Panbio™ rapid antigen test for SARS-CoV-2 has acceptable accuracy in symptomatic patients in primary health care

The sensitivity and specificity of Abbott Panbio™ COVID 19 Ag Rapid test in the context of four SARS-CoV-2 variants

Rapid antigen tests for the detection of SARS-CoV-2 are commonly used for the diagnosis of Covid-19. Previously published data showed a wide range of sensitivity and specificity of RATs, but these studies were performed on relatively small numbers of samples and using only limited numbers of virus variants. The aim of the study was to evaluate the main parameters of a commonly used RAT for 4 different virus variants in comparison with PCR.

Material and methods

A set of 2874 samples obtained from Covid-19 patients were examined both by PCR and RAT. Two commercial PCR kits (Generi Biotech, Diana Biotechnologies) and one RAT - Abbott Panbio™ COVID 19 Ag Rapid - were compared for their sensitivity and specificity in samples positive for one of the four different SARS-CoV-2 variants - B.1.258 (n = 496), Alpha (n = 645), Delta/Delta+ (n = 687), and Omicron (n = 1046).

Results

The sensitivity of Panbio™ COVID19 Ag Rapid test varied from 80.0 % in Omicron to 88.92 % in Alpha variants. The specificities of the RAT for all variants reached above 93 %. Statistically significant differences were found between the results from RAT assay in select virus variants. In addition, significantly higher sensitivity (p < 0.05) was detected in samples with higher viral loads than in those with lower.

Conclusion

Despite the different sensitivity and specificity of Panbio™ COVID19 Ag Rapid test (Abbott ®) for different SARS-CoV-2 variants, this test sensitivity was proven to be always above the 80 % suggested by WHO, which makes it suitable for common use, regardless of the virus variability.

Diagnostic evaluation of Panbio™ antigen rapid diagnostic test for SARS-CoV-2: A systematic review and meta-analysis

INTRODUCTION

The reverse transcriptase polymerase chain reaction (RT-PCR) is the reference diagnostic method for the confirmation of SARS-CoV-2 infected cases. However, various antigen rapid diagnostic tests (Ag-RDTs) have been developed. The purpose of this meta-analysis study was to assess the diagnostic performance of Panbio™ Ag-RDT (Abbott Point of Care) in identifying the SARS-CoV-2 virus.

METHODS

We systematically searched eight databases from March 2020 until March 2023 to look for potentially eligible articles. Diagnostic meta-analysis of Panbio™ Ag-RDT used diverse evaluation indicators, including sensitivity, specificity, Diagnostic Odds Ratio (DOR), and the area under the curve (AUC) value.

RESULTS

Of the 794 articles identified, 49 studies met the inclusion criteria. The pooled estimates of Panbio™ Ag-RDT for the diagnosis of SARS-CoV-2 were 0,65 (95% CI: 0,64-0,66), 0,99 (95% CI: 0,99-1,00), 578,03 (95% CI: 333,37-1002,26) for sensitivity, specificity, and DOR, respectively. Moreover, the summary receiver operating characteristic (SROC) curve revealed an AUC value of 0,942 (95% CI: 0,941-0,943), suggesting an outstanding diagnostic accuracy. Subgroup and meta-regression analyses showed that continent, study period, age, study population and cycle threshold (Ct) values constituted a source of heterogeneity. Furthermore, we demonstrated proof of publication bias for DOR values analyzed using Deek's test (p = 0,001) and funnel plot.

CONCLUSION

Panbio™ Ag-RDT presented an outstanding diagnostic accuracy in the detection of the SARS-CoV-2 virus in both adults and children with or without symptoms.

Diagnostic accuracy of Panbio™ rapid antigen test for SARS-CoV-2 in paediatric population

BACKGROUND

Rapid antigen-detection tests (Ag-RDTs) are used to diagnose SARS-CoV-2 infection. Real-world studies of Ag-RDTs are necessary to evaluate their diagnostic yield in paediatric patients. Our aim was to evaluate the accuracy of the Panbio™ Rapid Antigen Test for SARS-CoV-2 in the setting of a primary health care centre (PHC), with use of the Reverse Transcription-Polymerase Chain Reaction (RT-PCR) as gold standard.

METHODS

This prospective diagnostic study was conducted at PHCs in Mallorca, Spain. Patients were ≤ 18 years-old that attended sites for RT-PCR testing due to symptoms suggestive of infection (fever, headache, nasal congestion and dry cough, among others) or epidemiological exposure (close contacts). Two samples were collected: a nasal mid-turbinate sample for Ag-RDTs and a nasopharyngeal swab for RT-PCR testing. The sensitivity, specificity, and predictive values of the AgRDT were calculated using the RT-PCR results as the reference.

RESULTS

We examined 1142 participants from 0 to 18 years (47.5% female, mean age 8.9 ± 4.8 years, median 9.0 [5.0-13.0]). There were 84 positive RT-PCR results (pre-test probability of 7.3%) and 52 positive Ag-RDT results. The sensitivity of the Ag-RDT was 59.5% (95% Confidence Interval (CI): 48.2-69.9%), the specificity was 99.8% (95%CI: 99.2-99.9%), the positive predictive value was 96.1% (95%CI: 85.6-99.4%), and the negative predictive value was 96.8% (95%CI: 95.6-97.7%). The sensitivity for individuals referred by a general practitioner (GP) or paediatrician due to symptoms was 71.4% (95%CI: 51.5-86.0%) and for asymptomatic individuals was 50.0% (95%CI: 9.1-90.8%). The specificity was greater than 98.9% overall and in all subgroups. The sensitivity was 73.0% (95%CI: 52.0-87.5%) for referred patients due to symptoms and who were tested within 5 days since symptom onset. No significant statistical differences between any groups were found. There were 34 false-negative Ag-RDT results (40.5%) and 2 false-positive Ag-RDT results (0.2%).

CONCLUSION

The sensitivity of the Panbio™ Test in paediatric individuals is below the minimum of 80% recommended by the World Health Organization for Ag-RDTs. This test had better accuracy in individuals referred by a GP or paediatrician due to symptoms, rather than those who were asymptomatic or referred due to epidemiological exposure. The RT-PCR test using a nasopharyngeal swab is accurate, but a less invasive alternative that has better sensitivity than the Panbio™ Test is needed for paediatric populations.

COVID-19 in Morocco's region: Observational study of prevalence in symptomatic adults using the PANBIOS® rapid antigen test September 2021

Background

Rapid antigen tests have emerged to deal with the COVID-19 pandemic. Rapid diagnosis of SARS-CoV-2 infection is essential to reduce the spread of the disease. The aim of this study was to estimate the prevalence of COVID-19 infection and test the sensitivity and specificity in Temara-Skhirat in symptomatic adults through PANBIOS® test.

Methods

A prospective observational study was conducted in mid-September 2021. Two investigators conducted data collection from symptomatic adult patients. The diagnostic performance of the PANBIOS®, and the PCR was assessed to calculate sensitivity and the specificity.

Results

Among 206 symptomatic participants, the mean age was 38 ± 12 years, and the majority were women (59%). In our population, 80% had benefited from the anti-COVID vaccine. The median duration of symptoms was 4 days; the most common symptoms were fatigue (62%), headache (52%), fever (48%), cough (34%), loss of smell (25%), loss of taste (24%), and sore throat (22%). Results revealed 23% of cases tested positive with PANBIOS® test versus 30% with the PCR test. The calculated medical decision between PCR versus PANBIOS® test showed high specificity of 95.7% and a sensitivity of 69.4%. There was concordance between the PANBIOS® test and the PCR.

Conclusion

The prevalence tested remain high, and the sensitivity and specificity of the PANBIOS® versus PCR test are similar to other literatures and close to value described in WHO recommendations. PANBIOS® is a useful test for controlling the spread of COVID-19 allowing identification of active infection.

