Evaluation of a Rapid Antigen Test To Detect SARS-CoV-2 Infection and Identify Potentially Infectious Individuals

Abstract

The identification and isolation of highly infectious SARS-CoV-2-infected individuals is an important public health strategy. Rapid antigen detection tests (RADT) are promising candidates for large-scale screenings due to timely results and feasibility for on-site testing. Nonetheless, the diagnostic performance of RADT in detecting infectious individuals is yet to be fully determined. In this study, RT-qPCR and virus culture of RT-qPCR positive samples were used to evaluate and compare the performance of the Standard Q COVID-19 Ag Test in detecting SARS-CoV-2 infected and possibly infectious individuals. To this end, two combined oro- and nasopharyngeal swabs were collected at a routine SARS-CoV-2 diagnostic center. A total of 2,028 samples were tested and 118 virus cultures inoculated. SARS-CoV-2 infection was detected in 210 samples by RT-qPCR, representing a positive rate of 10.36%. The Standard Q COVID-19 Ag Test yielded a positive result in 92 (4.54%) samples resulting in an overall sensitivity and specificity of 42.86% and 99.89%. For adjusted Ct values <20 (n=14), <25 (n=57), and <30 (n=88) the RADT reached sensitivities of 100%, 98.25%, and 88.64%, respectively. All 29 culture positive samples were detected by RADT. While overall sensitivity was low, Standard Q COVID-19 RADT reliably detected patients with high RNA loads. Additionally, negative RADT results fully corresponded with the lack of viral cultivability in Vero E6 cells. These results indicate that RADT can be a valuable tool for the detection of individuals that are likely to transmit SARS-CoV-2. RADT testing could therefore guide public health testing strategies to combat the COVID-19 pandemic.

Mobile PCR-based surveillance for SARS-CoV-2 to reduce visiting restrictions in nursing homes during the COVID-19 pandemic: a pilot study

“…We added the following post hoc exploratory descriptive analyses: (1) Ct values in RT-PCR samples to compare sensitivity of SARS-CoV-2 PCR and POCT. A Ct value of 27 in RT-PCR was set as cut-off for secure detection by POCT as described before [ 14 ]. (2) Overall mortality, COVID-19-related mortality defined as death while infected with SARS-CoV-2, and excess mortality were assessed by comparing NH mortality data of the same period in the previous year.…”

Rapid Antigen Tests for Voluntary Screen Testing

“…Figure 5 shows the estimated range of Ct values at a viral load of 100,000 Copies/mL from 42 identified standard curves. [12][13][14]20,22,23,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] The median Ct value at this viral load was 25.82 (interquartile range 23.03 to 29.27), with 46% of Ct values below 25, and 83% below 30. [12][13][14]20,22,23,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] The median Ct value at this viral load was 25.82 (interquartile range 23.03 to 29.27).…”

“…Figure 5. Ct Values at a Viral Load of 100,000 Copies/mL Estimated From 42 Standard Curves Box and Whisker plot of Ct values at a viral load of 100,000 Copies/mL from 42 identified PCR standard curves reported in 23 original articles [12][13][14]20,22,23,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. The median Ct value at this viral load was 25.82 (interquartile range 23.03 to 29.27).…”

“…Figure 6. Cumulative Distribution of Viral Loads at a Ct Value of 30 as Estimated From 42 Standard Curves Cumulative distribution curve derived from 42 PCR standard curves reported in 23 original articles [12][13][14]20,22,23,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. At a Ct value of 30, the median viral load was 5,400 copies/mL, and an estimated 83% of assays reported viral loads below 100,000 copies/mL at this threshold.…”

A Novel Approach for Evaluating Antibodies Against SARS-CoV-2 Using Menstrual Blood Collected from Sanitary Napkins Before and after Vaccination and Evaluation of the Visual Napkin Score

“…Various medical tests have been conducted for coronavirus disease 2019 (COVID-19), which has been raging worldwide since the end of 2019. These tests include antigen tests 1 , reverse-transcriptase polymerase chain reaction (RT-PCR) tests 2 , and antibody tests 3 . The materials used are different for each test and include nasopharyngeal swabs, oropharyngeal swabs, saliva samples, and blood samples taken from the ngertips.…”