Evaluation of Efficacy of Rapid Antigen Test against RT-PCR and its Correlation with Cycle Threshold (CT) values: an Institutional Experience

Rapidly increasing COVID-19 or SARS-CoV-2 in whole world caused a tremendous pressure on existing diagnostic setup to give accurate diagnosis on time by gold standard RT-PCR technique forcing scientist to think beyond RT-PCR which ultimately ended with invent of Rapid antigen test which can give about 100% specific and rapid result but may miss many case due to low sensitivity. So we wanted to evaluate the Rapid antigen test against RT-PCR for its diagnostic accuracy. We followed standard procedure for sample collection, Rapid antigen test and RT-PCR test. In about one and half month span we collected 554 antigen negative samples in our hospital. About 13% sample (74/554) turned out as positive by RT-PCR test. About 40 % (30/74) positive samples had low Ct value (<25) indicating higher viral load present in those patients. Above findings indicate that only antigen test will miss a significant portion of positive cases with higher viral load which may complicate the pandemic by unknowingly spreading the virus within the society. So we should try to improve our infrastructure to carry out more RTPCR test so we can detect more cases to identify and isolate them from others to prevent or slowdown the transmission chain.

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The value of anal swab RT-PCR for COVID-19 diagnosis in adult Indonesian patients

BMJ Open Gastroenterology ◽

10.1136/bmjgast-2020-000590 ◽

2021 ◽

Vol 8 (1) ◽

pp. e000590

Author(s):

Murdani Abdullah ◽

Dedy Gunawanjati Sudrajat ◽

Virly Nanda Muzellina ◽

Juferdy Kurniawan ◽

Aulia Rizka ◽

...

Keyword(s):

Clinical Laboratory ◽

Gastrointestinal Symptoms ◽

High Specificity ◽

Nasopharyngeal Swab ◽

Rt Pcr ◽

Severe Condition ◽

Hospitalised Patients ◽

Anal Swab ◽

Low Sensitivity ◽

Pcr Test

ObjectiveThis study will test the performance of the anal swab PCR test when compared with the nasopharyngeal swab PCR test as a diagnostic tool for COVID-19.DesignAn observational descriptive study which included hospitalised suspected, or probable cases of hopitalised COVID-19 patients, conducted in Dr. Cipto Mangunkusumo National Hospital, Ciputra Hospital, Mitra Keluarga Depok Hospital and Mitra Keluarga Kelapa Gading Hospital, Indonesia. Epidemiological, clinical, laboratory and radiology data were obtained. Nasopharyngeal and anal swabs specimens were collected for SARS-CoV-2 RNA detection.ResultsWe analysed 136 subjects as part of this study. The clinical spectrum of COVID-19 manifesation in this study was typical of hospitalised patients, with 25% classified as mild cases, 14.7% in severe condition and 12.5% of subjects classified as having acute respiratory distress syndrome. When compared with nasopharyngeal swab as the standard specimen for reverse transcription polymerase chain reaction (RT-PCR) detection of SARS-CoV-2 antigen, the sensitivity and specificity of the anal swab was 36.7% and 93.8%, respectively. The positive and negative predictive value were 97.8% and 16.5 %, respectively. The performance of the anal swab remained similar when only the subgroup of patients with gastrointestinal symptoms (n=92, 67.6%) was analysed (sensitivity 40% and specificity 91.7%). Out of all the subjects included in analysis, 67.6% had gastrointestinal symptoms. Similarly, 73.3% of patients in the anal swab-positive group had gastrointestinal symptoms. The two most common gastrointestinal symptoms in the subjects’ population were nausea and anorexia.ConclusionAnal swab specimen has low sensitivity (36.7%) but high specificity (93.8%) for detecting SARS-CoV-2 antigen by RT-PCR. Only one additional positive result was found by anal swab among the nasopharyngeal swab-negative group. Anal swab may not be needed as an additional test at the beginning of a patient’s diagnostic investigation and nasopharyngeal swab RT-PCR remains as the standard diagnostic test for COVID-19.