CoVSense: Ultrasensitive Nucleocapsid Antigen Immunosensor for Rapid Clinical Detection of Wildtype and Variant SARS-CoV-2

The widespread accessibility of commercial/clinically-viable electrochemical diagnostic systems for rapid quantification of viral proteins demands translational/preclinical investigations. Here, Covid-Sense (CoVSense) antigen testing platform; an all-in-one electrochemical nano-immunosensor for sample-to-result, self-validated, and accurate quantification of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid (N)-proteins in clinical examinations is developed. The platform's sensing strips benefit from a highly-sensitive, nanostructured surface, created through the incorporation of carboxyl-functionalized graphene nanosheets, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) conductive polymers, enhancing the overall conductivity of the system. The nanoengineered surface chemistry allows for compatible direct assembly of bioreceptor molecules. CoVSense offers an inexpensive (<$2 kit) and fast/digital response (<10 min), measured using a customized hand-held reader (<$25), enabling data-driven outbreak management. The sensor shows 95% clinical sensitivity and 100% specificity (Ct<25), and overall sensitivity of 91% for combined symptomatic/asymptomatic cohort with wildtype SARS-CoV-2 or B.1.1.7 variant (N = 105, nasal/throat samples). The sensor correlates the N-protein levels to viral load, detecting high Ct values of ≈35, with no sample preparation steps, while outperforming the commercial rapid antigen tests. The current translational technology fills the gap in the workflow of rapid, point-of-care, and accurate diagnosis of COVID-19.

The Infectious Diseases Society of America Guidelines on the Diagnosis of COVID-19: Antigen Testing

BACKGROUND

Immunoassays designed to detect SARS-CoV-2 protein antigens (Ag) are commonly used to diagnose COVID-19. The most widely used tests are lateral flow assays that generate results in approximately 15 minutes for diagnosis at the point-of-care. Higher throughput, laboratory-based SARS-CoV-2 Ag assays have also been developed. The number of commercially available SARS-CoV-2 Ag detection tests has increased rapidly, as has the COVID-19 diagnostic literature. The Infectious Diseases Society of America (IDSA) convened an expert panel to perform a systematic review of the literature and develop best practice guidance related to SARS-CoV-2 Ag testing. This guideline is an update to the third in a series of frequently updated COVID-19 diagnostic guidelines developed by the IDSA.

OBJECTIVE

The IDSA's goal was to develop evidence-based recommendations or suggestions that assist clinicians, clinical laboratories, patients, public health authorities, administrators and policymakers in decisions related to the optimal use of SARS-CoV-2 Ag tests in both medical and non-medical settings.

METHODS

A multidisciplinary panel of infectious diseases clinicians, clinical microbiologists and experts in systematic literature review identified and prioritized clinical questions related to the use of SARS-CoV-2 Ag tests. A review of relevant, peer-reviewed published literature was conducted through April 1, 2022. Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology was used to assess the certainty of evidence and make testing recommendations.

RESULTS

The panel made ten diagnostic recommendations. These recommendations address Ag testing in symptomatic and asymptomatic individuals and assess single versus repeat testing strategies.

CONCLUSIONS

U.S. Food and Drug Administration (FDA) SARS-CoV-2 Ag tests with Emergency Use Authorization (EUA) have high specificity and low to moderate sensitivity compared to nucleic acid amplification testing (NAAT). Ag test sensitivity is dependent on the presence or absence of symptoms, and in symptomatic patients, on timing of testing after symptom onset. In contrast, Ag tests have high specificity, and, in most cases, positive Ag results can be acted upon without confirmation. Results of point-of-care testing are comparable to those of laboratory-based testing, and observed or unobserved self-collection of specimens for testing yields similar results. Modeling suggests that repeat Ag testing increases sensitivity compared to testing once, but no empirical data were available to inform this question. Based on these observations, rapid RT-PCR or laboratory-based NAAT remains the testing method of choice for diagnosing SARS-CoV-2 infection. However, when timely molecular testing is not readily available or is logistically infeasible, Ag testing helps identify individuals with SARS-CoV-2 infection. Data were insufficient to make a recommendation about the utility of Ag testing to guide release of patients with COVID-19 from isolation. The overall quality of available evidence supporting use of Ag testing was graded as very low to moderate.

Diagnostic accuracy of the Panbio COVID-19 antigen rapid test device for SARS-CoV-2 detection in Kenya, 2021: A field evaluation

BACKGROUND

Accurate and timely diagnosis is essential in limiting the spread of SARS-CoV-2 infection. The reference standard, rRT-PCR, requires specialized laboratories, costly reagents, and a long turnaround time. Antigen RDTs provide a feasible alternative to rRT-PCR since they are quick, relatively inexpensive, and do not require a laboratory. The WHO requires that Ag RDTs have a sensitivity ≥80% and specificity ≥97%.

METHODS

This evaluation was conducted at 11 health facilities in Kenya between March and July 2021. We enrolled persons of any age with respiratory symptoms and asymptomatic contacts of confirmed COVID-19 cases. We collected demographic and clinical information and two nasopharyngeal specimens from each participant for Ag RDT testing and rRT-PCR. We calculated the diagnostic performance of the Panbio™ Ag RDT against the US Centers for Disease Control and Prevention's (CDC) rRT-PCR test.

RESULTS

We evaluated the Ag RDT in 2,245 individuals where 551 (24.5%, 95% CI: 22.8-26.3%) tested positive by rRT-PCR. Overall sensitivity of the Ag RDT was 46.6% (95% CI: 42.4-50.9%), specificity 98.5% (95% CI: 97.8-99.0%), PPV 90.8% (95% CI: 86.8-93.9%) and NPV 85.0% (95% CI: 83.4-86.6%). Among symptomatic individuals, sensitivity was 60.6% (95% CI: 54.3-66.7%) and specificity was 98.1% (95% CI: 96.7-99.0%). Among asymptomatic individuals, sensitivity was 34.7% (95% CI 29.3-40.4%) and specificity was 98.7% (95% CI: 97.8-99.3%). In persons with onset of symptoms <5 days (594/876, 67.8%), sensitivity was 67.1% (95% CI: 59.2-74.3%), and 53.3% (95% CI: 40.0-66.3%) among those with onset of symptoms >7 days (157/876, 17.9%). The highest sensitivity was 87.0% (95% CI: 80.9-91.8%) in symptomatic individuals with cycle threshold (Ct) values ≤30.

CONCLUSION

The overall sensitivity and NPV of the Panbio™ Ag RDT were much lower than expected. The specificity of the Ag RDT was high and satisfactory; therefore, a positive result may not require confirmation by rRT-PCR. The kit may be useful as a rapid screening tool only for symptomatic patients in high-risk settings with limited access to rRT-PCR. A negative result should be interpreted based on clinical and epidemiological information and may require retesting by rRT-PCR.

Evaluation of the diagnostic performance of PanbioTM Abbott SARS-CoV-2 rapid antigen test for the detection of COVID-19 from suspects attending ALERT center

BACKGROUND

The emergence and rapid spread of coronavirus disease 2019 (COVID-19), a potentially lethal disease caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), is causing public health issues around the world. In resource-constrained nations, rapid Abbott SARS-CoV-2 antigen test kits are critical for addressing diagnostic gaps in health institutions and community screening. However, there is no evidence or proof of diagnostic performance in Ethiopia. The aim of this study was to compare the performance of PanbioTM Abbott SARS-CoV-2antigen rapid test kit to the gold standard, RT-PCR, in COVID-19 patients with clinical symptoms suggestive of COVID-19.

