusion, the used Ag-RDT showed high sensitivity and accuracy for detecting of a SARS-CoV-2 infection, especially when the viral load was high. However, the test lacks sensitivity particularly in those with low viral load.

Background: Infection with respiratory syncytial virus (RSV) in neonates is associated with significant morbidity and mortality. Early and accurate detection of RSV infection is important for appropriate isolation and cohorting, appropriate antibiotic usage, antiviral treatment, and public health awareness. However, RSV rapid antigen test performance has not been evaluated for neonates. Methods: A retrospective analysis of rapid RSV antigen testing in neonates (≤30 days) using a laboratory database of the Diagnostic Virology Laboratory at Texas Children's Hospital acquired between 1997 and 2008 was performed. Of 3691 respiratory samples collected consecutively, 784 (21%) were positive for RSV by rapid test and 402 (10.9%) showed growth of RSV in viral culture. Sensitivity, specificity, positive predictive values, and negative predictive values were calculated using viral culture as the reference standard. P values were calculated utilizing Pearson chi-square with SPSS Statistics 17.0. Result: Overall sensitivity was 90.3% and specificity was 88.2%. Sensitivity was lower in nonseason samples (76.5% vs. 90.9% [P = 0.048]), but specificity was higher in nonseason samples (95.6% vs. 87.1% [P ≤ 0.001]). Lower specificity was seen in samples submitted from neonates evaluated in the emergency department compared with inpatient floors, neonatal intensive care unit, and unspecified venues (85.1% vs. 95.6%, 94.3%, 95.5%, respectively P ≤ 0.001). Overall, there was no statistical difference in test performance based on specimen type. However, when RSV was in season, nasal washes were more sensitive than tracheal aspirates (P = 0.017). Conclusions: Rapid RSV antigen testing was sensitive and specific in detecting RSV infections in neonates. Moderate differences in test performance occurred in and out of RSV season, by sample type, and by the location within the hospital from where the sample was obtained.

The reverse transcriptase polymerase chain reaction (RT-PCR) continues to be the reference diagnostic method for the confirmation of COVID-19 cases; however, rapid antigen detection tests (RADT) have recently been developed. The purpose of the study is to assess the performance of rapid antigen-based COVID-19 testing in the context of hospital outbreaks. This was an observational, cross-sectional study. The study period was from October 2020 to January 2021. The “Panbio COVID-19 AG” RADT (Abbott) was performed and TaqPath COVID-19 test RT-PCR. The samples were obtained from hospitalised patients in suspected outbreak situations at the Ramón y Cajal Hospital. A hospital outbreak was defined as the presence of 3 or more epidemiologically linked cases. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the RADT were calculated using RT-PCR as a reference. A total of 17 hospital outbreaks were detected in 11 hospital units during the study period, in which 34 RT-PCR and RADT screenings were performed. We obtained 541 samples, which were analysed with RT-PCR and a further 541 analysed with RADT. Six RADT tests gave conflicting results with the RT-PCR, 5 of them with a negative RADT and positive RT-PCR and one with positive RADT and a negative RT-PCR. The sensitivity of the RADT was 83.3% (65.3–94.4%) and the specificity was 99.8% (98.9–100%). The PPV was 96.2% (80.4–99.9%) and the NPV was 99% (97.7–99.7%). The RADT shows good diagnostic performance in patients on non-COVID-19 hospital wards, in the context of an outbreak.