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High Sensitivity and NPV for BinaxNOW Rapid Antigen Test in Children at a Mass Testing Site During Prevalent Delta Variant

10.1101/2022.01.05.22268788 ◽

2022 ◽

Author(s):

Kristie J Sun ◽

Mary Jane E Vaeth ◽

Matthew L Robinson ◽

Maryam Elhabashy ◽

Ishaan Gupta ◽

...

Keyword(s):

Predictive Value ◽

High Sensitivity ◽

High Volume ◽

Educational Opportunities ◽

Antigen Test ◽

Sample Collection ◽

Rt Pcr ◽

Polymerase Chain ◽

Testing Site ◽

Antigen Tests

SARS-CoV-2 continues to develop new, increasingly infectious variants, such as delta and omicron. Here, we evaluate the efficacy of the Abbott BinaxNOW Rapid Antigen Test against the gold standard of Reverse Transcription Polymerase Chain Reaction (RT-PCR) in 1054 pediatric participants presenting to a state-owned high-volume Coronavirus Disease 2019 (COVID-19) testing site. During the testing period, the delta variant was predominant. Prior to sample collection, symptomatic and exposure status was collected for all participants based on Centers for Disease Control (CDC) criteria. RT-PCR results demonstrated an overall prevalence rate of 5.2%. For all participants, the sensitivity of the rapid antigen tests was 92.7% (95% CI 82.4% - 98.0%) and specificity was 98.0% (95% CI 97.0%-98.8%). For symptomatic participants, the sensitivity was 92.3% (95% CI 74.9% - 99.1%), specificity was 96.6% (95% CI 93.6%- 98.4%), positive predictive value (PPV) was 72.7% (95% CI 54.5% - 86.7%) and negative predictive value (NPV) was 99.2% (95% CI 98.2% - 100%). Among asymptomatic participants, the sensitivity was 92.6% (95% CI 75.7% - 99.1%), specificity was 98.6% (95% CI 97.5% - 99.3%) the PPV was 71.4% (95% CI 53.7% - 85.4%) and the NPV was 99.7% (95% CI 99.0% - 100%). Our reported sensitivity and NPV are higher than other pediatric studies, but specificity and PPV are lower. Importance Children are especially impacted by the disease and its ability to disrupt educational opportunities. Although vaccinations have been approved for children 5 years and older, many children remain unvaccinated. Widespread testing may improve the ability for children to remain in in-person activities, minimizing absences from school and extracurriculars. Highly accurate rapid antigen tests may be vital to containing future COVID-19 waves while mitigating detrimental effects.

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Clinical Evaluation of a Combo Rapid Antigen Test QuickNavi-Flu+COVID19 Ag for Simultaneous Detection of SARS-CoV-2 and Influenza Viruses

10.1101/2021.12.05.21267215 ◽

2021 ◽

Author(s):

Yuto Takeuchi ◽

Yusaku Akashi ◽

Yoshihiko Kiyasu ◽

Norihiko Terada ◽

Yoko Kurihara ◽

...

Keyword(s):