METHOD

A prospective, cross-sectional study was conducted between November 2021 and April 2022, on 120 suspected patients recruited from outpatient, emergency, and intensive care units in one of the tertiary hospitals in Ethiopia. Nasopharyngeal swabs were collected from suspected cases and were tested using the Abbott SARS-CoV-2 kit, a rapid diagnostic test (RDT) and compared to the reference standard RT-PCR.

RESULT

The sensitivity and specificity of the RDT were 74.2% and 100%, respectively. A total of 62 samples (51.6%) were RT-PCR positive. Of these, 46 were Ag-RDT positive. Sensitivity among symptomatic patients was 79.4% (95% CI 68.3-90). The Abbot RDT and RT-PCR had a Kappa value of agreement of 0.735 (p < 0.001). These values were acceptable when compared to the WHO's suggested thresholds.

CONCLUSION

The finding from this study support the use of the Abbot RDT as a diagnostic tool in COVID-19 suspects, mainly in those with higher viral loads.

Lateral Flow Immunoassays for SARS-CoV-2

The continued circulation of SARS-CoV-2 virus in different parts of the world opens up the possibility for more virulent variants to evolve even as the coronavirus disease 2019 transitions from pandemic to endemic. Highly transmissible and virulent variants may seed new disruptive epidemic waves that can easily put the healthcare system under tremendous pressure. Despite various nucleic acid-based diagnostic tests that are now commercially available, the wide applications of these tests are largely hampered by specialized equipment requirements that may not be readily available, accessible and affordable in less developed countries or in low resource settings. Hence, the availability of lateral flow immunoassays (LFIs), which can serve as a diagnostic tool by detecting SARS-CoV-2 antigen or as a serological tool by measuring host immune response, is highly appealing. LFI is rapid, low cost, equipment-free, scalable for mass production and ideal for point-of-care settings. In this review, we first summarize the principle and assay format of these LFIs with emphasis on those that were granted emergency use authorization by the US Food and Drug Administration followed by discussion on the specimen type, marker selection and assay performance. We conclude with an overview of challenges and future perspective of LFI applications.

Decreased Sensitivity of Rapid Antigen Test Is Associated with a Lower Viral Load of Omicron than Delta SARS-CoV-2 Variant

Large-scale screening for SARS-CoV-2 infection is an important tool for epidemic prevention and control. The appearance of new variants associated with specific mutations can call into question the effectiveness of rapid diagnostic tests (RDTs) deployed massively at national and international levels. We compared the clinical and virological characteristics of individuals infected by Delta or Omicron variants to assess which factors were associated with a reduced performance of RDT. A commercially available RDT as well as the evaluation of the viral load (VL) and the detection of replicate intermediates (RIs) were carried out retrospectively on positive SARS-CoV-2 nasopharyngeal specimens from health care workers of the Pitié-Salpêtrière Hospital infected by the Delta or Omicron variant between July 2021 and January 2022. Of the 205 samples analyzed (104 from individuals infected with Delta and 101 with Omicron), 176 were analyzed by RDT and 200 by RT-PCR for VL and RIs. The sensitivity of the TDR for Omicron was significantly lower than that observed for Delta (53.8% versus 74.7%, respectively, P < 0.01). Moreover, the Delta VL was significantly higher than that measured for Omicron (median Ct 21.2 versus 24.1, respectively, P < 0.01) and associated with the positivity of the RDT in multivariate analysis. We demonstrate a lower RDT sensitivity associated with a lower VL at the time of diagnosis on Omicron-infected individuals in comparison to those infected with the Delta variant. This RDT lower sensitivity should be taken into account in the large-scale screening strategy and in particular in case of strong suspicion of infection where testing should be repeated. IMPORTANCE Previous reports have shown a variability in the diagnostic performance of RDTs. In the era of SARS-CoV-2 variants and the use of RDT, mutation associated with these variants could affect the test performance. We evaluate the sensitivity of the RDT Panbio COVID-19 Ag (Abbott) with two variants of concern (VOC), the Delta and Omicron variants. In order to investigate whether clinical characteristics or virological characteristics can affect this sensitivity, we collected clinical information and performed a specific RT-PCR that detected the RIs as a marker of the viral replication and viral cycle stage. Our results showed that Omicron was less detected than the Delta variant. A lower viral load of Omicron variant in comparison to Delta variant explained this decreased sensitivity, even if they are at the same stage of the disease and the viral cycle and should be taken into account with the use of RDT as diagnostic tool.

Daily, self-test rapid antigen test to assess SARS-CoV-2 viability in de-isolation of patients with COVID-19

Background

Isolation of COVID-19 patients is a crucial infection control measure to prevent further SARS-CoV-2 transmission, but determining an appropriate timing to end the COVID-19 isolation is a challenging. We evaluated the performance of the self-test rapid antigen test (RAT) as a potential proxy to terminate the isolation of COVID-19 patients.

Materials and methods

Symptomatic COVID-19 patients were enrolled who were admitted to a regional community treatment center (CTC) in Seoul (South Korea). Self-test RAT and the collection of saliva samples were performed by the patients, on a daily basis, until patient discharge. Cell culture and subgenomic RNA detection were performed on saliva samples.

Results

A total of 138 pairs of saliva samples and corresponding RAT results were collected from 34 COVID-19 patients. Positivity of RAT and cell culture was 27% (37/138) and 12% (16/138), respectively. Of the 16 culture-positive saliva samples, seven (43.8%) corresponding RAT results were positive. Using cell culture as the reference standard, the overall percent agreement, percent positive agreement, and percent negative agreement of RAT were 71% (95% CI, 63–78), 26% (95% CI, 12–42), and 82% (95% CI, 76–87), respectively. The sensitivity, specificity, positive predictive value, and negative predictive value of the RAT for predicting culture results were 44% (95% CI, 20–70), 75% (95% CI, 66–82), 18% (95% CI, 8–34), and 91% (95% CI, 84–96), respectively.

Conclusion

About half of the patients who were SARS-CoV-2 positive based upon cell culture results gave negative RAT results. However, the remaining positive culture cases were detected by RAT, and RAT showed relatively high negative predictive value for viable viral shedding.

Evaluating diagnostic accuracies of Panbio™ test and RT-PCR for the detection of SARS-CoV-2 in Addis Ababa, Ethiopia using Bayesian Latent-Class Models (BLCM)

BACKGROUND

Rapid diagnostics are vital for curving the transmission and control of the COVID-19 pandemic. Although many commercially available antigen-based rapid diagnostic tests (Ag-RDTs) for the detection of SARS-CoV-2 are recommended by the WHO, their diagnostic performance has not yet been assessed in Ethiopia. So far, the vast majority of studies assessing diagnostic accuracies of rapid antigen tests considered RT-PCR as a reference standard, which inevitably leads to bias when RT-PCR is not 100% sensitive and specific. Thus, this study aimed to evaluate the diagnostic performance of Panbio™ jointly with the RT-PCR for the detection of SARS-CoV-2.

METHODS

A prospective cross-sectional study was done from July to September 2021 in Addis Ababa, Ethiopia, during the third wave of the pandemic involving two health centers and two hospitals. Diagnostic sensitivity and specificity of Panbio™ and RT-PCR were obtained using Bayesian Latent-Class Models (BLCM).

RESULTS

438 COVID-19 presumptive clients were enrolled, 239 (54.6%) were females, of whom 196 (44.7%) had a positive RT-PCR and 158 (36.1%) were Panbio™ positive. The Panbio™ and RT-PCR had a sensitivity (95% CrI) of 99.6 (98.4-100) %, 89.3 (83.2-97.6) % and specificity (95% CrI) of 93.4 (82.3-100) %, and 99.1 (97.5-100) %, respectively. Most of the study participants, 318 (72.6%) exhibited COVID-19 symptoms; the most reported was cough 191 (43.6%).

