# Droplet Digital PCR or Real-Time PCR as a Method for Quantifying SARS-CoV-2 RNA in Plasma—Is There a Difference?

## TL;DR

This study compares two PCR methods for detecting SARS-CoV-2 RNA in plasma and finds they provide similar results despite some discrepancies.

## Contribution

The study provides a direct comparison of qRT-PCR and RT-ddPCR for SARS-CoV-2 RNA detection in plasma, highlighting their comparable effectiveness.

## Key findings

- 89 out of 128 samples showed consistent results between qRT-PCR and RT-ddPCR.
- RT-ddPCR detected higher viral quantities but did not show superior sensitivity.
- Both methods are comparable for detecting SARS-CoV-2 E-gene RNA in plasma.

## Abstract

The aim of this study is to ascertain whether qRT-PCR (reverse transcriptase real-time PCR) or RT-ddPCR (reverse transcriptase digital droplet PCR) is more effective for detecting SARS-CoV-2 RNA (severe acute respiratory syndrome coronavirus 2 RNA) in blood plasma from COVID-19 (coronavirus infectious disease-19) patients. The E-gene of SARS-CoV-2 RNA was quantified using both methods in 128 plasma samples from 70 hospitalized patients, followed by a statistical analysis to compare the sensitivity and concordance between the methods. Out of the 128 samples, 89 yielded consistent results irrespective of the method used, whereas 39 samples showed discrepancies between the two different methods. RT-ddPCR frequently registered higher viral quantities compared to qRT-PCR; however, the results did not demonstrate a clear superiority in sensitivity for RT-ddPCR. Although RT-ddPCR registered higher viral quantities, this study concludes that both methods provide comparable results for detecting SARS-CoV-2 E-gene RNA in plasma.