Background: Sickle Cell Disease (SCD) is among the world’s most common hereditary red blood cell disorders. It is associated with pervasive hemolytic anemia, episodes of vaso-occlusion producing extensive pain, progressing acute events and a high frequency of end organ insults with cumulative end organ damage. With approvals of therapeutic interventions, updated information on SCD acute event frequencies especially from real world data (RWD) is lacking.
Objectives: The objective of this study is to use RWD to comprehensively assess the most recent SCD acute event frequencies in the US.
Methods: This is a non-interventional, retrospective cohort study using Optum US-based EHR data from January 1st 2007 to December 31st 2021. The index date followed a 183-day baseline period after the SCD patients were identified. Patients were included if they had at least one inpatient or two outpatient SCD ICD-9-CM or ICD-10-CM codes at least 30 days apart. Follow up for the SCD acute events started at the index date and continued until a patient was censored (i.e., lost database activity, died, or the study period ended). The event frequency rate was estimated by dividing the number of acute events by total person time -- stratified by SCD genetic subtype, age group, and sex. Each patient could contribute multiple counts for all events except proteinuria. The period prevalence for acute events was also evaluated.
Results: A total of 18,227 SCD patients were included in this study of which the median age was 29 years old (range 0-89), 59% were women, and 81% were African American by self-report. The frequency rates (per 1,000 person years) of the SCD acute event types were: ischemic (177.3) and hemorrhagic (9.3) stroke, seizures (169.2), Medical Utilization (MU) VOC (1,318.6), Acute Chest Syndrome (ACS, 138.4), gross hematuria (7.1), avascular necrosis (12.8), renal papillary necrosis (1.2), hepatic sequestration (7.5), splenic sequestration (17.7), priapism (32.4), leg ulcers (14.0), proteinuria (7.1), and all-cause mortality (18.8). Most acute event outcomes were more frequent and prevalent among patients with Hb-SS genotype, adult patients and male patients.
Conclusions: To our best knowledge, this study provided one of the most recent SCD acute event frequency rates in the US using real world data following approval of hydroxyurea, Voxelotor, Crizanlizumab and L-glutamine as therapeutic interventions. It may serve as a reference for future SCD research. Comparing to results from other studies, the frequency rate for acute events such as ACS in this study may be similar; ischemic stroke in this study may be higher; avascular necrosis may be lower.
