Hemostasis and Thrombosis Centers Pilot Sites Registry: Thrombophilia Evaluation in Children.
Authors: Thornburg Courtney , Beckman Michele , Michaels Lisa , Manco-Johnson Marilyn , Dowling Nicole , Pipe Steven , Kulkarni Roshni 
Published: October 2019

Abstract
A family history (FH) of thrombophilia may prompt a referral to a pediatric thrombophilia clinic. The International Society of Thrombosis and Haemostasis recommends a step-wise thrombophilia evaluation for children with venous thrombosis, but there are no screening recommendations for asymptomatic children with a FH of thrombophilia. There is limited data on how many children are evaluated by a pediatric hematologist for a FH of thrombophilia or how these children are managed. We utilized the Centers for Disease Control and Prevention (CDC) Thrombosis and Hemostasis Centers Pilot Sites Registry to characterize children without a personal history of thrombosis who are referred to Thrombosis Centers (TCs). The CDC initiated the registry between eight TCs, including four pediatric sites. We queried the database for pediatric subjects, who enrolled in the registry between August 2003-March 2006. Data collection included referral patterns, laboratory and radiological tests ordered, diagnosis, and treatments. Three hundred thirty-two subjects were identified, ages 0–17 years (average 9 years). Fifty-five (16.6%) have no personal history of thrombosis. Among the 55 asymptomatic children 4 (7.3%) were referred exclusively for a FH of thrombosis without thrombophilia, 12 (21.8%) were referred exclusively for a FH of thrombophilia without a FH of thrombosis, 11 (20.0%) were referred for a FH of both thrombosis and thrombophilia, and 28 (50.9%) did not have a FH of thrombosis or thrombophilia. The latter subjects may have been referred to the TCs for anticoagulation management or for evaluation of a condition associated with thrombophilia such as migraine. No asymptomatic subjects were referred from the in-patient setting, 48 (87.3%) were referred from the out-patient setting, and 7 (12.7%) were self-referred. Of the 55 asymptomatic children, 19 (34.5%) were referred with a prior diagnosis of thrombophilia. Table 1 compares testing at the TCs of symptomatic and asymptomatic subjects. Three asymptomatic subjects with a FH of thrombosis and thrombophilia received anticoagulation prophylaxis, and 3 subjects received a recommendation for prophylaxis for future high risk situations. In summary, 16.6% of children enrolled in the CDC registry have no personal history of thrombosis. A significant proportion of these asymptomatic children have testing for prothrombotic risk factors prior to referral and at the TCs. We are conducting research to determine who and when to screen for thrombophilia, potential complications of such testing, when to provide genetic counseling, and optimal clinical application of the results.
Thrombophilia Testing at Pediatric Thrombosis Centers % subjects tested for Genetic tests Anticoagulants/Antiphospholipid antibodies Clotting factors Screening tests Lipids/Homocysteine All (n=332) 42.5 54.8 43.7 56.6 36.5 Symptomatic (n=277) 38.6 52.7 44.0 57.8 32.1 Asymptomatic (n=55) 61.8 65.5 41.8 50.9 58.2 Among asymptomatics with: FH of thrombosis (n=4) 100 100 25 100 100 FH of thrombophilia (n=12) 75 75 41.7 41.7 58.3 FH of thrombosis and thrombophilia (n=11) 72.7 63.6 27.3 36.4 81.8 No FH (n=28) 46.4 57.1 50 53.6 42.9