Incidence of Pediatric VTE in Durham County, North Carolina
Authors: Borst Alexandra , Saber Ibrahim , Thames Elizabeth , Reyes Nimia , Beckman Michele , Ortel Thomas L. 
Published: October 2019

Abstract
Introduction
There is no national surveillance system for venous thromboembolism (VTE) despite the associated morbidity, mortality and economic burden on the health care system. Estimates of the incidence of VTE in the U.S. range from 1-2 cases per 1,000 people, or approximately 300,000-600,000 cases per year. The estimated incidence in children is lower, ranging from 1-10 per 100,000, with the period of greatest risk for VTE < 1 year and in the teenage years. It has been observed that most children with VTE have a serious underlying medical condition. The contribution of inherited thrombophilia to VTE in children remains not well established.
Methods
All patients with VTE in Durham County, North Carolina (NC), were identified as part of a VTE Surveillance Project supported by the Centers for Disease Control and Prevention from April 2012 through March 2014. Surveillance included an information technology-based electronic medical record review of diagnosis and specific treatment codes combined with manual review of radiographic imaging and autopsy reports. De-identified data were collected from the three hospitals in the county (Duke, Duke Regional, and the Durham VAMC) and entered into a REDCap database for analysis.
Results
The estimated population of Durham County during the study period was ~268,000, and ~69,000 of these individuals were < 20 years of age (25.7%). There were a total of 726 new cases of VTE in the county during the study period, for an estimated overall annual incidence of 0.135% (1.35 cases per 1000 per year). Of the total cohort, 19 individuals were less than 25 years of age (Figure 1), but only 8 patients were younger than 20 years, for an estimated annual incidence of VTE in the pediatric subset of 0.006% (6 cases per 100,000 per year). All pediatric VTE cases were identified at Duke University Medical Center. Table 1 lists characteristics of the pediatric population identified. The majority of patients were in their teenage years (75%) and there were no infants. One patient had a prior history of VTE and was taking warfarin at the time of diagnosis. None of the patients received primary pharmacologic thromboprophylaxis. One patient with intracranial hemorrhage did not receive any anticoagulant therapy after diagnosis of a deep vein thrombosis (DVT). One patient was treated with argatroban because of a history of heparin-induced thrombocytopenia, and the remainder were treated with enoxaparin or heparin. None were treated with fibrinolytic therapy or implantation of an IVC filter. Three patients underwent a thrombophilia evaluation, and one was heterozygous for the prothrombin gene mutation.
Table 1. Pediatric Patient Characteristics Age (yrs) Sex Race/Ethnicity VTE Event Diagnostic Imaging Prothrombotic Risk Factors Hemorrhagic Risk Factors 4 M White DVT MRI Hemoglobinopathy, CVC 5 M Hispanic DVT US CVC ICH, DIC 17 F White DVT; PE MRI;VQ Scan OCP, Prothrombin gene mutation 18 F White DVT US Immobility ICH 18 M African American DVT US CVC; relative immobility, trauma 19 M African American PE CT CrohnÕs disease, smoking 19 M African American DVT US Prior VTE; ?Protein S deficiency, obesity 19 F African American PE CT Contraceptive patch PE = pulmonary embolus, US = ultrasound, CT = computed tomography scan, VQ = ventilation/perfusion scan, MRI = magnetic resonance imaging, CVC = central venous catheter, OCP = oral contraceptive pill, ICH = intracranial hemorrhage, DIC = disseminated intravascular coagulation
Discussion
Although 25.7% of individuals living within Durham County, NC are < 20 years of age, this age group represents only ~1.1% of the total number of individuals identified with VTE. The incidence of pediatric VTE was approximately 6 per 100,000 per year, consistent with prior reports. VTE was more common in African Americans in the pediatric patients, which we have observed in all age groups in this surveillance study. Most patients were teenagers, and one or more acquired prothrombotic risk factors were present in all. We did not identify any infants (age < 1 year) in this study, likely reflecting the small sample size and geographic restriction of the study. The type of VTE events observed and initial treatment strategies were similar to adult patients studied. A more accurate assessment of pediatric VTE within a tertiary care academic medical center will need to capture patients from a broader geographic distribution to represent the referral patterns for these complex patients.

Disclosures
Ortel: Instrumentation Laboratory: Consultancy; Instrumentation Laboratory: Research Funding; Eisai: Research Funding; Daiichi Sankyo: Consultancy.