CONCLUSION

As expected the RT-PCR performed very well with a near-perfect specificity and a high, but not perfect sensitivity. The diagnostic performance of Panbio™ is coherent with the WHO established criteria of having a sensitivity ≥80% for Ag-RDTs. Both tests displayed high diagnostic accuracies in patients with and without symptoms. Hence, we recommend the use of the Panbio™ for both symptomatic and asymptomatic individuals in clinical settings for screening purposes.

Accuracy of point-of-care Panbio™ SARS-CoV-2 antigen-detection test in a socioeconomically vulnerable population in Brazil

Background

Development and validation of point-of-care (POC) diagnostic tests with high accuracy is critical for underrepresented populations, allowing for wider access to diagnosis. Here, we evaluate the performance of the Panbio™ antigen-rapid test device (Ag-RTD) for SARS-CoV-2, our index test, having RT-qPCR as the reference standard.

Methods

This phase III validation study was conducted concomitantly with a primary health care center routine tending to a low-income Brazilian population. Eligibility criteria were residing at Cidade Estrutural and presenting flu-like/respiratory symptoms for 3-10 days.

Results

Among the 505 participants, 45.15% (228/505) tested positive for RT-qPCR and 54.85% (277/505) for the Ag-RTD. Overall sensitivity was 76.32% (CI95% 70.39-81.37) and specificity was 98.92% (96.02-99.82).

Conclusions

Our results show that the Panbio™ Ag-RTD does not meet the minimum performance requirements established by the World Health Organization (≥ 80% sensitivity and ≥ 97% specificity compared to a reference test in suspected COVID-19 cases). Thus, we do not recommend the implementation of Panbio™Ag-RTD as a single diagnostic tool in underrepresented and disadvantaged populations. Finally, we discuss a possible setting for the use of Panbio™Ag-RTD under combined sensitivity.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) antigen detection in the Emergency Department: data from a pediatric cohort during the fourth COVID-19 wave in Italy

BACKGROUND

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic has been challenging health care systems and made it necessary to use rapid and cost-effective testing methods, particularly in Emergency Department (ED) settings. Rapid Antigen Diagnostic Tests (RADTs) are a valid alternative to the gold standard RT-PCR, even in pediatric populations. This retrospective observational study has been conducted on a pediatric cohort afferent to the ED of the San Giovanni di Dio and Ruggi d'Aragona University Hospital in Salerno, tested at Point of Care with RADT Panbio® (Abbott), from September 1^st, 2021 to February 28^th, 2022, analyzing the positivity rate and clinical features of the cohort, also in reference to the rise of positive cases observed in the aforementioned period, and to the introduction in Italy of SARS-CoV-2 vaccination for children and teens on December 16^th, 2021.

METHODS

Data regarding access to the pediatric ED were extracted from the hospital's electronic database system. Parallel to this, we conducted a narrative literature search using PubMed database focusing on the use of RADT in pediatric ED and compared our data with the national pandemic trend.

RESULTS

During the observation period, 1890 patients were tested for the presence of SARS-CoV-2 with RADT and the 2.7% of children resulted positive, with a peak in January 2022. The main symptoms in positive patients were: fever (n = 34; 66.7%), cough (n = 11; 21.5%), headache (n = 4; 7.8%), chest pain (n = 2; 3.9%) and abdominal pain (n = 1; 2%). Patients were divided into three different age groups (A, B, C) basing on the different access timing to vaccination; no statistically significant difference was detected in the distribution of positivity in these three groups (p > 0.05). Number of positive children in group A was greater in the post-vaccine group. Our data are concordant with the national trend of the pandemic showing a fourth wave peak in January 2022.

CONCLUSION

The use of RADT as a first point-of-care screening may be helpful, time-saving and cost-sparing. Our study shows that, during the observation period, most children admitted to the ED for fever, actually tested positive for SARS-CoV-2 with a statistically greater difference than negative children. Instead, number of patients admitted for cough was statistically higher among negative than positive ones, probably due to the circulation of other respiratory viruses in children.

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.

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

BACKGROUND

Accurate rapid diagnostic tests for SARS-CoV-2 infection would be a useful tool to help manage the COVID-19 pandemic. Testing strategies that use rapid antigen tests to detect current infection have the potential to increase access to testing, speed detection of infection, and inform clinical and public health management decisions to reduce transmission. This is the second update of this review, which was first published in 2020.

OBJECTIVES

To assess the diagnostic accuracy of rapid, point-of-care antigen tests for diagnosis of SARS-CoV-2 infection. We consider accuracy separately in symptomatic and asymptomatic population groups. Sources of heterogeneity investigated included setting and indication for testing, assay format, sample site, viral load, age, timing of test, and study design.

SEARCH METHODS

We searched the COVID-19 Open Access Project living evidence database from the University of Bern (which includes daily updates from PubMed and Embase and preprints from medRxiv and bioRxiv) on 08 March 2021. We included independent evaluations from national reference laboratories, FIND and the Diagnostics Global Health website. We did not apply language restrictions.

SELECTION CRITERIA

We included studies of people with either suspected SARS-CoV-2 infection, known SARS-CoV-2 infection or known absence of infection, or those who were being screened for infection. We included test accuracy studies of any design that evaluated commercially produced, rapid antigen tests. We included evaluations of single applications of a test (one test result reported per person) and evaluations of serial testing (repeated antigen testing over time). Reference standards for presence or absence of infection were any laboratory-based molecular test (primarily reverse transcription polymerase chain reaction (RT-PCR)) or pre-pandemic respiratory sample.

DATA COLLECTION AND ANALYSIS

We used standard screening procedures with three people. Two people independently carried out quality assessment (using the QUADAS-2 tool) and extracted study results. Other study characteristics were extracted by one review author and checked by a second. We present sensitivity and specificity with 95% confidence intervals (CIs) for each test, and pooled data using the bivariate model. We investigated heterogeneity by including indicator variables in the random-effects logistic regression models. We tabulated results by test manufacturer and compliance with manufacturer instructions for use and according to symptom status.

MAIN RESULTS

We included 155 study cohorts (described in 166 study reports, with 24 as preprints). The main results relate to 152 evaluations of single test applications including 100,462 unique samples (16,822 with confirmed SARS-CoV-2). Studies were mainly conducted in Europe (101/152, 66%), and evaluated 49 different commercial antigen assays. Only 23 studies compared two or more brands of test. Risk of bias was high because of participant selection (40, 26%); interpretation of the index test (6, 4%); weaknesses in the reference standard for absence of infection (119, 78%); and participant flow and timing 41 (27%). Characteristics of participants (45, 30%) and index test delivery (47, 31%) differed from the way in which and in whom the test was intended to be used. Nearly all studies (91%) used a single RT-PCR result to define presence or absence of infection. The 152 studies of single test applications reported 228 evaluations of antigen tests. Estimates of sensitivity varied considerably between studies, with consistently high specificities. Average sensitivity was higher in symptomatic (73.0%, 95% CI 69.3% to 76.4%; 109 evaluations; 50,574 samples, 11,662 cases) compared to asymptomatic participants (54.7%, 95% CI 47.7% to 61.6%; 50 evaluations; 40,956 samples, 2641 cases). Average sensitivity was higher in the first week after symptom onset (80.9%, 95% CI 76.9% to 84.4%; 30 evaluations, 2408 cases) than in the second week of symptoms (53.8%, 95% CI 48.0% to 59.6%; 40 evaluations, 1119 cases). For those who were asymptomatic at the time of testing, sensitivity was higher when an epidemiological exposure to SARS-CoV-2 was suspected (64.3%, 95% CI 54.6% to 73.0%; 16 evaluations; 7677 samples, 703 cases) compared to where COVID-19 testing was reported to be widely available to anyone on presentation for testing (49.6%, 95% CI 42.1% to 57.1%; 26 evaluations; 31,904 samples, 1758 cases). Average specificity was similarly high for symptomatic (99.1%) or asymptomatic (99.7%) participants. We observed a steady decline in summary sensitivities as measures of sample viral load decreased. Sensitivity varied between brands. When tests were used according to manufacturer instructions, average sensitivities by brand ranged from 34.3% to 91.3% in symptomatic participants (20 assays with eligible data) and from 28.6% to 77.8% for asymptomatic participants (12 assays). For symptomatic participants, summary sensitivities for seven assays were 80% or more (meeting acceptable criteria set by the World Health Organization (WHO)). The WHO acceptable performance criterion of 97% specificity was met by 17 of 20 assays when tests were used according to manufacturer instructions, 12 of which demonstrated specificities above 99%. For asymptomatic participants the sensitivities of only two assays approached but did not meet WHO acceptable performance standards in one study each; specificities for asymptomatic participants were in a similar range to those observed for symptomatic people. At 5% prevalence using summary data in symptomatic people during the first week after symptom onset, the positive predictive value (PPV) of 89% means that 1 in 10 positive results will be a false positive, and around 1 in 5 cases will be missed. At 0.5% prevalence using summary data for asymptomatic people, where testing was widely available and where epidemiological exposure to COVID-19 was suspected, resulting PPVs would be 38% to 52%, meaning that between 2 in 5 and 1 in 2 positive results will be false positives, and between 1 in 2 and 1 in 3 cases will be missed.