Real Time ◽

Sensitivity And Specificity ◽

Clinical Performance ◽

Simultaneous Detection ◽

Influenza Viruses ◽

Antigen Test ◽

Sample Collection ◽

Rt Pcr ◽

The Real ◽

Reverse Transcription Pcr

AbstractIntroductionSince respiratory sample collection is an uncomfortable experience, simultaneous detection of pathogens with a single swab is preferable. We prospectively evaluated the clinical performance of a newly developed antigen test QuickNavi-Flu+COVID19 Ag (Denka Co., Ltd., Tokyo, Japan) which can detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza viruses at the same time with a single testing device.MethodsIncluded were those who were suspected of contracting coronavirus disease 2019 (COVID-19) and referred to a PCR center at Ibaraki prefecture in Japan, between August 2, 2021 to September 13, 2021, when the L452R mutant strains of SARS-CoV-2 were prevalent. Additional nasopharyngeal samples and anterior nasal samples were obtained for the antigen test and were compared with a reference reverse transcription PCR (RT-PCR) using nasopharyngeal samples.ResultsIn total, 1510 nasopharyngeal samples and 862 anterior nasal samples were evaluated. For SARS-CoV-2 detection in nasopharyngeal samples, the sensitivity and specificity of the antigen test were 80.9% and 99.8%, respectively. The sensitivity and specificity using anterior nasal samples were 67.8% and 100%, respectively. In symptomatic cases, the sensitivities increased to 88.3% with nasopharyngeal samples and 73.7% with anterior nasal samples. There were three cases of discrepant results between the antigen test and the real-time RT-PCR. All of them were positive with the antigen test but negative with the real-time RT-PCR in SARS-CoV-2 detection. During the study period, influenza viruses were not detected.ConclusionA combo kit, QuickNavi-Flu+COVID19 Ag, showed an acceptable sensitivity and sufficient specificity for SARS-CoV-2 detection, especially using nasopharyngeal sample collected from symptomatic patients.

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Clinical evaluation of the Roche/SD Biosensor rapid antigen test with symptomatic, non-hospitalized patients in a municipal health service drive-through testing site

10.1101/2020.11.18.20234104 ◽

2020 ◽

Cited By ~ 5

Author(s):

Zsὁfia Iglὁi ◽

Jans Velzing ◽

Janko van Beek ◽

David van de Vijver ◽

Georgina Aron ◽

...

Keyword(s):

Viral Load ◽

Rapid Test ◽

Contact Tracing ◽

Gene Copy ◽

Nasopharyngeal Swab ◽

List Type ◽

Antigen Test ◽

Rt Pcr ◽

Outbreak Management ◽

Testing Site

AbstractBackgroundRapid detection of infectious individuals is essential in stopping the further spread of SARS-CoV-2. Although rapid antigen test is not as sensitive as the gold standard RT-PCR, the time to result is decreased by day(s), strengthening the effectiveness of contact tracing.MethodsThe Roche/SD Biosensor lateral flow antigen rapid test was evaluated in a mild symptomatic population at a large drive through testing site. A second nasopharyngeal swab was directly tested with the rapid test on site and results were compared to RT-PCR and virus culture. Date of onset and symptoms were analysed using data from a clinical questionnaire.ResultsWe included 970 persons with complete data. Overall sensitivity and specificity were 84.9% (CI95% 79.1-89.4) and 99.5% (CI95% 98.7-99.8) which translated into a positive predictive value of 97.5% (CI95% 94.0-99.5) under the current regional PCR positivity of 19.2%. Sensitivity for people with high loads of viral RNA (ct <30, 2.17E+05 E gene copy/ml) and who presented within 7 days since symptom onset increased to 95.8% (CI95% 90.5-98.2). Band intensity and time to result correlated strongly with viral load thus strong positive bands could be read before the recommended time. Around 98% of all viable specimen with ct <30 were detected successfully indicating that the large majority of infectious people can be captured with this test.ConclusionAntigen rapid tests can detect mildly symptomatic cases in the early phase of disease thereby identifying the most infectious individuals. Using this assay can have a significant value in the speed and effectiveness of SARS-CoV-2 outbreak management.SummaryPeople with early onset and high viral load were detected with 98.2% sensitivity.97% of individuals in which virus could be cultured were detected by the rapid test.This test is suitable to detect mild symptomatic cases.

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Performance characteristics of a rapid SARS-CoV-2 antigen detection assay at a public plaza testing site in San Francisco

10.1101/2020.11.02.20223891 ◽

2020 ◽

Cited By ~ 2

Author(s):

Genay Pilarowski ◽

Paul Lebel ◽

Sara Sunshine ◽

Jamin Liu ◽

Emily Crawford ◽

...

