Interpretation of single target positivity among SARS-CoV-2 RT-PCR result tests

https://doi.org/10.1016/j.jcvp.2021.100021Get rights and content
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Highlights

  • Diagnosis of SARS-CoV-2 is based on amplification and detection of several viral genes.

  • In some SARS-CoV-2 RT-PCR tests, only one target gene is detected and interpretation is unclear.

  • Among 264 patients with one target positive results, 68% were classified as probable COVID-19.

Abstract

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) recently emerged and is responsible for coronavirus disease 19 (COVID-19). Diagnostic tests have been developed, mainly based on reverse-transcriptase PCR (RT-PCR). Most RT-PCR assays target at least two SARS-CoV-2 genes. In some cases, only one target gene is detected; the interpretation of such cases remains unclear.

Objectives

Our objective was to analyse one target positive (OPT) RT-PCR results, using two RT-PCR assays: the Xpert® Xpress SARS-CoV-2 (Cepheid diagnosis, “Cepheid”) and the Cobas® 6800 SARS-CoV-2 Test (Roche Molecular Diagnostics, “Roche”).

Methods

All SARS-CoV-2 RT-PCR results performed on respiratory samples with the Roche or the Cepheid tests, from 23rd March to 6th August 2020 were collected. A patient with an OPT result was classified as “probable COVID-19” if they met at least one of the three following criteria: (i) history of a two gene-positive SARS-CoV-2 RT-PCR result, (ii) anti-SARS-CoV-2 antibody (IgG) detection or (iii) compatible chest computed tomography scan (CT-scan).

Results

A total of 18,630 and 1189 SARS-CoV-2 RT-PCR tests were performed with the Roche and Cepheid tests, respectively. Among the positive SARS-CoV-2 RT-PCR, 293 samples – corresponding to 264 patients – were OPT (11% of the positive samples). Of these patients, 180 (68%) had at least one of the three criteria listed above and were classified as probable COVID-19.

Conclusions

Sixty-eight percent of the patients with an OPT result were classified as probable COVID-19 and are probably at a late stage of infection. Serology and imaging can be helpful to confirm diagnosis.

Keywords

SARS-CoV-2
COVID-19
Molecular biology
One target positive RT-PCR result

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1

These authors contributed equally to this work.