Sensitivity assessment of droplet digital PCR for SARS-CoV-2 detection

Int J Mol Med. 2020 Sep;46(3):957-964. doi: 10.3892/ijmm.2020.4673. Epub 2020 Jul 13.

Abstract

Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) is the gold standard method for the diagnosis of COVID‑19 infection. Due to pre‑analytical and technical limitations, samples with low viral load are often misdiagnosed as false‑negative samples. Therefore, it is important to evaluate other strategies able to overcome the limits of RT‑qPCR. Blinded swab samples from two individuals diagnosed positive and negative for COVID‑19 were analyzed by droplet digital PCR (ddPCR) and RT‑qPCR in order to assess the sensitivity of both methods. Intercalation chemistries and a World Health Organization (WHO)/Center for Disease Control and Prevention (CDC)‑approved probe for the SARS‑CoV‑2 N gene were used. SYBR‑Green RT‑qPCR is not able to diagnose as positive samples with low viral load, while, TaqMan Probe RT‑qPCR gave positive signals at very late Ct values. On the contrary, ddPCR showed higher sensitivity rate compared to RT‑qPCR and both EvaGreen and probe ddPCR were able to recognize the sample with low viral load as positive even at 10‑fold diluted concentration. In conclusion, ddPCR shows higher sensitivity and specificity compared to RT‑qPCR for the diagnosis of COVID‑19 infection in false‑negative samples with low viral load. Therefore, ddPCR is strongly recommended in clinical practice for the diagnosis of COVID‑19 and the follow‑up of positive patients until complete remission.

MeSH terms

  • Betacoronavirus / genetics*
  • COVID-19
  • Coronavirus Infections / diagnosis*
  • Coronavirus Nucleocapsid Proteins
  • Humans
  • Nucleocapsid Proteins / genetics
  • Pandemics
  • Phosphoproteins
  • Pneumonia, Viral / diagnosis*
  • Polyproteins
  • RNA, Viral / analysis*
  • Real-Time Polymerase Chain Reaction / methods*
  • Reverse Transcriptase Polymerase Chain Reaction / methods*
  • SARS-CoV-2
  • Sensitivity and Specificity
  • Spike Glycoprotein, Coronavirus / genetics
  • Viral Proteins / genetics

Substances

  • Coronavirus Nucleocapsid Proteins
  • Nucleocapsid Proteins
  • ORF1ab polyprotein, SARS-CoV-2
  • Phosphoproteins
  • Polyproteins
  • RNA, Viral
  • Spike Glycoprotein, Coronavirus
  • Viral Proteins
  • nucleocapsid phosphoprotein, SARS-CoV-2
  • spike glycoprotein, SARS-CoV