Keyword(s):

Viral Load ◽

San Francisco ◽

High Viral Load ◽

Performance Characteristics ◽

Viral Rna ◽

Antigen Test ◽

Rt Pcr ◽

Detection Assay ◽

Community Transmission ◽

Testing Site

ABSTRACTWe evaluated the performance of the Abbott BinaxNOW™ Covid-19 rapid antigen test to detect virus among persons, regardless of symptoms, at a public plaza site of ongoing community transmission. Titration with cultured clinical SARS-CoV-2 yielded a human observable threshold between 1.6×104-4.3×104 viral RNA copies (cycle threshold (Ct) of 30.3-28.8 in this assay). Among 878 subjects tested, 3% (26/878) were positive by RT-PCR, of which 15/26 had a Ct<30, indicating high viral load. 40% (6/15) of Ct<30 were asymptomatic. Using this Ct<30 threshold for Binax-CoV2 evaluation, the sensitivity of the Binax-CoV2 was 93.3% (14/15), 95% CI: 68.1-99.8%, and the specificity was 99.9% (855/856), 95% CI: 99.4-99.9%.

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Should Chest X-ray Be Used in Diagnosing COVID-19?

Acta Medica Philippina ◽

10.47895/amp.v54i0.2569 ◽

2020 ◽

Vol 54 ◽

Author(s):

Maria Cristina Z. San Jose ◽

Valentin C. Dones

Keyword(s):

British Society ◽

Normal Lung ◽

Rt Pcr ◽

Thoracic Imaging ◽

X Ray ◽

Canadian Association ◽

Lung Abnormalities ◽

Chest X Ray ◽

Low Sensitivity ◽

Pcr Test

While chest x-ray is readily available and may precede RT-PCR test, chest x-ray has low sensitivity early in the COVID-19 disease and shows non-specific lung abnormalities in COVID-19 patients. Chest x-ray is part of the initial diagnostic tool used on COVID-19 patients in some hospitals as it yields fast results compared with reverse transcription-polymerase chain reaction (RT-PCR). Chest Computed Tomography (CT) has been reported to be more sensitive than chest x-ray in determining the presence of COVID-19. Chest x-ray findings in confirmed COVID-19 patients show:  Normal lung findings early in the illness and in mildly symptomatic patients Typical ground-glass opacities and consolidation in the lung periphery Lung abnormalities are non-specific and may likewise be present in other infections and coronavirus-types of pneumonia The American College of Radiology (ACR), Center for Disease Control and Prevention (CDC), Canadian Association of Radiologists (CAR), Canadian Society of Thoracic Radiology (CSTR), and British Society of Thoracic Imaging do not recommend the use of chest x-ray to diagnose COVID-19. The Fleisher Society, composed of radiologists and pulmonologists in ten countries, does not recommend a chest x-ray for patients suspected of mild COVID-19. A chest x-ray is recommended for patients with moderate to severe COVID-19 needing immediate triage and patients at high risk for disease progression. Despite presence of chest x-ray findings suggesting COVID-19, RT-PCR test remains the standard diagnostic procedure.

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Diagnosis, clinical characteristics, and outcomes of COVID-19 patients from a large healthcare system in northern New Jersey

Scientific Reports ◽

10.1038/s41598-021-83959-7 ◽

2021 ◽

Vol 11 (1) ◽

Cited By ~ 1

Author(s):

Yanan Zhao ◽

Marcus H. Cunningham ◽

Jose R. Mediavilla ◽

Steven Park ◽

Sean Fitzgerald ◽

...

Keyword(s):

New Jersey ◽

Viral Load ◽

Clinical Characteristics ◽

Medical Center ◽

Case Series ◽

The United States ◽

Linear Increase ◽

Rt Pcr ◽

Patient Series ◽

Pcr Test

AbstractNew Jersey was an early epicenter for the COVID-19 pandemic in the United States, yet information on hospitalized COVID-19 patients from this area is scarce. This study aimed to provide data on demographics and clinical features of a hospitalized patient population who were confirmed with infection by our in-house (CDI) real-time reverse-transcription polymerase chain reaction (RT-PCR) test. We included consecutive patients who were admitted to Hackensack Meridian Health system hospitals with laboratory-confirmed diagnoses of COVID-19 at Hackensack University Medical Center by the CDI virus test between March 12, 2020, and April 8, 2020. Clinical data and viral testing results were collected and analyzed for characteristics associated with outcomes, as well as the correlation with viral load. A total of 722 patients were included in the study, with a median age of 63 (interquartile range (IQR), 51–75) and 272 (37.7%) females. Mortality of this case series was 25.8%, with a statistically significant linear increase observed from age 40 to ≥ 80 by 10-year intervals. Viral load, as indicated by the cycle of threshold (Ct) values from the RT-PCR test, was significantly higher in the oldest patient group (≥ 80), and inversely correlated with survival. This is the first report to describe the clinical characteristics and outcomes in a large hospitalized COVID-19 patient series from New Jersey. Findings from this study are valuable to the ongoing response of both nationwide healthcare networks and the medical research community.

