Patients with Sickle Cell Disease and Venous Thromboembolism Experience Increased Frequency of Vasoocclusive Events
Authors: Lawrence Romy Carmen , Khan Sarah L , Gupta Vishal , Scarpato Brittany , Strykowski Rachel , Newman Julia , Sloan John Mark , Cohen Robyn T. , Nouraie Seyed Mehdi , Klings Elizabeth S 
Published: February 2020

Introduction
Patients with sickle cell disease (SCD) are at increased risk for venous thromboembolism (VTE). By age 40, 11-12% of SCD patients have experienced a VTE. VTE confers nearly a three-fold increase in mortality risk for individuals with SCD. We hypothesized that VTE increases subsequent SCD severity which may increase acute care utilization. We investigated the association between VTE and rates of vaso-occlusive events (VOE) and acute care utilization for individuals with SCD.
Methods
We performed a retrospective longitudinal chart review of 239 adults with SCD who received care at our institution between 2003 and 2018. VTE was defined as deep venous thrombosis (DVT) diagnosed by Duplex ultrasound or pulmonary embolism (PE) diagnosed by either ventilation-perfusion scanning or computed tomography angiography. Medical histories, laboratories and medication use for all subjects were obtained. For VTE patients, clinical data for 1- and 5- years post-VTE were obtained and compared to 1 year prior to the VTE. For non-VTE patients, data were obtained at baseline and compared to five years later. We evaluated all acute care visits for the presence of a SCD-related problem, specifically assessing if a VOE or acute chest syndrome (ACS) occurred. We calculated rates of VOE, ACS, Emergency Department (ED) visits and hospitalizations prior to and subsequent to a VTE and compared these to occurrence rates among those without VTE. Data were analyzed using Stata 14.2.
Results
In our cohort of 239 individuals with SCD, 153 (64%) were HbSS/HbSβ0 and 127(53%) were female. Fifty-six individuals (23%) had a history of VTE; 20 had a DVT (36%), 33 had a PE (59%), and 3 had both (5%). Patients with VTE had a higher frequency of prior history of ACS (p&lt;0.001), stroke (p=0.013), splenectomy (p=0.033), and avascular necrosis (p&lt;0.001) than those without a VTE. Prior to their VTE, these patients had higher white blood cell (11.8 x103 [9-15 x 103] vs 9.7 x103 [7-12 x 103], p=0.047) and platelet counts (378 x 103 [272-485 x 103] vs 322 x 103 [244-400 x 103], p=0.007) than those without a VTE. During five years of follow-up after a VTE, these patients had 6.32 (SD 14.97) ED visits per year compared to 2.84 (SD 5.93, p&lt;0.03) ED visits per year in those without a VTE. Ninety two percent of these ED visits were SCD-related; 73% were for VOE and 4% for ACS. Additionally, SCD patients with a VTE had an increase in all-cause hospital admissions (2.84 [SD 3.26] vs 1.43 [SD 2.86], p=0.003) and SCD-related hospital admissions (2.61 [SD 3.13] vs 1.23 [SD 2.74], p=0.001) per year compared to those without VTE.
Conclusion
VTE is a frequent complication in patients with SCD. Our study suggests that patients who experience a VTE have greater SCD severity as evidenced by increased VOE, ED and hospital utilization. These data suggest that VTE is not merely an isolated event in SCD patients and that it may either serve as an indicator of disease severity or contribute to overall disease pathophysiology.

Disclosures
Sloan: Abbvie: Other: Endpoint Review Committee; Stemline: Consultancy; Merck: Other: endpoint review commitee.