Outcomes in Children with Provoked Venous Thrombosis and Antiphospholipid Antibodies: Findings from the Kids-DOTT Trial

• aPL are common in pediatric patients with acute provoked VTE, and are mostly transitory and clinically insignificant

• Pediatric patients with APS and provoked VTE appear at increased risk of recurrent VTE compared to those with transitory or low titer aPL

Few studies have prospectively evaluated the incidence and outcomes in children with provoked venous thromboembolism (VTE) and transient or persistent antiphospholipid antibodies (aPL). We compared outcomes of patients <21 years old with a first-episode acute provoked VTE and positive aPL at diagnosis enrolled in the Kids-DOTT trial. aPL were tested at enrollment and, when positive, repeated at 6 weeks post-VTE. Subsequent testing was performed at discretion of the treating hematologist. Of 524 patients, 116 (22%) had positive aPL at enrollment. At follow-up, 70 (60%) had transient (n=66) or low titer aPL (n=4), 11 (10%) had persistent aPL meeting criteria for antiphospholipid syndrome (APS), and 35 (30%) had no repeat testing. Patients with APS were older (15.8 vs. 9.9 years, p=.014), and had a statistically significant higher risk of symptomatic recurrent VTE (18% vs. 1%, OR: 12.2 [1.4 - 108], p= .025), and a statistically non-significant but clinically meaningful difference in the risk of anticoagulant-related clinically-relevant bleeding (9% vs. 0%, OR: 20.1 [0.7 - 558], p=0.077) compared to those in the transient or low titer aPL group. In conclusion, aPL are common in young patients with acute provoked VTE and are mostly transitory and clinically insignificant. Patients with APS and provoked VTE appear to have an increased risk of recurrent VTE compared to patients with transitory or low titer aPL. Future collaborative studies should investigate the optimal VTE management of children with provoked VTE who meet criteria for APS.