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Diagnostic performance and characteristics of anterior nasal collection for the SARS-CoV-2 antigen test: a prospective study

Scientific Reports ◽

10.1038/s41598-021-90026-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Yuto Takeuchi ◽

Yusaku Akashi ◽

Daisuke Kato ◽

Miwa Kuwahara ◽

Shino Muramatsu ◽

...

Keyword(s):

Prospective Study ◽

Clinical Utility ◽

Diagnostic Performance ◽

Antigen Test ◽

Sample Collection ◽

Rt Pcr ◽

Reverse Transcription Pcr ◽

Moderate Sensitivity ◽

Testing Site ◽

A Prospective Study

AbstractThe clinical utility of antigen test using anterior nasal samples has not been well evaluated. We conducted a prospective study in a drive-through testing site located at a PCR center to evaluate the diagnostic performance of the antigen test QuickNavi-COVID19 Ag using anterior nasal samples and to compare the degrees of coughs or sneezes induction and the severity of pain between anterior nasal collection and nasopharyngeal collection. The study included a total of 862 participants, of which 91.6% were symptomatic. The median duration from symptom onset to sample collection was 2.0 days. Fifty-one participants tested positive for severe acute respiratory syndrome coronavirus 2 on reverse transcription PCR (RT-PCR) with nasopharyngeal samples, and all of them were symptomatic. In comparison to the findings of RT-PCR, the antigen test using anterior nasal samples showed 72.5% sensitivity (95% confidence interval [CI] 58.3–84.1%) and 100% specificity (95% CI 99.3–100%). Anterior nasal collection was associated with a significantly lower degree of coughs or sneezes induction and the severity of pain in comparison to nasopharyngeal collection (p < 0.001). The antigen test using anterior nasal samples showed moderate sensitivity in symptomatic patients who were at the early stages of the disease course but was less painful and induced fewer coughs or sneezes.

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Evaluation of Antibody Response in Symptomatic and Asymptomatic COVID-19 Patients and Diagnostic Assessment of New IgM/IgG ELISA Kits

Pathogens ◽

10.3390/pathogens10020161 ◽

2021 ◽

Vol 10 (2) ◽

pp. 161

Author(s):

Hadeel T. Al-Jighefee ◽

Hadi M. Yassine ◽

Maryam A. Al-Nesf ◽

Ali A. Hssain ◽

Sara Taleb ◽

...

Keyword(s):