AUTHORS' CONCLUSIONS

Antigen tests vary in sensitivity. In people with signs and symptoms of COVID-19, sensitivities are highest in the first week of illness when viral loads are higher. Assays that meet appropriate performance standards, such as those set by WHO, could replace laboratory-based RT-PCR when immediate decisions about patient care must be made, or where RT-PCR cannot be delivered in a timely manner. However, they are more suitable for use as triage to RT-PCR testing. The variable sensitivity of antigen tests means that people who test negative may still be infected. Many commercially available rapid antigen tests have not been evaluated in independent validation studies. Evidence for testing in asymptomatic cohorts has increased, however sensitivity is lower and there is a paucity of evidence for testing in different settings. Questions remain about the use of antigen test-based repeat testing strategies. Further research is needed to evaluate the effectiveness of screening programmes at reducing transmission of infection, whether mass screening or targeted approaches including schools, healthcare setting and traveller screening.

Performance of Antigen Detection Tests for SARS-CoV-2: A Systematic Review and Meta-Analysis

Coronavirus disease 2019 (COVID-19) initiated global health care challenges such as the necessity for new diagnostic tests. Diagnosis by real-time PCR remains the gold-standard method, yet economical and technical issues prohibit its use in points of care (POC) or for repetitive tests in populations. A lot of effort has been exerted in developing, using, and validating antigen-based tests (ATs). Since individual studies focus on few methodological aspects of ATs, a comparison of different tests is needed. Herein, we perform a systematic review and meta-analysis of data from articles in PubMed, medRxiv and bioRxiv. The bivariate method for meta-analysis of diagnostic tests pooling sensitivities and specificities was used. Most of the AT types for SARS-CoV-2 were lateral flow immunoassays (LFIA), fluorescence immunoassays (FIA), and chemiluminescence enzyme immunoassays (CLEIA). We identified 235 articles containing data from 220,049 individuals. All ATs using nasopharyngeal samples show better performance than those with throat saliva (72% compared to 40%). Moreover, the rapid methods LFIA and FIA show about 10% lower sensitivity compared to the laboratory-based CLEIA method (72% compared to 82%). In addition, rapid ATs show higher sensitivity in symptomatic patients compared to asymptomatic patients, suggesting that viral load is a crucial parameter for ATs performed in POCs. Finally, all methods perform with very high specificity, reaching around 99%. LFIA tests, though with moderate sensitivity, appear as the most attractive method for use in POCs and for performing seroprevalence studies.

Molecular and antigen tests, and sample types for diagnosis of COVID-19: a review

Laboratory tests seeking to improve detection of COVID-19 have been widely developed by laboratories and commercial companies. This review provides an overview of molecular and antigen tests, presents the sensitivity and specificity for 329 assays that have received US FDA Emergency Use Authorization and evaluates six sample collection methods – nasal, nasopharyngeal, oropharyngeal swabs, saliva, blood and stool. Molecular testing is preferred for diagnosis of COVID-19, but negative results do not always rule out the presence of infection, especially when clinical suspicion is high. Sensitivity and specificity ranged from 88.1 to 100% and 88 to 100%, respectively. Antigen tests may be more easy to use and rapid. However, they have reported a wide range of detection sensitivities from 16.7 to 85%, which may potentially yield many false-negative results.

Different performance of three point-of-care SARS-CoV-2 antigen detection devices in symptomatic patients and close asymptomatic contacts: a real-life study

OBJECTIVES

PCR on nasopharyngeal exudates, the cornerstone of the detection of SARS-CoV-2, is time-consuming and commonly unavailable at primary health care centres. Detection of viral nucleocapsid antigens using lateral flow point-of-care tests is helpful for the early triage of patients who attend health care facilities.

METHODS

This was a prospective study carried out in clinically suspected cases and close asymptomatic contacts who attended a primary care centre (Madrid, Spain) for SARS-CoV-2 detection. Patients were divided into three 300-patient cohorts (n = 200 symptomatic cases and n = 100 close asymptomatic contacts per cohort). Three antigen detection tests (SGTI-Flex COVID-19 Ag, Panbio COVID-19 Ag Rapid Test Device, and GSD NovaGen SARS-CoV-2 Ag Rapid Test) were used and compared. Paired nasopharyngeal exudates were obtained, one swab for PCR and the other for antigen detection. Each antigen detection test was evaluated on one cohort.

RESULTS

All tests showed invariably 100% specificity. Sensitivity was 68.9% (95% CI: 55.7-80; SGTI-Flex), 71.1% (95% CI: 55.6-83.6; Panbio), and 84.6% (95% CI: 72-93.1; NovaGen) in clinically suspected patients and 84.6% (95% CI: 54.5-98.1), 33.3% (95% CI: 11.8-61.6), and 55.6% (95% CI: 30.7-78.4) in close asymptomatic contacts, respectively. Sensitivity was systematically higher in samples yielding positive PCR results with Ct ≤ 20.

DISCUSSION

We found considerable test-to-test antigen detection variations among patients with clinical suspicion of COVID-19 and close asymptomatic contacts. Negative antigen results, regardless of the test used, should be confirmed by PCR.

Accuracy of rapid point-of-care antigen-based diagnostics for SARS-CoV-2: An updated systematic review and meta-analysis with meta-regression analyzing influencing factors

BACKGROUND

Comprehensive information about the accuracy of antigen rapid diagnostic tests (Ag-RDTs) for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is essential to guide public health decision makers in choosing the best tests and testing policies. In August 2021, we published a systematic review and meta-analysis about the accuracy of Ag-RDTs. We now update this work and analyze the factors influencing test sensitivity in further detail.

