Comparison of Rethrombosis-Free Survival in Children Versus Adults Suffering from Antithrombin-, Protein C- and Protein S-Deficiency: An Observational Multicenter Cohort Study

Background: Venous thromboembolism [TE] is a multifactorial disease and antithrombin [ATD]-, protein C [PCD]- or protein S [PSD]-deficiency constitutes a major risk factor. Since screening for thrombophilia is controversial, individuals at high risk for recurrence who benefit from screening need to be identified. Primary study objective was to determinethe individual recurrence risk in children compared to adults with TE with respect to their thrombophilia status.

Methods: In 142 consecutively enrolled TE patients (children n=85; adults n=57) with ATD, PCD or PSD after exclusion of six children with purpura fulminans due to homozygous PCD or PSD we calculated i) the cumulative recurrence rates (CRR) at 1, 5 and 10 year following the first TE onset and, ii) in addition, the absolute recurrence risk (ARR) per 100 patient years (%).

Results: At first TE onset in univariate analysis a higher rate of unprovoked TE was found in children, whereas adults presented with a higher rate of a positive TE family history and a higher rate of recurrence: 40 out of 136 patients showed a second TE after withdrawal of anticoagulation (AC) or insufficient AC [n=6]. Two events in children were fatal [pulmonary embolism]. The overall CRR at 1, 5 and 10 years was 10.9%, 20.4% and 29.2% with total ARR [95% CIs] of 5.3 [3.4-7.8] in adults compared to 2.1 [1.0-5.3] in children [p=0.004]. Whereas the ARR was no different between adults and children in ATD patients [5.1 versus 4.7; p=0.85] and in symptomatic PCD subjects [3.9 versus 1.6; p=0.17], adults with PSD showed a higher ARR compared to children [6.3 versus 0.1; p=0.001]. Positive family TE history did not predict recurrence.

Conclusion: Given the high ARR of 5.3% in adults and 2.1% in children we suggest screening for ATD, PCD and PSD in adult and pediatric TE patients. The high rate of ARR should be taken into account when initiating future therapeutic trials. Duration and intensity of AC should be carefully reevaluated in patients with ATD, PCD or PSD.