Diagnostic accuracy of a SARS-CoV-2 rapid test and optimal time for seropositivity according to the onset of symptoms

Point-of-care serological tests for SARS-CoV-2 have been used for COVID-19 diagnosis. However, their accuracy over time regarding the onset of symptoms is not fully understood. We aimed to assess the accuracy of a point-of-care lateral flow immunoassay (LFI). Subjects, aged over 18 years, presenting clinical symptoms suggestive of acute SARS-CoV-2 infection were tested once by both nasopharyngeal and oropharyngeal RT-PCR and LFI. The accuracy of LFI was assessed in periodic intervals of three days in relation to the onset of symptoms. The optimal cut-off point was defined as the number of days required to achieve the best sensitivity and specificity. This cut-off point was also used to compare LFI accuracy according to participants’ status: outpatient or hospitalized. In total, 959 patients were included, 379 (39.52%) tested positive for SARS-CoV-2 with RT-PCR, and 272 (28.36%) tested positive with LFI. LFI best performance was achieved after 10 days of the onset of symptoms, with sensitivity and specificity of 84.9% (95%CI: 79.8-89.1) and 94.4% (95%CI: 91.0-96.8), respectively. Although the specificity was similar (94.6% vs. 88.9%, p = 0.051), the sensitivity was higher in hospitalized patients than in outpatients (91.7% vs. 82.1%, p = 0.032) after 10 days of the onset of symptoms. Best sensitivity of point-of-care LFI was found 10 days after the onset of symptoms which may limit its use in acute care. Specificity remained high regardless of the number of days since the onset of symptoms.

Bibliographic Details

Main Authors:	David,Caroline Nespolo de, Varela,Fernanda Hammes, Sartor,Ivaine Tais Sauthier, Polese-Bonatto,Márcia, Fernandes,Ingrid Rodrigues, Zavaglia,Gabriela Oliveira, Kern,Luciane Beatriz, Ferreira,Charles Francisco, Bastos,Gisele Alsina Nader, Pitrez,Paulo Márcio, Almeida,Walquiria Aparecida Ferreira de, Porto,Victor Bertollo Gomes, Zavascki,Alexandre Prehn, Stein,Renato Tetelbom, Scotta,Marcelo Comerlato
Format:	Digital revista
Language:	English
Published:	Escola Nacional de Saúde Pública Sergio Arouca, Fundação Oswaldo Cruz 2022
Online Access:	http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0102-311X2022000105007
Tags:	Add Tag No Tags, Be the first to tag this record!