Influence of the characteristics of the nasopharyngeal exudate on PCR results for SARS-COV-2

Abstract

Introduction. The coronaviruses known as SARS-COV are the cause of severe acute respiratory syndrome. One of the diagnostic tests for coronavirus is the PCR test. The results that we can find after performing the PCR test are: Negative IgM, Positive IgM, indeterminate IgM or inhibited sample.
Objective. The main objective of this study was to assess whether the blood content or nasopharyngeal secretions in the PCR extraction inhibits the sample or causes an indeterminate SARS-CoV-2 result.
Methodology. This study retrospectively evaluates 213 samples taken from healthcare personnel who underwent a PCR test for SARS COV-2. Parameters such as blood content, nasopharyngeal secretions, difficulty in extraction and change of nostril during the PCR extraction were analyzed.
Results. 85,7% of the samples obtained an inhibited result and 78,9% an indeterminate result, when the extracted sample contained hematic content.
Conclusions. We conclude that a PCR extraction with hematic content can inhibit or indeterminate the result of a PCR for SARS-COV-2, however, the PCR extraction for SARS-COV-2 with nasopharyngeal secretions, as well as the difficulty in the extraction or the change of fossa during the same, neither inhibits nor causes an indeterminate result in the result of the sample.