We use cookies to understand how you use our site and to improve your experience. This includes personalizing content and advertising. To learn more, click here. By continuing to use our site, you accept our use of cookies. Cookie Policy.

Features Partner Sites Information LinkXpress
Sign In
Advertise with Us
Technopath Clinical Diagnostics - An LGC Company


  Silver Provides full range of instrumentation, reagent kits, software and quality control systems to clinical laboratories. ... read more Featured Products: More products

Download Mobile App


ATTENTION: Due to the COVID-19 PANDEMIC, many events are being rescheduled for a later date, converted into virtual venues, or altogether cancelled. Please check with the event organizer or website prior to planning for any forthcoming event.

SARS-Cov-2 RNA Detected in FFPE Tissue by Droplet Digital PCR

By LabMedica International staff writers
Posted on 22 Jun 2022
Print article
Image: SARS-CoV-2 ddPCR Kit is a partition-based endpoint RT-PCR test for the qualitative detection of nucleic acids from SARS-CoV-2 (Photo courtesy of Thermo Fisher Scientific)
Image: SARS-CoV-2 ddPCR Kit is a partition-based endpoint RT-PCR test for the qualitative detection of nucleic acids from SARS-CoV-2 (Photo courtesy of Thermo Fisher Scientific)

SARS-CoV-2 infection can result in diverse, multiorgan pathology, the most significant being in the lungs, heart, kidney, central nervous system, liver, lymph nodes, bone marrow, vasculature, intestine, and placenta.

SARS-CoV-2 infection is usually identified by the detection of viral RNA using reverse transcriptase polymerase chain reaction (RT-qPCR) on nasopharyngeal or oropharyngeal swabs. Patients with current or previous SARS-CoV-2 infection who present with “unexplained” acute or acute on chronic respiratory failure or other organ-specific manifestations may undergo tissue biopsy.

A team of diagnosticians from the Mayo Clinic (Rochester, MN, USA) developed and validated using droplet digital PCR (ddPCR a qualitative test for detection of SARS-CoV-2 in formalin-fixed paraffin-embedded (FFPE) tissues. Thirty-seven tissue samples from 35 autopsy cases (20 positive, 15 negative), a cell block from a cell line infected with SARS-CoV-2, and a cell block from a cell line infected with influenza virus were utilized in a study for accuracy, precision, stability, linearity, and specificity studies.

Total RNA, including viral RNA, was extracted from unstained FFPE tissue scrolls cut at 10 µm by either RNeasy DSP FFPE Kit or miRNeasy FFPE Kit (Qiagen, Hilden, Germany). The RNA was quantified, ranging from 12 to 800 ng/μL, and stored at −80 °C. The assay was performed using the Bio-Rad SARS-CoV-2 ddPCR Test (Bio-Rad Laboratories, Hercules, CA, USA). RNA samples were run both neat and at a 1:100 dilution. After the reaction was partitioned into droplets using the Bio-Rad AutoDG instrument, SARS-CoV-2 nucleocapsid (N1 and N2) target sequences, along with human ribonuclease P/MRP subunit 30 (RPP30) target as a control, were amplified using the Applied Biosystems’ Veriti thermocyclers (Thermo Fisher Scientific, Inc., Waltham, MA, USA).

The scientists reported that SARS-CoV-2 was detected in all 21 known positive samples and none of the 16 negative samples. As few as approximately five viral copies were reliably detected. Since January 2021, many tissue types have been clinically tested. Of the 195 clinical specimens, the positivity rate was 35% with placenta and fetal tissue showing the highest percentage of positive cases. Both intra- and inter-assay measurements were 100% concordant in qualitative positive or negative calls among all replicates for each sample. No amplification of either of the nucleocapsid targets was detected (i.e., 0 droplet count for both N1 and N2) for any of the non-SARS-CoV-2 viruses tested.

The authors concluded that that ddPCR provides both accuracy and sensitivity in detecting patients with low viral load. SARS-CoV-2 ddPCR testing will also aid in understanding atypical presentations of COVID-19, including in patients who present with “unexplained” symptoms or potential long-term sequelae. The study was published on June 15, 2022 in the journal Clinica Chimica Acta.

Related Links:
Mayo Clinic 
Bio-Rad Laboratories 
Thermo Fisher Scientific 

Gold Supplier
SARS-CoV-2 Antigen Rapid Test
RapiSafe SARS-CoV-2 Antigen Rapid Test (Professional use)
RT-PCR Enzymes and Kits
QuantiNova Pathogen +IC Kit
Automated Hematology Workstation
Influenza A+B Test
Anyplex FluA/B Typing Real-Time Detection

Print article
IIR Middle East



view channel
Image: OneDraw Blood Collection Device significantly reduces obstacles for drawing blood (Photo courtesy of Drawbridge Health)

Near Pain-Free Blood Collection Technology Enables High-Quality Testing

Blood tests help doctors diagnose diseases and conditions such as cancer, diabetes, anemia, and coronary heart disease, as well as evaluate organ functionality. They can also be used to identify disease... Read more


view channel
Image: The global infectious disease IVD market is expected to hit USD 57 billion by 2030 (Photo courtesy of Pexels)

Global Infectious Disease IVD Market Dominated by Molecular Diagnostics Technology

The global infectious disease in vitro diagnostics (IVD) market stood at USD 113.7 billion in 2021 and is expected to grow at a CAGR of -7.41% from 2022 to 2030 to hit around USD 56.89 billion by 2030,... Read more
Copyright © 2000-2022 Globetech Media. All rights reserved.