ArticleThe Brazilian journal of infectious diseases : an official publication of the Brazilian Society of Infectious Diseases
Time-dependent decay of detectable antibodies against SARS-CoV-2: A comparison of ELISA with two batches of a lateral-flow test.
Article in The Brazilian journal of infectious diseases : an official publication of the Brazilian Society of Infectious Diseases. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 6 papers, 1 of them a synthesis that pooled it.
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6 citing papers in PubMed, 1 synthesis or guideline pooled it.
- Dynamics of SARS-CoV-2 seroassay sensitivity: a systematic review and modelling study.Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin · 2023Pooled it
- From a recombinant key antigen to an accurate, affordable serological test: Lessons learnt from COVID-19 for future pandemics.Biochemical engineering journal · 2022Article
- Chronic non-communicable diseases and COVID-19: EPICOVID-19 Brazil results.Revista de saude publica · 2021Article
- COVID-19 and social distancing among children and adolescents in Brazil.Revista de saude publica · 2021Article
- Prevalence of symptoms of COVID-19 in the state of Rio Grande do Sul: results of a population-based study with 18,000 participants.Revista de saude publica · 2021Article
- Population-level seropositivity trend for SARS-Cov-2 in Rio Grande do Sul, Brazil.Revista de saude publica · 2021Article
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17 authors.
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Abstract
backgroundLarge-scale epidemiological studies of seroprevalence of antibodies against SARS-CoV-2 often rely on point-of-care tests that provide immediate results to participants. Yet, little is known on how long rapid tests remain positive after the COVID-19 episode, or how much variability exists across different brands and even among batches of the same test.
methodsIn November 2020, we assessed the sensitivity of three tests applied to 133 individuals with a previous positive PCR result between April and October. All subjects provided finger prick blood samples for two batches (A and B) of the Wondfo lateral-flow IgG/IgM test, and dried blood spot samples for the S-UFRJ ELISA test.
resultsOverall sensitivity levels were 92.5% (95% CI 86.6-96.3), 63.2% (95% CI 54.4-71.4) and 33.8% (95% CI 25.9-42.5) for the S-UFRJ test, Wondfo A and Wondfo B tests, respectively. There was no evidence of a decline in the positivity of S-UFRJ with time since the diagnosis, but the two Wondfo batches showed sharp reductions to as low as 41.9% and 19.4%, respectively, for subjects with a positive PCR in June or earlier. Positive results for batch B of the rapid test were 35% to 54% lower than for batch A at any given month of diagnosis.
interpretationWhereas the ELISA test showed high sensitivity and stability of results over the five months of the study, both batches of the rapid test showed substantial declines, with one of the batches consistently showing lower sensitivity levels than the other. ELISA tests based on dried-blood spots are an inexpensive alternative to rapid lateral-flow tests in large-scale epidemiological studies.
fundingThe study was funded by the "Todos Pela Saúde" initiative, Instituto Serrapilheira, Brazilian Ministry of Health, Brazilian Collective Health Association (ABRASCO) and the JBS S.A. initiative 'Fazer o Bem Faz Bem'.
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