LAUSR

We thank the authors for their very useful and constructive criticisms about laboratory monitoring of haemostatic variables detailed in the ISTH guidance document for coagulopathy in COVID-19. We still believe that the use of simple and easily available laboratory markers both at admission and whilst in the hospital is necessary in the management of COVID-19 patients. Since the writing of this guidance and the letter from the experts being sent to us, there have been several reports of very high incidence of both arterial and venous thromboembolism (TE) in patients with COVID-19.1,2,3 In one report published in the Journal of Thrombosis and Haemostasis, the incidence of venous TE was 25%, some of whom died from this complication.2 Laboratory markers including D-dimer were relevant in these patients. The authors used D-dimer cut-off of 1.5 µg/mL for predicting venous TE and demonstrated sensitivity of 85.0% and specificity of 88.5% and negative predictive value of 94.7%.2 They also suggested D-dimers may be used to monitor the effectiveness of anticoagulants although this practice is not universally accepted.