CliniCon Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2023

Does the presence of heparin in nasopharyngeal swabs interfere with detection of SARS-CoV-2 by PCR? If so, can the effect be prevented through the addition of the heparinase I enzyme? (94544)

Kira Edwards 1 2 , Taylor Corocher 2 , Yvonne Hersusianto 2 3 , Donald Campbell 4 5 , Prahlad Ho 1 2 5 , Paul Monagle 6 7 8 9
  1. Northern Clinical pathology, Thrombosis, and Radiology (NECTAR) Research Group, Northern Health, Epping, VIC, Australia
  2. Northern Pathology Victoria, Northern Health, Epping, VIC, Australia
  3. Infectious Diseases, Northern Health, Epping, VIC, Australia
  4. Hospital without Walls, Northern Health, Epping, VIC, Australia
  5. Department of Medicine, University of Melbourne, Melbourne, VIC, Australia
  6. Department of Paediatrics, University of Melbourne, Melbourne, VIC, Australia
  7. Haematology Research, Murdoch Children's Research Insitute, Melbourne, VIC, Australia
  8. Clinical Haematology, Royal Children's Hospital, Parkville, VIC, Australia
  9. Kids Cancer Centre, Sydney Children's Hospital, Randwick, NSW, Australia

Heparin is being investigated as a SARS-CoV-2 preventative in the IntraNasal HEpaRin Trial (INHERIT). However, heparin may interfere with polymerase chain reaction (PCR), the current gold-standard for the detection of SARS-CoV-2 in nasopharyngeal swab samples. We aimed to investigate how heparin affected various SARS-CoV-2 RT-qPCR assays, and if such interference could be ameliorated through the addition of the heparinase I enzyme. In the context of the INHERIT trial, PCR inhibition must be reversed to ensure accurate reporting of SARS-CoV-2 test results.

To assess the effect of heparin, residual SARS-CoV-2 positive samples were spiked with heparin in concentrations ranging from 10 – 5000 IU/mL, and SARS-CoV-2 assays performed on the Hologic Panther, GeneXpert, LIAT, Seegene + StarMag, and Seegene + TANBead platforms. To assess the ability of heparinase I to reverse the interfering effect of heparin (10-250 IU/mL), the same method was used with the addition of heparinase I.

The presence of heparin caused interference, however the degree of interference differed between testing platforms. When comparing expected vs. actual results, the percent (%) concurrence rates were: Hologic Panther 100.0%, GeneXpert 40.0%, LIAT 60.4%, Seegene + StarMag 12.5%, and Seegene + TANBead 41.7%.

The addition of heparinase I reversed RT-qPCR inhibition on the Seegene + StarMag platform, with resulting CT (cycle threshold) values comparable to those of the sample only controls. In addition, heparinase I was able to almost completely reverse PCR inhibition caused by heparin across a variety of grouped CT values (<20, 20-30, 30-35). In single or double gene positives, borderline incomplete reversal meant that positive/negative decisions may differ.

Overall, these results give confidence that the use of intranasal heparin does not affect the accuracy of SARS-CoV-2 assays when performed on the Hologic Panther platform. In addition, we have identified that utilising the heparinase I enzyme is a valid method for overcoming heparin interference when utilising RT-qPCR platforms such as the Seegene StarMag.