VPB0279 - Anti-factor Xa-based risk stratification of children receiving therapeutic enoxaparin is associated with increased risk of recurrent/progressive thrombosis and hemorrhage: a retrospective cohort study

Sunday, July 10, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: Virtual

Presenting Author(s)

Wallace Bourgeois, MD

Instructor in Pediatrics
Dana-Farber/Boston Children’s Cancer and Blood Disorders Center, Harvard Medical School
Boston, Massachusetts, United States

Co-Author(s)

ED

Emily Drake

Pediatric Anti-Coagulation Nurse Practitioner
Division of Hematology and Oncology, Boston Children's Hospital and Harvard Medical School
Boston, Massachusetts, United States
JD

Julie Duzan

Pediatric Anti-Coagulation Nurse Specialist
Division of Hematology and Oncology, Boston Children's Hospital and Harvard Medical School
Boston, Massachusetts, United States
NC

Nan Chen

Biostatistician I
Dana-Farber/Boston Children’s Cancer and Blood Disorders Center
Boston, Massachusetts, United States
WL

Wendy B. London

Associate Professor of Pediatrics
Dana-Farber/Boston Children’s Cancer and Blood Disorders Center, Harvard Medical School, Boston, MA
Boston, Massachusetts, United States
NR

Nikitha Ramesh

Clinical Research Coordinator
Boston Children's Hospital
Boston, Massachusetts, United States
RK

Riten Kumar, MD, MSc

Associate Professor of Pediatrics
Dana-Farber/Boston Children's Cancer and Blood Disorders Center.
Boston, Massachusetts, United States

Background: Despite recent regulatory approval of direct oral-anticoagulants, enoxaparin remains a frequently prescribed anticoagulant in children. Patients at our quaternary-care center requiring therapeutic enoxaparin have been historically stratified to aim for high-risk (HR; target anti-factor Xa: 0.4-0.6 IU/mL) and standard-risk (SR; anti-factor Xa: 0.5-1 IU/mL) enoxaparin levels.

Aims: Principal objective of this observational study was to compare rates of recurrent/progressive thrombosis and hemorrhage (major/clinically-relevant non-major bleeding) for HR versus SR cohorts.

Methods: Permission from the research ethics board was obtained. Pediatric patients (≤18 years) diagnosed with venous-thrombosis between 06/01/2009 - 06/30/2020, who received therapeutic enoxaparin were eligible. Demographic data were abstracted from medical records. Assignment to HR or SR cohorts was at the treating physician’s discretion. Recurrent/progressive thrombosis and hemorrhage were defined per International Society on Thrombosis and Haemostasis guidelines. Standardized statistical methods were used to summarize data, Fisher’s exact test was used to compare variables between HR and SR cohorts.

Results: 881 patients received enoxaparin during the study-period of whom 315 did not meet eligibility criteria and were excluded. 565 patients (288 female) were analyzed (Figure 1). Mean (± SD) age at VTE diagnosis was 9.4 (±6.6) years. Mean duration of therapeutic anticoagulation for the entire cohort was 4.2 (±4.4) months. Demographic data are summarized in Table 1. 99 (17.5%) patients were initially allocated to the HR cohort. Rate of recurrent/progressive thrombosis was 21 (21.2%) in the HR cohort, compared to 48 (10.3%) in the SR cohort (p=0.003). Rate of major/CRNM bleeding was 20 (20.4%) in the HR cohort, compared to 38 (8.2%) in the SR cohort (p < 0.001).

Conclusion(s): Risk stratification of patients receiving therapeutic enoxaparin appears to be associated with a higher risk of both thrombus recurrence/progression and hemorrhage in patients allocated to a lower target anti-factor Xa (HR cohort). Analysis is ongoing to investigate additional predictors of thrombus recurrence/progression and hemorrhage.