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. 2020 Aug:129:104473.
doi: 10.1016/j.jcv.2020.104473. Epub 2020 May 27.

Alltest rapid lateral flow immunoassays is reliable in diagnosing SARS-CoV-2 infection from 14 days after symptom onset: A prospective single-center study

Felipe Pérez-García  1 , Ramón Pérez-Tanoira  2 , Juan Romanyk  3 , Teresa Arroyo  4 , Peña Gómez-Herruz  5 , Juan Cuadros-González  6
Affiliations

Alltest rapid lateral flow immunoassays is reliable in diagnosing SARS-CoV-2 infection from 14 days after symptom onset: A prospective single-center study

Felipe Pérez-García et al. J Clin Virol. 2020 Aug.

Abstract

Objectives: SARS-CoV-2 infection diagnosis is challenging in patients from 2 to 3 weeks after the onset of symptoms, due to the low positivity rate of the PCR. Serologic tests could be complementary to PCR in these situations. The aim of our study was to analyze the diagnostic performance of one serologic rapid test in COVID-19 patients.

Methods: We evaluated a lateral flow immunoassay (AllTest COVID-19 IgG/IgM) which detects IgG and IgM antibodies. We validated the serologic test using serum samples from 100 negative patients (group 1) and 90 patients with COVID-19 confirmed by PCR (group 2). Then, we prospectively evaluated the test in 61 patients with clinical diagnosis of pneumonia of unknown etiology that were negative for SARS-CoV-2 by PCR (group 3).

Results: All 100 patients from group 1 were negative for the serologic test (specificity = 100 %). Regarding group 2 (PCR-positive), the median time from their symptom onset until testing was 17 days. For these 90 group-2 patients, the test was positive for either IgM or IgG in 58 (overall sensitivity = 64.4 %), and in patients tested 14 days or more after the onset of symptoms, the sensitivity was 88.0 %. Regarding the 61 group-3 patients, median time after symptom onset was also 17 days, and the test was positive in 54 (88.5 % positivity).

Conclusions: Our study shows that Alltest lateral flow immunoassay is reliable as a complement of PCR to diagnose SARS-CoV-2 infection after 14 days from the onset of symptoms and in patients with pneumonia and negative PCR for SARS-CoV-2.

Keywords: Alltest; COVID-19; Diagnosis; Lateral flow immunoassay; SARS-CoV-2; Serologic rapid test.

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Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no conflicts of interest.

Figures

Fig. 1
Fig. 1
Temporal evolution of the positivity rate for IgM and IgG antibodies in group 2 patients (PCR positive).
See this image and copyright information in PMC

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