METHODS AND FINDINGS

We registered the review on PROSPERO (registration number: CRD42020225140). We systematically searched preprint and peer-reviewed databases for publications evaluating the accuracy of Ag-RDTs for SARS-CoV-2 until August 31, 2021. Descriptive analyses of all studies were performed, and when more than 4 studies were available, a random-effects meta-analysis was used to estimate pooled sensitivity and specificity with reverse transcription polymerase chain reaction (RT-PCR) testing as a reference. To evaluate factors influencing test sensitivity, we performed 3 different analyses using multivariable mixed-effects meta-regression models. We included 194 studies with 221,878 Ag-RDTs performed. Overall, the pooled estimates of Ag-RDT sensitivity and specificity were 72.0% (95% confidence interval [CI] 69.8 to 74.2) and 98.9% (95% CI 98.6 to 99.1). When manufacturer instructions were followed, sensitivity increased to 76.3% (95% CI 73.7 to 78.7). Sensitivity was markedly better on samples with lower RT-PCR cycle threshold (Ct) values (97.9% [95% CI 96.9 to 98.9] and 90.6% [95% CI 88.3 to 93.0] for Ct-values <20 and <25, compared to 54.4% [95% CI 47.3 to 61.5] and 18.7% [95% CI 13.9 to 23.4] for Ct-values ≥25 and ≥30) and was estimated to increase by 2.9 percentage points (95% CI 1.7 to 4.0) for every unit decrease in mean Ct-value when adjusting for testing procedure and patients' symptom status. Concordantly, we found the mean Ct-value to be lower for true positive (22.2 [95% CI 21.5 to 22.8]) compared to false negative (30.4 [95% CI 29.7 to 31.1]) results. Testing in the first week from symptom onset resulted in substantially higher sensitivity (81.9% [95% CI 77.7 to 85.5]) compared to testing after 1 week (51.8%, 95% CI 41.5 to 61.9). Similarly, sensitivity was higher in symptomatic (76.2% [95% CI 73.3 to 78.9]) compared to asymptomatic (56.8% [95% CI 50.9 to 62.4]) persons. However, both effects were mainly driven by the Ct-value of the sample. With regards to sample type, highest sensitivity was found for nasopharyngeal (NP) and combined NP/oropharyngeal samples (70.8% [95% CI 68.3 to 73.2]), as well as in anterior nasal/mid-turbinate samples (77.3% [95% CI 73.0 to 81.0]). Our analysis was limited by the included studies' heterogeneity in viral load assessment and sample origination.

CONCLUSIONS

Ag-RDTs detect most of the individuals infected with SARS-CoV-2, and almost all (>90%) when high viral loads are present. With viral load, as estimated by Ct-value, being the most influential factor on their sensitivity, they are especially useful to detect persons with high viral load who are most likely to transmit the virus. To further quantify the effects of other factors influencing test sensitivity, standardization of clinical accuracy studies and access to patient level Ct-values and duration of symptoms are needed.

Rapid screening of SARS-CoV-2 infection: Good performance of nasopharyngeal and Nasal Mid-Turbinate swab for antigen detection among symptomatic and asymptomatic individuals

Although the nasopharyngeal swab (NPS) is considered the gold standard for the diagnosis of the SARS-CoV-2 infection, the Nasal Mid-Turbinate swab (NMTS) is often used due to its higher tolerance among patients. We compared the diagnostic performance of the NPS and the NMTS for the Panbio™ COVID-19 antigen-detecting rapid diagnostic test (Ag-RDT). Two hundred and forty-three individuals were swabbed three times by healthcare professionals: a NMTS and a NPS specimen for the Ag-RDT and an oropharyngeal swab for real time RT-PCR. Forty-nine participants were RNA-SARS-CoV-2 positive by real time RT-PCR: 45 and 40 were positive by the Ag-RDT with NPS and NMTS, respectively. The overall sensitivity and specificity were 91.8% (95% CI: 83.2–100.0) and 99.5% (95% CI: 98.2–100.0) for Ag-RDT with NPS, and 81.6% (95% CI: 69.8–93.5) and 100.0% (95% CI: 99.7–100.0) for the Ag-RDT with NMTS. The Cohen’s kappa index was 0.92 (95% CI: 0.85–0.98). Among asymptomatic individuals, the Ag-RDT with both sampling techniques showed a high sensitivity [100.0% (95% CI: 95.5–100.0) with NPS; 90.9% (95% CI: 69.4–100.0) with NMTS], while the performance of the test decreased in samples with Ct≥ 30 and in patients tested after the first 7 days from symptom onset. Although the NMTS yielded a lower sensitivity compared to NPS, it might be considered a reliable alternative, as it presents greater adherence among patients, enabling scaling of antigen testing strategies, particularly in countries with under-resourced health systems.

Performance Evaluation of the STANDARDTM Q COVID-19 and PanbioTM COVID-19 Antigen Tests in Detecting SARS-CoV-2 during High Transmission Period in Mozambique

(1) Background: Laboratory-based molecular assays are the gold standard to detect SARS-CoV-2. In resource-limited settings, the implementation of these assays has been hampered by operational challenges and long turnaround times. Rapid antigen detection tests are an attractive alternative. Our aim is to evaluate the clinical performance of two SARS-CoV-2 rapid antigen tests during a high transmission period. (2) Methods: A total of 1277 patients seeking SARS-CoV-2 diagnosis were enrolled at four health facilities. Nasopharyngeal swabs for rapid antigen and real time PCR testing were collected for each patient. Sensitivity, specificity, positive and negative predictive values, misclassification rate, and agreement were determined. (3) Results: The overall sensitivity of Panbio COVID-19 was 41.3% (95% CI: 34.6-48.4%) and the specificity was 98.2% (95% CI: 96.2-99.3%). The Standard Q had an overall sensitivity and specificity of 45.0% (95% CI: 39.9-50.2%) and 97.6% (95% CI: 95.3-99.0%), respectively. The positive predictive value of a positive test was 93.3% and 95.4% for the Panbio and Standard Q Ag-RDTs, respectively. A higher sensitivity of 43.2% and 49.4% was observed in symptomatic cases for the Panbio and Standard Q Ag-RDTs, respectively. (4) Conclusions: Despite the overall low sensitivity, the two evaluated rapid tests are useful to improve the diagnosis of symptomatic SARS-CoV-2 infections during high transmission periods.

Diagnostic accuracy of a rapid diagnostic test for the early detection of COVID-19

OBJECTIVES

This study was undertaken to evaluate the diagnostic performance of the BinaxNOW COVID-19 Ag Card rapid antigen assay (Abbott; Chicago, IL, USA) in the detection of COVID-19 infection compared to the reference standard of PCR testing.

METHODS

We evaluated the BinaxNOW COVID-19 Ag Card rapid antigen assay relative to a standard reference PCR test. We tested 3810 nasal swabs from symptomatic and asymptomatic adults undergoing surveillance COVID-19 testing at Howard University using one swab for each nostril. One swab was tested using the rapid antigen assay and the other using the PCR test.

RESULTS

The sensitivity of the BinaxNOW COVID-19 Ag Card rapid antigen assay was 91.84% (95% confidence interval (CI): 80.40-97.73%) and the specificity was 99.95% (95% CI: 99.81-99.99%). The range of Ct values for the N gene was 10.74-34.90 (M = 26.88, SD=4.86). Fourteen (28.6%) samples had an N gene Ct value > 30. The average N gene Ct value for rapid test negative (i.e. false negative) samples was 31.92.

CONCLUSIONS

The sensitivity of the test in our symptomatic and asymptomatic cohort was lower than the manufacturer's reported sensitivity in a symptomatic cohort (97.1%). Despite their relatively lower sensitivity (especially in asymptomatic individuals), rapid tests have undeniable benefits (i.e., ease of use and rapid results) that make them a helpful tool in the control of the SARS-CoV-2 pandemic. Given the diagnostic accuracy of these tests as evidenced by this study, rapid tests can be thoughtfully employed in situations where swift results are critical.

