Platelet Count Rose While D-Dimer Levels Dropped as Deaths and Thrombosis Declined-An Observational Study on Anticoagulation Shift in COVID-19

Thromb Haemost. 2021 Dec;121(12):1610-1621. doi: 10.1055/a-1477-3829. Epub 2021 Apr 8.


Background: High levels of D-dimer and low platelet counts are associated with poor outcome in coronavirus disease 2019 (COVID-19). As anticoagulation appeared to improve survival, hospital-wide recommendations regarding higher doses of anticoagulation were implemented on April 9, 2020.

Objectives: To investigate if trends in D-dimer levels and platelet counts were associated with death, thrombosis, and the shift in anticoagulation.

Methods: Retrospective cohort study of 429 patients with COVID-19 at Karolinska University Hospital. Information on D-dimer levels and platelet counts was obtained from laboratory databases and clinical data from medical records.

Results: Thirty-day mortality and thrombosis rates were 19% and 18%, respectively. Pulmonary embolism was common, 65/83 (78%). Increased D-dimer levels in the first week in hospital were significantly associated with death and thrombosis (odds ratio [OR]: 6.06; 95% confidence interval [CL]: 2.10-17.5 and 3.11; 95% CI: 1.20-8.10, respectively). If platelet count increased more than 35 × 109/L per day, the mortality and thrombotic risk decreased (OR: 0.16; 95% CI: 0.06-0.41, and OR: 0.36; 95% CI: 0.17-0.80). After implementation of updated hospital-wide recommendations, the daily mean significantly decreased regarding D-dimer levels while platelet counts rose; -1.93; 95% CI: -1.00-2.87 mg/L FEU (fibrinogen-equivalent unit) and 65; 95% CI: 54-76 ×109/L, and significant risk reductions for death and thrombosis were observed; OR: 0.48; 95% CI: 0.25-0.92 and 0.35; 95% CI: 0.17-0.72.

Conclusion: In contrast to D-dimer levels, increase of platelet count over the first week in hospital was associated with improved survival and reduced thrombotic risk. The daily mean levels of D-dimer dropped while the platelet counts rose, coinciding with increased anticoagulation and a decline in thrombotic burden and mortality.

Publication types

  • Multicenter Study
  • Observational Study

MeSH terms

  • Administration, Oral
  • Aged
  • Anticoagulants / administration & dosage*
  • Anticoagulants / adverse effects
  • Biomarkers / blood
  • Blood Platelets / drug effects*
  • Blood Platelets / metabolism
  • COVID-19 / blood
  • COVID-19 / diagnosis
  • COVID-19 / mortality
  • COVID-19 Drug Treatment*
  • Female
  • Fibrin Fibrinogen Degradation Products / metabolism*
  • Hospital Mortality
  • Humans
  • Male
  • Middle Aged
  • Retrospective Studies
  • Sweden / epidemiology
  • Thrombosis / blood
  • Thrombosis / diagnosis
  • Thrombosis / drug therapy*
  • Thrombosis / mortality
  • Time Factors
  • Treatment Outcome


  • Anticoagulants
  • Biomarkers
  • Fibrin Fibrinogen Degradation Products
  • fibrin fragment D