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

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.

Accuracy of Roche SARS-CoV-2 Rapid Antigen Test in Nasopharyngeal Swab: Clinical Impression Matters

“…Moreover, the patients on oxygen therapy either nasal canular or mask were found to be less co-operative during nasopharyngeal swab procedure; this logistic point was important in emergency setting, and, it also highlighted the need for either repeating RAT or RT-PCR for confi rmation of diagnosis. Anosmia was the only presenting symptom in two cases in this category and their clinical course was late [31], supporting the previous facts; performance of RAT was aff ected by the dynamics of SARS-CoV-2 viral load in early pre-symptomatic and later stages of viral shedding [28]. According to [32], anosmia symptom was usually late;…”

“…Even in RT-PCR test, we could not rely 100% on its accuracy [27]. Thus, a negative RAT result did not rule out the presence of SARS-CoV-2 infection, and he should be treated with great caution, especially in asymptomatic individuals [28].…”

Interpreting SARS-CoV-2 Test Results

“…4,6 Using viral culture as criterion standard, small studies of antigen tests have reported sensitivity of approximately 90% and specificity greater than 98%. [4][5][6] Patient Outcome…”

Diagnostic accuracy of three prevailing rapid antigen tests for detection of SARS-CoV-2 infection in the general population: cross sectional study

“…Secondary outcomes were diagnostic accuracies using a viral load cut-off as a proxy of infectiousness (≥5.2 log10 SARS-CoV-2 E-gene copies/mL), which was the viral load cut-off above which 95% of people with a positive molecular test had a positive virus culture in a recent study by our group 6 , and diagnostic accuracies stratified by presence of symptoms at time of sampling (yes or no), COVID-19 vaccination status (vaccinated with at least one dose yes or no), having had a prior SARS-CoV-2 infection (yes or no), sex (female or male), age (≥16 to 40 or >40 to 65 or >65), and testing indication (symptoms and/or close contact without symptoms). In an additional analysis, we performed WGS to assess whether falsenegative Ag-RDT results could be linked to SARS-CoV-2 variants or specific mutations in the SARS-CoV-2 N-gene (supplementary material 2).…”