Anti-SARS-Cov-2 IgA in Current Scenario of IgM and IgG Rapid Test: a New Alternative for the Diagnostic of COVID-19
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COVID-19
Anti-SARS-Cov-2 IgA in Current Scenario of IgM and IgG Rapid Test: a New Alternative for the Diagnostic of COVID-19 Christian La Rosa Fabián 1,2
&
Leticia Urquizo Briceño 3
Accepted: 24 September 2020 # Springer Nature Switzerland AG 2020
To the editor, Currently, we are facing SARS-CoV-2; the gold standard for the COVID-19 diagnosis is through nucleic acid analysis, that is, the demonstration of SARS-CoV-2 RNA in respiratory samples. Within the contribution of laboratory tests are serological tests, which are still an integral part of the general response and can complement the diagnosis based on the real-time reverse transcription polymerase chain reaction (RT-PCR) test, by confirming the antibody response during the early stage of infection [1]. The traditional scheme of specific IgM and IgG detection for SARS-CoV-2 allows classifying the temporary state of the infection; although the dynamics of the immune response in COVID-19 is not fully understood, typically IgM antibodies are produced by immune cells of the host during the early stages of a viral infection [2]. However, the mucosal and systemic IgA responses that may play a critical role in the pathogenesis of the disease have received much less attention. The detection of these antibodies can be performed by a wide variety of methods; there are four main types of methods for serological diagnosis: lateral flow immunochromatographic assay (LFIA), enzyme-linked immunosorbent assay (ELISA), chemiluminescent immunoassay (CLIA), and the neutralization assay [3]. Among the advantages of LFIA, also called “rapid test,” we have that is easy to use, with a time to obtain results between 10 and 30 min; in addition to the shortage of molecular This article is part of the Topical Collection on Covid-19 * Christian La Rosa Fabián [email protected] 1
Department of Clinical Pathology, Hospital Nacional dos de Mayo, Lima, Peru
2
Faculty of Medicine, Universidad Nacional Mayor de San Marcos, Lima, Peru
3
Resident of Clinical Pathology, Universidad Nacional Mayor de San Marcos, Lima, Peru
tests, it has been the technique chosen within the workflow for countries with limited resources [4]. Generally, rapid tests has a poor diagnostic performance compared with ELISA tests, which can be explain not only by the known technical differences between the two methodologies but also for the possible low concentrations of antibodies that can contribute even more to false negatives or false positives because of a non-specific binding observed with LFIA method. A lot of researches demonstrate the great variability in the performance of LFIA; given this, it seems that other methodologies such ELISA and CLIA have shown a better performance [5]. Yu et al. detected the IgA seroconversion on day 2 and IgM/IgG on day 5 after the symptoms onset. Furthermore, the study reported that 100% of the cases had detectable levels of IgA, IgG, and IgM on day 32 after the symptoms onset [6]. It seems that the IgM detection despite being performed by other methodologies different
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