Performance of Rapid Antigen Tests for COVID-19 Diagnosis: A Systematic Review and Meta-Analysis

The identification of viral RNA using reverse transcription quantitative polymerase chain reaction (RT-qPCR) is the gold standard for identifying an infection caused by SARS-CoV-2. The limitations of RT-qPCR such as requirement of expensive instruments, trained staff and laboratory facilities led to development of rapid antigen tests (RATs). The performance of RATs has been widely evaluated and found to be varied in different settings. The present systematic review aims to evaluate the pooled sensitivity and specificity of the commercially available RATs. This review was registered on PROSPERO (registration number: CRD42021278105). Literature search was performed through PubMed, Embase and Cochrane COVID-19 Study Register to search studies published up to 26 August 2021. The overall pooled sensitivity and specificity of RATs and subgroup analyses were calculated. Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) was used to assess the risk of bias in each study. The overall pooled sensitivity and specificity of RATs were 70% (95% CI: 69–71) and 98% (95% CI: 98–98), respectively. In subgroup analyses, nasal swabs showed the highest sensitivity of 83% (95% CI: 80–86) followed by nasopharyngeal swabs 71% (95% CI: 70–72), throat swabs 69% (95% CI: 63–75) and saliva 68% (95% CI: 59–77). Samples from symptomatic patients showed a higher sensitivity of 82% (95% CI: 82–82) as compared to asymptomatic patients at 68% (95% CI: 65–71), while a cycle threshold (Ct) value ≤25 showed a higher sensitivity of 96% (95% CI: 95–97) as compared to higher Ct value. Although the sensitivity of RATs needs to be enhanced, it may still be a viable option in places where laboratory facilities are lacking for diagnostic purposes in the early phase of disease.

COVID-19 Diagnosis: Current and Future Techniques

COVID-19 pandemic continues to be a global threat, affecting more than 200 countries/territories at both human and economic level. This necessitates the rapid development of highly reliable diagnostic methods in order to effectively and accurately diagnose the pathology to prevent the spread of COVID-19. Currently, RT-PCR is the most widely used method worldwide for SARS-CoV-2 detection. Serological assays are being used for sero-surveys of SARS-CoV-2 antibody prevalence in the community. Radiology imaging has been useful in the clinical diagnosis of COVID-19. These methods have their own limitations and there are continued efforts to develop easier, economic, highly sensitive and specific, point-of-care methods. Reverse transcription-loop mediated isothermal amplification (RT-LAMP), nucleic acid sequence-based amplification (NASBA), CRISPR-Cas-based detection, and digital PCR are such techniques being employed in research laboratories, with many awaiting diagnostic approval from competent authorities. This review highlights the rapidly expanding array of existing and in-development diagnostic tests/strategies that may be used to diagnose SARS-CoV-2 infection in both clinical and research settings.

High-Affinity Dimeric Aptamers Enable the Rapid Electrochemical Detection of Wild-Type and B.1.1.7 SARS-CoV-2 in Unprocessed Saliva

We report a simple and rapid saliva-based SARS-CoV-2 antigen test that utilizes a newly developed dimeric DNA aptamer, denoted as DSA1N5, that specifically recognizes the spike proteins of the wildtype virus and its Alpha and Delta variants with dissociation constants of 120, 290 and 480 pM, respectively, and binds pseudotyped lentiviruses expressing the wildtype and alpha trimeric spike proteins with affinity constants of 2.1 pM and 2.3 pM, respectively. To develop a highly sensitive test, DSA1N5 was immobilized onto gold electrodes to produce an electrochemical impedance sensor, which was capable of detecting 1000 viral particles per mL in 1:1 diluted saliva in under 10 min without any further sample processing. Evaluation of 36 positive and 37 negative patient saliva samples produced a clinical sensitivity of 80.5 % and specificity of 100 % and the sensor could detect the wildtype virus as well as the Alpha and Delta variants in the patient samples, which is the first reported rapid test that can detect any emerging variant of SARS-CoV-2.

Rapid antigen tests for the detection of SARS-CoV-2: A narrative review

The rapid identificationand isolation of COVID-19 patients has become the cornerstone for the control of the recent outbreak. Real-time quantitative polymerase chain reaction is routinely used to confirm COVID-19 diagnosis and is considered the gold standard due to high sensitivity and specificity. Nevertheless, it usually takes several days and a relatively higher cost. Antigen tests based have emerged to cope with such disadvantages, by offering rapid results, an easy-to-use procedure, and low costs. The objective of the narrative review was to provide up-to-date data about CE-marked rapid antigen tests (RATs) for COVID-19. Given their large number, the study only focused on representative and widely used in Spain (Standard Q, Nadal, Panbio, CerTest, and Wondfo). RATs have become a very useful and validated tool for controlling the spread of COVID-19 allowing the rapid identification of active infection and isolation of positive patients. The present revision of the literature has demonstrated that sensitivity and specificity of all available RATs in Spain are high and accomplish European regulations and WHO recommendations.

Development of surface-enhanced Raman scattering-based immunoassay platforms using hollow Au nanostars for reliable SARS-CoV-2 diagnosis

We developed a novel surface‐enhanced Raman scattering (SERS)‐based SARS‐CoV‐2 assay platform using hollow Au nanostars to realize high‐sensitivity diagnosis of SARS‐CoV‐2. The assay was performed using SARS‐CoV‐2 lysate as the target in a wide dynamic range with virus concentrations ranging from 0 to 10⁴ PFU/ml and has a limit of detection (LOD) of 5.1 PFU/ml. This LOD value shows 100 times and 10 times better sensitivity compared to the LODs measured on the same sample using a commercially available rapid kit and enzyme‐linked immunosorbent assay, respectively. Therefore, we believe that this SERS‐based SARS‐CoV‐2 assay platform has high diagnostic accuracy for early or asymptomatic infected patients with low virus concentrations. Furthermore, the probability of a false‐negative diagnosis is likely to be very low.

Screening for SARS-CoV-2 infection in asymptomatic individuals using the Panbio COVID-19 antigen rapid test (Abbott) compared with RT-PCR: a prospective cohort study

BACKGROUND

Antigen-based point-of-care tests for identification of SARS-CoV-2 may markedly enhance effectiveness of population-based controlling strategies. Previous studies have demonstrated >70% sensitivity and high specificity compared with reverse transcriptase real-time PCR (RT-PCR) in symptomatic individuals, but test performance for asymptomatic individuals is unknown.

METHODS

Test performance of the Panbio COVID-19 Ag Rapid Test (Abbott) was compared with RT-PCR in a longitudinal cohort study of asymptomatic football players and staff members of professional football clubs. Based on timing of symptoms and prior and subsequent test results, positive RT-PCR tests were categorised as presymptomatic, early or late infection, or persistent RNA shedding.

FINDINGS

2425 tests were performed in 824 individuals, of which 52 (6.3%) were SARS-CoV-2 positive based on RT-PCR. There were 2406 paired sets from asymptomatic subjects for analysis. Sixteen Panbio tests were inconclusive, for which sensitivity analyses were performed (considering results as either positive or negative or being excluded). Sensitivity of Panbio for screening of asymptomatic individuals ranged from 80.0% (61.4-92.3) to 86.67% (69.2-96.2) and specificity from 99.53% (95% CI 99.2 to 99.8) to 100% (95% CI 99.8 to 100). Sensitivity of Panbio to detect subjects with presymptomatic/early infection (n=42) ranged from 81.82% (95% CI 67.3 to 91.8) to 90.91% (95% CI 78.3 to 97.5) with specificity always above 99%.

INTERPRETATION

The Panbio COVID-19 Ag rapid test identifies 81%-90% of presymptomatic and early asymptomatic SARS-CoV-2 infections with high specificity. This test may therefore be adopted in testing strategies such as targeted screening of specific populations where prevalence is low.

