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
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Author
Kliegr, Tomáš
Jarkovský, Jiří
Jiřincová, Helena
Kuchař, Jaroslav
Karel, Tomáš
Chudán, David
Vojíř, Stanislav
Zavřel, Michal
Šanca, Ondřej
Publication date
2023Published in
EurosurveillanceVolume / Issue
28 (38)ISBN / ISSN
ISSN: 1025-496XISBN / ISSN
eISSN: 1560-7917Metadata
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This publication has a published version with DOI 10.2807/1560-7917.ES.2023.28.38.2200938
Abstract
Background: The sensitivity and specificity of selected antigen detection rapid diagnostic tests (AG-RDTs) for SARS-CoV-2 were determined in the unvaccinated population when the Delta variant was circulating. Viral loads, dynamics, symptoms and tissue tropism differ between Omicron and Delta.Aim: We aimed to compare AG-RDT sensitivity and specificity in selected subgroups during Omicron vs Delta circulation.Methods: We retrospectively paired AG-RDT results with PCRs registered in Czechia's Information System for Infectious Diseases from 1 to 25 December 2021 (Delta, n = 20,121) and 20 January to 24 February 2022 (Omicron, n = 47,104).Results: When confirmatory PCR was conducted on the same day as AG-RDT as a proxy for antigen testing close to peak viral load, the average sensitivity for Delta was 80.4% and for Omicron 81.4% (p < 0.05). Sensitivity in vaccinated individuals was lower for Omicron (OR = 0.94; 95% confidence interval (CI): 0.87-1.03), particularly in reinfections (OR = 0.83; 95% CI: 0.75-0.92). Saliva AG-RDT sensitivity was below average for both Delta (74.4%) and Omicron (78.4%). Tests on the European Union Category A list had higher sensitivity than tests in Category B. The highest sensitivity for Omicron (88.5%) was recorded for patients with loss of smell or taste, however, these symptoms were almost 10-fold less common than for Delta. The sensitivity of AG-RDTs performed on initially asymptomatic individuals done 1, 2 or 3 days before a positive PCR test was consistently lower for Omicron compared with Delta.Conclusion: Sensitivity for Omicron was lower in subgroups that may become more common if SARS-CoV-2 becomes an endemic virus.
Keywords
AG-RDTs, SARS-CoV-2, Delta, Omicron, PCR
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https://hdl.handle.net/20.500.14178/2036License
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