Efficacy and safety of intensified versus standard prophylactic anticoagulation therapy in patients with Covid-19: a systematic review and meta-analysis

Clinical and economic implications of false-positive heparin-induced thrombocytopenia immunoassays: utility of the 4T score

Heparin-induced thrombocytopenia (HIT) is a prothrombotic condition induced by platelet-activating IgG antibodies that recognize PF4/heparin complexes. Diagnosis of HIT relies on enzyme immunologic assays (EIAs) and functional assays [serotonin release assay (SRA)]. Our institution uses a latex immunoturbidimetric assay (LIA), which has shown a positive-predictive value (PPV) of 55.6%, and a negative-predictive value (NPV) of 99.7%. The low PPV of EIAs/LIAs, in combination with the clinical delay in obtaining results of a SRA, commonly leads to a false-positive diagnosis of HIT and inappropriate treatment. We performed a single-institution retrospective study at a large tertiary center to assess patient management decisions and economic costs following a false-positive HIT (LIA) test. This study found an 89.5% incidence of false-positive HIT (LIA) tests. 97.4% of patients underwent anticoagulation changes. 69.6% of patients were switched to argatroban. Of patients with a false-positive HIT immunoassay (LIA), 42 (40.7%) patients were on a prophylactic dose of anticoagulation at the time of HIT (LIA) positivity, of which 22 (52.4%) were switched to full anticoagulation with either argatroban or fondaparinux. Of the 22 patients switched to full anticoagulation, 15 (68%) had low-probability 4T scores. Seven (8.8%) of patients had bleeding events after HIT (LIA) positivity. All seven patients were switched to argatroban from a full-dose heparin anticoagulation. Five of the seven patients were considered major bleeds. Utilization of argatroban incurred substantial costs, estimated at approximately $73 000 for false-positive HIT cases. False-positive HIT (LIA) tests contribute to unwarranted anticoagulation changes, increased bleeding risks, and substantial healthcare costs. Incorporating the 4T score into diagnostic algorithms may help mitigate these risks by guiding appropriate clinical decisions. Future research should focus on refining diagnostic approaches and standardizing management strategies to improve patient outcomes and cost-effectiveness in HIT diagnosis and management.

Safety and efficacy of antithrombotics in outpatients with symptomatic COVID-19: A systematic review and meta-analysis

BACKGROUND

Coronavirus disease (COVID-19) is a global health emergency, with well over six hundred million infections and over six million deaths to date. Besides other ramifications, it is also associated with inflammation and an augmented risk of thromboembolic complications. Despite this, the risks and benefits of antithrombotic drugs in patients with mild to moderate COVID-19 have not been well-established and remain controversial.

OBJECTIVES

To evaluate the safety and efficacy of antithrombotic drugs on mild to moderate symptomatic COVID-19 patients by performing an updated systematic review and meta-analysis.

METHODS

We queried electronic databases (PubMed, Cochrane Central, Scopus, and Embase) from their inception up to September 2022 for randomized controlled trials comparing antithrombotic drugs against placebo. The outcomes of interest were the need for hospital care, mortality, and thromboembolic events in the enrolled participants. Dichotomous outcomes were presented as risk ratio (RR) with 95 % confidence intervals (CIs) and were consolidated using random-effects model.

MAIN RESULTS

Five eligible studies (Rivaroxaban/Apixaban, two; enoxaparin, two; Sulodexide, one), consisting of 2,005 participants with mild to moderate COVID-19, were included. Pooled results show that antithrombotics, when compared to placebo, do not significantly reduce all-cause mortality (RR 0.51, 95 % CI 0.15-1.68; P = 0.27; I2 = 0), thromboembolic events (RR 0.78, 95 % CI 0.17-3.51; P = 0.74; I2 = 0), need for hospitalization (RR 0.73, 95 % CI 0.51-1.03; P = 0.08; I2 = 0), nor significantly increase clinically relevant non-major bleeding events (RR 2.36, 95 % CI 0.56-9.89; P = 0.24; I2 = 0). However, when Sulodexide was compared independently to other antithrombotics, it significantly reduced the need for hospitalization (RR 0.60, 95 % CI 0.37-0.95; P = 0.03).

