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July, 2020 Quick Question on Covid Coag Results

Our July, 2020 Quick Question, “What assay does your lab use to monitor Covid-19 severity?” attracted 64 responses that were nearly unanimous.


  1. Fibrin degradation products: 3 [5%]
  2. D-dimer: 53 [83%]
  3. PT and PTT: 3 [5%]
  4. Platelet count: 1 [2%]
  5. Other: 4 [6%]

Several publications, especially from China, record the parallel use of FDPs and D-dimers, which seems redundant. Most North American laboratories have dropped the semiquantitative FDP for the quantitative D-dimer, though FDP remains a useful assay in underresourced or “field” locations. Though the PT, PTT, and platelet count results tend to reflect advanced state Covid-related coagulopathy, their results are inconsistent.

In relation to the “Other” response, please click on our Covid Labs Table entry, posted July 25, 2020. Further, a July 26 ASCLS webinar illustrated the rapid and marked response of procalcitonin and interleukin-6 levels reflecting the “cytokine storm” phase of the Covid infection and supports these as useful clinical tools. Because Covid has triggered an increase of D-dimer orders and a snowstorm of publications, the time-honored problem of D-dimer unit reporting has again risen. We’ve partially addressed this in the Covid Labs Table, and the issue is expanded upon in Favaloro EJ, Thachil J. Reporting of D-dimer data in COVID-19: some confusion and potential for misinformation. Clin Chem Lab Med 2020; 58: 1191–9. The Favaloro article points out that D-dimer units are undefined in many research reports, leading to confusion and even disinformation.

The results of various hemostasis assays raise questions about the pathophysiology of advanced Covid symptoms. George has invited Andrew Goodwin, MD, CLIA Medical Director, University of Vermont Medical Center (UVMMC), Laboratory Services and Section Medical Director, Thrombosis and Hemostasis Laboratory, to provide a Q&A webinar, Covid-Associated Coagulopathy: A Conversation about the Controversies and Confusion on Tuesday, September 15, 2020, 4–5 CDT. George and Dr. Goodwin will explore the multiple theories of hemostasis pathology in Covid, detailing the laboratory assay results that support each hypothesis. Please save the date and watch Fritsma Factor for login details.

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