Background: Venous thromboembolism (VTE) is common among patients with severe coronavirus disease 2019 (COVID-19). Anticoagulation in hospitalized COVID-19 patients has been associated with survival benefit; however, the optimal thromboprophylaxis strategy has not yet been defined. Objective: To identify published guidance reports by national and international societies regarding thromboprophylaxis strategies in COVID-19 patients in different settings (outpatients, hospitalized, post-discharge). Methods: A systematic review of the literature (Pubmed/EMBASE) was conducted independently by two investigators. Results: Among 1942 initially identified articles, 33 guidance documents were included: 20 published by national and 13 by international societies. These documents provide recommendations mainly for hospitalized (97% of reports) and post-discharge (75%) COVID-19 patients, and less so for outpatients (34%). Thrombotic and bleeding risk stratification prior to any treatment decision is the cornerstone of all suggested thromboprophylaxis strategies; 81% of the documents recommend thromboprophylaxis for all hospitalized patients with a prophylactic dosage of low molecular weight heparin irrespective of VTE risk. Intermediate or therapeutic dose intensity is recommended in high VTE risk patients by 56% and 28% of documents, respectively. Mechanical thromboprophylaxis is suggested in case of high bleeding risk or contraindication to pharmacological thromboprophylaxis (59% of documents). Extended pharmacological thromboprophylaxis is recommended for patients with high VTE risk after hospital discharge (63% of documents). For non-hospitalized outpatients, 28% of documents recommend pharmacological thromboprophylaxis for high VTE risk. Conclusion: The current guidance identifies thromboprophylaxis in COVID-19 patients, especially during hospitalization, as of major importance for the prevention of VTE. Recommendations are derived from limited evidence from observational studies.

The role of immunomodulatory agents in the treatment of hospitalized patients with COVID-19 has been of increasing interest. Anakinra, an interleukin-1 inhibitor, has been shown to offer significant clinical benefits in patients with COVID-19 and hyperinflammation. An updated systematic review and meta-analysis regarding the impact of anakinra on the outcomes of hospitalized patients with COVID-19 was conducted. Studies, randomized or non-randomized with adjustment for confounders, reporting on the adjusted risk of death in patients treated with anakinra versus those not treated with anakinra were deemed eligible. A search was performed in PubMed/EMBASE databases, as well as in relevant websites, until 1 August 2021. The meta-analysis of six studies that fulfilled the inclusion criteria (n = 1553 patients with moderate to severe pneumonia, weighted age 64 years, men 66%, treated with anakinra 50%, intubated 3%) showed a pooled hazard ratio for death in patients treated with anakinra at 0.47 (95% confidence intervals 0.34, 0.65). A meta-regression analysis did not reveal any significant associations between the mean age, percentage of males, mean baseline C-reactive protein levels, mean time of administration since symptoms onset among the included studies and the hazard ratios for death. All studies were considered as low risk of bias. The current evidence, although derived mainly from observational studies, supports a beneficial role of anakinra in the treatment of selected patients with COVID-19.

Coronavirus disease 2019 (COVID-19) has been shown to be strongly associated with increased risk for venous thromboembolism events (VTE) mainly in the inpatient but also in the outpatient setting. Pharmacologic thromboprophylaxis has been shown to offer significant benefits in terms of reducing not only VTE events but also mortality, especially in acutely ill patients with COVID-19. Although the main source of evidence is derived from observational studies with several limitations, thromboprophylaxis is currently recommended for all hospitalized patients with acceptable bleeding risk by all national and international guidelines. Recently, high quality data from randomized controlled trials (RCTs) further support the role of thromboprophylaxis and provide insights into the optimal thromboprophylaxis strategy. The aim of this statement is to systematically review all the available evidence derived from RCTs regarding thromboprophylaxis strategies in patients with COVID-19 in different settings (either inpatient or outpatient) and provide evidence-based guidance to practical questions in everyday clinical practice. Clinical questions accompanied by practical recommendations are provided based on data derived from 20 RCTs that were identified and included in the present study. Overall, the main conclusions are: (i) thromboprophylaxis should be administered in all hospitalized patients with COVID-19, (ii) an optimal dose of inpatient thromboprophylaxis is dependent upon the severity of COVID-19, (iii) thromboprophylaxis should be administered on an individualized basis in post-discharge patients with COVID-19 with high thrombotic risk, and (iv) thromboprophylaxis should not be routinely administered in outpatients. Changes regarding the dominant SARS-CoV-2 variants, the wide immunization status (increasing rates of vaccination and reinfections), and the availability of antiviral therapies and monoclonal antibodies might affect the characteristics of patients with COVID-19; thus, future studies will inform us about the thrombotic risk and the optimal therapeutic strategies for these patients.

Thromboprophylaxis in hospitalized patients with COVID-19 has been associated with a survival benefit and is strongly recommended. However, the optimal dose of thromboprophylaxis remains unclear. A systematic review and meta-analysis (PubMed/EMBASE) of studies comparing high (intermediate or therapeutic dose) versus standard (prophylactic dose) intensity of thrombo-prophylaxis with regard to outcome of hospitalized patients with COVID-19 was performed. Randomized and non-randomized studies that provided adjusted effect size estimates were included. Meta-analysis of 7 studies comparing intermediate versus prophylactic dose of thromboprophylaxis (2 randomized and 5 observational, n = 2009, weighted age 61 years, males 61%, ICU 53%) revealed a pooled adjusted relative risk (RR) for death at 0.56 (95% confidence intervals (CI) 0.34, 0.92) in favor of the intermediate dose. For the same comparison arms, the pooled RR for venous thromboembolism was 0.84 (95% CI 0.54, 1.31), and for major bleeding events was 1.63 (95% CI 0.79, 3.37). Meta-analysis of 17 studies comparing therapeutic versus prophylactic dose of thromboprophylaxis (2 randomized and 15 observational, n = 7776, weighted age 64 years, males 54%, ICU 21%) revealed a pooled adjusted RR for death at 0.73 (95% CI 0.47, 1.14) for the therapeutic dose. An opposite trend was observed in the unadjusted analysis of 15 observational studies (RR 1.24 (95% CI 0.88, 1.74)). For the same comparison arms, the pooled RR for venous thromboembolism was 1.13 (95% CI 0.52, 2.48), and for major bleeding events 3.32 (95% CI 2.51, 4.40). In conclusion, intermediate compared with standard prophylactic dose of thromboprophylaxis appears to be rather safe and is associated with additional survival benefit, although most data are derived from observational retrospective analyses. Randomized studies are needed to define the optimal thromboprophylaxis in hospitalized patients with COVID-19.