Combination of rRT-PCR and Anti-Nucleocapsid/Anti-Spike Antibodies to Characterize Specimens with Very Low Viral SARs-CoV-2 Load: A Real-Life Experience.

Zoe Florou,Georgia Papadamou,Efthymia Petinaki,Aikaterini Belia,Meropi Zigra,George C Fthenakis,Katerina Tsilipounidaki,Philippos Kartalidis

doi:10.3390/microorganisms9061263

Zoe Florou, Georgia Papadamou + Show 6 more

Open Access

https://doi.org/10.3390/microorganisms9061263

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Abstract

The objective of the present study was to evaluate the true positivity among people, whose results of initial testing of nasopharyngeal swabs (NPS) showed a very low viral load of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Seventy-seven people detected with low viral loads of SARs-CoV-2 in nasopharyngeal samples (Ct ≥ 35) were enrolled in the study. For this purpose, a second NPS was collected for rRT-PCR (real-time reverse transcription polymerase chain reaction) combined with a pair of serum samples for detection of anti-nucleocapsid (anti-N) and anti-spike (anti-S) antibodies. In 8 people, subsequent examinations indicated an increase in viral loads, thereafter, followed by an increase of anti-N and anti-S antibodies, findings compatible with an early stage of COVID-19 infection. In 9 people, who already had increased anti-N antibodies, subsequent examination showed a decrease or absence of viral load and an increase in antibodies, indicative of a late stage of COVID-19 infection. In 60 people, subsequent examination showed absence of infection (as indicated by absence of viral load and antibodies). We propose that the combination of a second NPS and one serum-specimen, both taken three days after the first NPS, helps significantly to avoid false-positive results.

Highlights

SARS-CoV-2 is a novel coronavirus that has emerged in the last year, leading to a worldwide pandemic of COVID-19 disease, that has affected over 219 countries [1,2]
The objective of the present study was to evaluate the true positivity among people whose results of initial testing of nasopharyngeal swabs showed a very low viral load of SARS-CoV-2
Total Number of Samples Processed for Diagnosis of SARS-CoV-2 Infection

Summary

Introduction

SARS-CoV-2 is a novel coronavirus that has emerged in the last year, leading to a worldwide pandemic of COVID-19 disease, that has affected over 219 countries [1,2]. In order to control this new pathogen, the development of novel diagnostics and antiviral therapies is being considered the highest priority. Whole genome sequencing of SARSCoV-2 led scientists to apply novel molecular approaches in virus-detection and drugdevelopment. During the early period of the pandemic, complete sequencing of SARSCoV-2 facilitated the specific primer-designing and laboratory diagnosis of COVID-19 [3]. Current studies are focused on comprehensive characterization of the structure of the spike protein as a crucial step to find new therapeutics, which will interrupt the process of recognition and the entry of virus into the cell [5]

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