CONCLUSIONS

Our pooled analysis was not able to establish statistically significant benefits or risks of using antithrombotic drugs in mild to moderate COVID-19 patients. To further improve our understanding of the efficacy, safety and risk profile of such a therapy, large sample randomized clinical trials are required on a wide scale.

Colchicine and the combination of rivaroxaban and aspirin in patients hospitalised with COVID-19 (ACT): an open-label, factorial, randomised, controlled trial

BACKGROUND

COVID-19 disease is accompanied by a dysregulated immune response and hypercoagulability. The Anti-Coronavirus Therapies (ACT) inpatient trial aimed to evaluate anti-inflammatory therapy with colchicine and antithrombotic therapy with the combination of rivaroxaban and aspirin for prevention of disease progression in patients hospitalised with COVID-19.

METHODS

The ACT inpatient, open-label, 2 × 2 factorial, randomised, controlled trial was done at 62 clinical centres in 11 countries. Patients aged at least 18 years with symptomatic, laboratory confirmed COVID-19 who were within 72 h of hospitalisation or worsening clinically if already hospitalised were randomly assigned (1:1) to receive colchicine 1·2 mg followed by 0·6 mg 2 h later and then 0·6 mg twice daily for 28 days versus usual care; and in a second (1:1) randomisation, to the combination of rivaroxaban 2·5 mg twice daily plus aspirin 100 mg once daily for 28 days versus usual care. Investigators and patients were not masked to treatment allocation. The primary outcome, assessed at 45 days in the intention-to-treat population, for the colchicine randomisation was the composite of the need for high-flow oxygen, mechanical ventilation, or death; and for the rivaroxaban plus aspirin randomisation was the composite of major thrombosis (myocardial infarction, stroke, acute limb ischaemia, or pulmonary embolism), the need for high-flow oxygen, mechanical ventilation, or death. The trial is registered at www.

CLINICALTRIALS

gov, NCT04324463 and is ongoing.

FINDINGS

Between Oct 2, 2020, and Feb 10, 2022, at 62 sites in 11 countries, 2749 patients were randomly assigned to colchicine or control and the combination of rivaroxaban and aspirin or to the control. 2611 patients were included in the analysis of colchicine (n=1304) versus control (n=1307); 2119 patients were included in the analysis of rivaroxaban and aspirin (n=1063) versus control (n=1056). Follow-up was more than 98% complete. Overall, 368 (28·2%) of 1304 patients allocated to colchicine and 356 (27·2%) of 1307 allocated to control had a primary outcome (hazard ratio [HR] 1·04, 95% CI 0·90-1·21, p=0·58); and 281 (26·4%) of 1063 patients allocated to the combination of rivaroxaban and aspirin and 300 (28·4%) of 1056 allocated to control had a primary outcome (HR 0·92, 95% CI 0·78-1·09, p=0·32). Results were consistent in subgroups defined by vaccination status, disease severity at baseline, and timing of randomisation in relation to onset of symptoms. There was no increase in the number of patients who had at least one serious adverse event for colchicine versus control groups (87 [6·7%] of 1304 vs 90 [6·9%] of 1307) or with rivaroxaban and aspirin versus control groups (85 [8·0%] vs 91 [8·6%]). Among patients assigned to colchicine, 8 (0·61%) had adverse events that led to discontinuation of study drug, mostly gastrointestinal in nature. 17 (1·6%) patients assigned to the combination of rivaroxaban and aspirin had bleeding compared with seven (0·66%) of those allocated to control (p=0·042); the number of serious bleeding events was two (0·19%) versus six (0·57%), respectively (p=0·18). No patients assigned to rivaroxaban and aspirin had serious adverse events that led to discontinuation of study drug.

INTERPRETATION

Among patients hospitalised with COVID-19, neither colchicine nor the combination of rivaroxaban and aspirin prevent disease progression or death.

FUNDING

Canadian Institutes for Health Research, Bayer, Population Health Research Institute, Hamilton Health Sciences Research Institute, Thistledown Foundation.

TRANSLATIONS

For the Portuguese, Russian and Spanish translations of the abstract see Supplementary Materials section.