Immune Response ◽

Severe Acute Respiratory Syndrome ◽

Antibody Response ◽

Diagnostic Assessment ◽

Enzyme Linked Immunosorbent Assay ◽

Rt Pcr ◽

Serum Samples ◽

Time Intervals ◽

Low Sensitivity ◽

Pcr Test

This study aims to study the immune response and evaluate the performances of four new IgM and five IgG enzyme-linked immunosorbent assay (ELISA) kits for detecting anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies against different antigens in symptomatic and asymptomatic coronavirus disease 2019 (COVID-19) patients. A total of 291 samples collected from symptomatic and asymptomatic RT–PCR-confirmed patients were used to evaluate the ELISA kits’ performance (EDI, AnshLabs, DiaPro, NovaLisa, and Lionex). The sensitivity was measured at three different time-intervals post symptoms onset or positive SARS-CoV-2 RT–PCR test (≤14, 14–30, >30 days). The specificity was investigated using 119 pre-pandemic serum samples. The sensitivity of all IgM kits gradually decreased with time, ranging from 48.7% (EDI)–66.4% (Lionex) at ≤14 days, 29.1% (NovaLisa)–61.8% (Lionex) at 14–30 days, and 6.0% (AnshLabs)–47.9% (Lionex) at >30 days. The sensitivity of IgG kits increased with time, peaking in the latest interval (>30 days) at 96.6% (Lionex). Specificity of IgM ranged from 88.2% (Lionex)–99.2% (EDI), while IgG ranged from 75.6% (DiaPro)–98.3% (Lionex). Among all RT–PCR-positive patients, 23 samples (7.9%) were seronegative by all IgG kits, of which only seven samples (30.4%) had detectable IgM antibodies. IgM assays have variable and low sensitivity, thus considered a poor marker for COVID-19 diagnosis. IgG assays can miss at least 8% of RT–PCR-positive cases.

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Diagnostic accuracy of rapid antigen tests in asymptomatic and presymptomatic close contacts of individuals with confirmed SARS-CoV-2 infection: cross sectional study

BMJ ◽

10.1136/bmj.n1676 ◽

2021 ◽

pp. n1676

Author(s):

Ewoud Schuit ◽

Irene K Veldhuijzen ◽

Roderick P Venekamp ◽

Wouter van den Bijllaardt ◽

Suzan D Pas ◽

...

Keyword(s):

Viral Load ◽

Cross Sectional Study ◽

Antigen Test ◽

Sectional Study ◽

Rt Pcr ◽

Cross Sectional ◽

Predictive Values ◽

Test Sensitivity ◽

Antigen Tests ◽

Close Contacts

Abstract Objective To assess the diagnostic test accuracy of two rapid antigen tests in asymptomatic and presymptomatic close contacts of people with SARS-CoV-2 infection on day 5 after exposure. Design Prospective cross sectional study. Setting Four public health service covid-19 test sites in the Netherlands. Participants 4274 consecutively included close contacts (identified through test-and-trace programme or contact tracing app) aged 16 years or older and asymptomatic for covid-19 when requesting a test. Main outcome measures Sensitivity, specificity, and positive and negative predictive values of Veritor System (Beckton Dickinson) and Biosensor (Roche Diagnostics) rapid antigen tests, with reverse-transcriptase polymerase chain reaction (RT-PCR) testing as reference standard. The viral load cut-off above which 95% of people with a positive RT-PCR test result were virus culture positive was used as a proxy of infectiousness. Results Of 2678 participants tested with Veritor, 233 (8.7%) had a RT-PCR confirmed SARS-CoV-2 infection of whom 149 were also detected by the rapid antigen test (sensitivity 63.9%, 95% confidence interval 57.4% to 70.1%). Of 1596 participants tested with Biosensor, 132 (8.3%) had a RT-PCR confirmed SARS-CoV-2 infection of whom 83 were detected by the rapid antigen test (sensitivity 62.9%, 54.0% to 71.1%). In those who were still asymptomatic at the time of sampling, sensitivity was 58.7% (51.1% to 66.0%) for Veritor (n=2317) and 59.4% (49.2% to 69.1%) for Biosensor (n=1414), and in those who developed symptoms were 84.2% (68.7% to 94.0%; n=219) for Veritor and 73.3% (54.1% to 87.7%; n=158) for Biosensor. When a viral load cut-off was applied for infectiouness (≥5.2 log10 SARS-CoV-2 E gene copies/mL), the overall sensitivity was 90.1% (84.2% to 94.4%) for Veritor and 86.8% (78.1% to 93.0%) for Biosensor, and 88.1% (80.5% to 93.5%) for Veritor and 85.1% (74.3% to 92.6%) for Biosensor, among those who remained asymptomatic throughout. Specificities were >99%, and positive and negative predictive values were >90% and >95%, for both rapid antigen tests in all analyses. Conclusions The sensitivities of both rapid antigen tests in asymptomatic and presymptomatic close contacts tested on day 5 onwards after close contact with an index case were more than 60%, increasing to more than 85% after a viral load cut-off was applied as a proxy for infectiousness.

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