Role of population and test characteristics in antigen-based SARS-CoV-2 diagnosis, Czechia, August to November 2021

Abstract

Background Analyses of diagnostic performance of SARS-CoV-2 antigen rapid diagnostic tests (AG-RDTs) based on long-term data, population subgroups and many AG-RDT types are scarce. Aim We aimed to analyse sensitivity and specificity of AG-RDTs for subgroups based on age, incidence, sample type, reason for test, symptoms, vaccination status and the AG-RDT’s presence on approved lists. Methods We included AG-RDT results registered in Czechia’s Information System for Infectious Diseases between August and November 2021. Subpopulations were analysed based on 346,000 test results for which a confirmatory PCR test was recorded ≤ 3 days after the AG-RDT; 38 AG-RDTs with more than 100 PCR-positive and 300 PCR-negative samples were individually evaluated. Results Average sensitivity and specificity were 72.4% and 96.7%, respectively. We recorded lower sensitivity for age groups 0–12 (65.5%) and 13–18 years (65.3%). The sensitivity level rose with increasing SARS-CoV-2 incidence from 66.0% to 76.7%. Nasopharyngeal samples had the highest sensitivity and saliva the lowest. Sensitivity for preventive reasons was 63.6% vs 86.1% when testing for suspected infection. Sensitivity was 84.8% when one or more symptoms were reported compared with 57.1% for no symptoms. Vaccination was associated with a 4.2% higher sensitivity. Significantly higher sensitivity levels pertained to AG-RDTs on the World Health Organization Emergency Use List (WHO EUL), European Union Common List and the list of the United Kingdom’s Department of Health and Social Care. Conclusion AG-RDTs from approved lists should be considered, especially in situations associated with lower viral load. Results are limited to SARS-CoV-2 delta variant.

Can variants, reinfection, symptoms and test types affect COVID-19 diagnostic performance? A large-scale retrospective study of AG-RDTs during circulation of Delta and Omicron variants, Czechia, December 2021 to February 2022

“…Out of all collected results, we first selected only those where the same person had taken AG-RDT and PCR on the same day. Note that as justified in prior work [6], taking both tests on the same day may be indicative of a higher viral load given how testing in Czechia was organised. In the study period, there were longer waiting times for PCR tests than for AG-RDTs, which could be done at a wider network of testing sites, including general practitioners.…”

“…Each sample was associated with the same set of indicators that were used for subgroup analyses in [6], where these indicators are described in detail: reasons for the test (indication), vaccination status, age group, region-level incidence and presence of at least one symptom.…”

“…The preventive reason was used mainly for tests of asymptomatic individuals at workplaces and for screening tests, the diagnostic reason for symptomatic patients and the epidemiological reason for contact tracing (refer to [6] for details). As in [6], a person was considered as vaccinated when at least 2 weeks after the first dose of the Janssen Ad26.COV2-S COVID-19 vaccine or 2 weeks after a second dose of any of the other vaccines approved in Czechia or vaccines approved abroad and recognised in Czechia. The age groups were 0-12 years, 13-18, 19-25, 26-59 and ≥ 60 years.…”

“…Our prior work [6] evaluated the EU list of COVID-19 antigen tests released on 6 May 2022 that contained a list of independently validated AG-RDTs. When the EU in vitro diagnostic medical device (IVD) regulation came into force, this list was split into the EU Category A list which requires that an AG-RDT is successfully evaluated by at least one prospective clinical field study and the EU Category B list which applies a less strict criterion of a retrospective in vitro study; both categories of studies also need to meet additional criteria [5].…”

The Impact of Vaccination on RT-PCR Cycle Threshold Values for COVID-19: Insights for Future Pandemic Preparedness

“…The global response to the pandemic varied signi cantly, in uenced by factors such as healthcare infrastructure, governmental measures, public compliance, and the emergence of different virus variants (Humer et al, 2023;Kliegr et al, 2023). In Africa, the response was diverse across countries, with initial forecasts predicting severe outbreaks due to limited health infrastructure and socio-economic challenges (Alhassan et al, 2023).…”