IFCC interim guidelines on rapid point-of-care antigen testing for SARS-CoV-2 detection in asymptomatic and symptomatic individuals

With an almost unremittent progression of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections all around the world, there is a compelling need to introduce rapid, reliable, and high-throughput testing to allow appropriate clinical management and/or timely isolation of infected individuals. Although nucleic acid amplification testing (NAAT) remains the gold standard for detecting and theoretically quantifying SARS-CoV-2 mRNA in various specimen types, antigen assays may be considered a suitable alternative, under specific circumstances. Rapid antigen tests are meant to detect viral antigen proteins in biological specimens (e.g. nasal, nasopharyngeal, saliva), to indicate current SARS-CoV-2 infection. The available assay methodology includes rapid chromatographic immunoassays, used at the point-of-care, which carries some advantages and drawbacks compared to more conventional, instrumentation-based, laboratory immunoassays. Therefore, this document by the International Federation for Clinical Chemistry and Laboratory Medicine (IFCC) Taskforce on COVID-19 aims to summarize available data on the performance of currently available SARS-CoV-2 antigen rapid detection tests (Ag-RDTs), providing interim guidance on clinical indications and target populations, assay selection, and evaluation, test interpretation and limitations, as well as on pre-analytical considerations. This document is hence mainly aimed to assist laboratory and regulated health professionals in selecting, validating, and implementing regulatory approved Ag-RDTs.

Diagnostic accuracy of Panbio rapid antigen tests on oropharyngeal swabs for detection of SARS-CoV-2

BACKGROUND

Antigen-detecting rapid diagnostic tests (Ag-RDTs) for the detection of SARS-CoV-2 offer new opportunities for testing in the context of the COVID-19 pandemic. Nasopharyngeal swabs (NPS) are the reference sample type, but oropharyngeal swabs (OPS) may be a more acceptable sample type in some patients.

METHODS

We conducted a prospective study in a single screening center to assess the diagnostic performance of the Panbio™ COVID-19 Ag Rapid Test (Abbott) on OPS compared with reverse-transcription quantitative PCR (RT-qPCR) using NPS during the second pandemic wave in Switzerland.

RESULTS

402 outpatients were enrolled in a COVID-19 screening center, of whom 168 (41.8%) had a positive RT-qPCR test. The oropharyngeal Ag-RDT clinical sensitivity compared to nasopharyngeal RT-qPCR was 81% (95%CI: 74.2-86.6). Two false positives were noted out of the 234 RT-qPCR negative individuals, which resulted in a clinical specificity of 99.1% (95%CI: 96.9-99.9) for the Ag-RDT. For cycle threshold values ≤ 26.7 (≥ 1E6 SARS-CoV-2 genomes copies/mL, a presumed cut-off for infectious virus), 96.3% sensitivity (95%CI: 90.7-99.0%) was obtained with the Ag-RDT using OPS.

INTERPRETATION

Based on our findings, the diagnostic performance of the Panbio™ Covid-19 RDT with OPS samples, if taken by a trained person and high requirements regarding quality of the specimen, meet the criteria required by the WHO for Ag-RDTs (sensitivity ≥80% and specificity ≥97%) in a high incidence setting in symptomatic individuals.

Validation and implementation of the Panbio COVID-19 Ag rapid test for the diagnosis of SARS-CoV-2 infection in symptomatic hospital healthcare workers

BACKGROUND

RT-PCR is the current recommended laboratory method to diagnose SARS-CoV-2 in healthcare workers (HCW). As RT-PCR is not widely available and is time-consuming, it limits decision making on removal from and return to work of possibly contagious HCW.

AIM

In this study we evaluated the Panbio™ COVID-19 Ag rapid test (PanbioCAgRT) in 825 hospital HCW.

METHODS AND FINDING

This study consisted of two phases. In the validation phase, we tested hospital HCW with mild symptoms (three days or less) in parallel using the PanbioCAgRT and the RT-qPCR test. The PanbioCAgRT demonstrated 86.7% sensitivity, 100% specificity, 100% PPV and 98.5% NPV with regard to RT-qPCR. For HCW with PanbioCAgRT-/RT-qPCR+, the median Ct value was 30.9, whereas for the HCW with PanbioCAgRT+/RT-qPCR+ the median Ct value was 19.3 (P<0.001). In the second phase, we implemented an on-site antigen test-based strategy for symptomatic hospital HCW: HCW that tested positive with the PanbioCAgRT on-site were considered SARS-CoV-2 positive and were sent home. HCW that tested negative with the PanbioCAgRT on-site were allowed to work with PPE pending RT-qPCR test results from the laboratory. Sensitivity of the antigen test-based strategy was 72.5% and NPV was 97%. For HCW with PanbioCAgRT-/RT-qPCR+ median Ct values were 27.8.

CONCLUSION

The PanbioCAgRTt validated in this study showed a high sensitivity and specificity in samples obtained from HCW with high viral loads. The antigen-based testing strategy proposed in this study seems to be effective, safe and easy to implement in a wide range of occupational healthcare settings.

Accuracy of the Mologic COVID-19 rapid antigen test: a prospective multi-centre analytical and clinical evaluation

Background: The coronavirus disease 2019 (COVID-19) pandemic has highlighted the reliance on antigen detection rapid diagnostic tests (Ag-RDTs). Their evaluation at point of use is a priority. Methods: Here, we report a multi-centre evaluation of the analytical sensitivity, specificity, and clinical accuracy of the Mologic COVID-19 Ag-RDT by comparing to reverse transcriptase polymerase chain reaction (RT-qPCR) results from individuals with and without COVID-19 symptoms. Participants had attended hospitals in Merseyside, hospital and ambulance services in Yorkshire, and drive-through testing facilities in Northumberland, UK. Results: The limit of detection of the Mologic COVID-19 Ag-RDT was 5.0 x 102 pfu/ml in swab matrix with no cross-reactivity and interference for any other pathogens tested. A total of 347 participants were enrolled from 26th of November 2020 to 15th of February 2021 with 39.2% (CI 34.0-44.6) testing RT-qPCR positive for SARS-CoV-2. The overall sensitivity and specificity of the Mologic Ag-RDT compared to the reference SARS-CoV-2 RT-qPCR were 85.0% (95% CI 78.3-90.2) and 97.8% (95.0-99.3), respectively. Sensitivity was stratified by RT-qPCR cycle threshold (Ct) and 98.4% (91.3-100) of samples with a Ct less than 20 and 93.2% (86.5-97.2) of samples with a Ct less than 25 were detected using the Ag-RDT. Clinical accuracy was stratified by sampling strategy, swab type and clinical presentation. Mologic COVID-19 Ag-RDT demonstrated highest sensitivity with nose/throat swabs compared with throat or nose swabs alone; however, the differences were not statistically significant. Conclusions: Overall, the Mologic test had high diagnostic accuracy across multiple different settings, different demographics, and on self-collected swab specimens. These findings suggest the Mologic rapid antigen test may be deployed effectively across a range of use settings.

[Internal validity of a rapid test for COVID-19 antigens in a nursing home]

Introducción

La RT-qPCR es la prueba de referencia para la detección de la infección por SARS-CoV-2; sin embargo, en la actualidad se dispone de pruebas rápidas de detección de antígenos (PRDA). En este trabajo se evaluó la validez interna de la PRDA en el contexto de un brote en una residencia de mayores.

Métodos

Se analizaron muestras de exudado nasofaríngeo mediante PRDA y RT-qPCR de 61 residentes de una residencia de mayores. Se calculó la sensibilidad y especificidad de la PRDA con respecto a la RT-qPCR.

Resultados

La especificidad fue del 100% (IC 95% 54,1-100,0), mientras que la sensibilidad en asintomáticos fue del 70,3% (IC 95% 53,0-84,1) y en los sintomáticos del 83,3% (IC 95% 51,6-97,9).

Conclusiones

Las PRDA son lo suficientemente sensibles y específicas para ser utilizadas como pruebas de cribado en las residencias de mayores, especialmente es situación de brotes o sospecha del mismo por la presencia de sintomáticos.

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

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