Incidence of deep vein thrombosis among non‐ICU patients hospitalized for COVID‐19 despite pharmacological thromboprophylaxis: Response from original authors Pola et al

Dear Editor,

We thank Dr Thachil for his interesting comment regarding our article.¹ Indeed, we agree that the precise contribution of various risk factors to the development of venous thromboembolism (VTE) in COVID‐19 patients remains to be fully elucidated. In this context, it is possible that hypoxia, either prior or during hospitalization, might also have a role in the development of thrombosis. In our study, non–intensive care unit subjects with deep vein thrombosis (DVT) more frequently required oxygen supplementation (100.0% versus 83.7%) and high‐flow nasal oxygen therapy or non‐invasive ventilation (NIV; 60.0% versus 8.1%) compared to those who had no DVT.² Based on the considerations of Dr Thachil, we have reanalyzed the dataset of our study, finding that the need for oxygen supplementation at the moment of the admission to the hospital also was relatively more frequent among those subjects who were subsequently found to have DVT, compared to those who were not (70.0% versus 42.2%). However, it is also likely that the general clinical conditions of the patients that had severe respiratory insufficiency were more critical than those of the other patients, or that their immobilization lasted for a longer period of time, or that additional unappreciated concomitant factors were present, and this makes it difficult to determine whether hypoxia per se was an independent and clinically relevant risk factor for thrombosis. We believe that this issue deserves further investigation and that future studies on thrombosis in COVID‐19 patients should be designed to assess the independent contribution of hypoxia to the development of thrombosis.

CONFLICTS OF INTEREST

The authors of this article (Angelo Porfidia, Angelo Santoliquido, Giulia Cammá, Enrica Porceddu and Roberto Pola) have no conflicts of interest to disclose.