Review of economic studies of sickle cell disease and adherence to hydroxyurea and clinical and economic outcomes among Texas Medicaid enrollees with sickle cell disease

Sickle cell disease (SCD) is a rare, inherited blood disorder that affects approximately 100,000 Americans. SCD was recognized as a societal health burden due to pain crises and complications resulting in costly healthcare utilization. This dissertation: 1) summarized the economic burden of SCD in the U.S.; 2) assessed hydroxyurea medication adherence and its association with vaso-occlusive crisis (VOC)-related events and healthcare utilization and costs. The systematic review (N=21 articles) revealed mean total SCD healthcare costs (2019 USD) ranged from $19,464 to $32,446/patient/year, which was 1.7 to 2.9 times greater than the overall population. The retrospective cohort study used Texas Medicaid data from 09/01/2011-08/31/16 with individuals who: 1) were between 2-63 years, 2) had at least one hydroxyurea prescription claim and were treatment naive, and 3) were continuously enrolled. Medical and pharmacy claims were analyzed for over one year to examine their medication use patterns (hydroxyurea adherence and persistence, and pain medication use) and VOC-related healthcare utilization and costs. The association between hydroxyurea adherence (Medication Possession Ratio; MPR) and VOC-related healthcare utilization were assessed using multivariate analyses. A total of 1,035 patients (18.8±12.5 years) were included. Among them, 20.9% were adherent to hydroxyurea (defined as MPR≥0.8) and mean MPR was 0.50 (± 0.30). In the 12 months following hydroxyurea initiation, 771 (74.5%) of the patients experienced ≥1 VOC events (4.1±5.1). After adjusting for covariates, being adherent to hydroxyurea was significantly (p<0.05) associated with beneficial VOC-related health outcomes including a decreased risk and lower hazard rate of VOC events, fewer VOC events, and a shorter hospital LOS. Regarding all-cause and SCD-related healthcare utilization and expenditures, being adherent to hydroxyurea was significantly (p<0.05) associated with decreased hospitalizations and ED visits, increased outpatient visits and prescriptions, and lower total SCD-related healthcare expenditures. These study findings, the high economic burden of SCD and low hydroxyurea adherence, highlight the need for multi-stakeholder efforts to improve hydroxyurea adherence among the SCD population to improve both clinical and economic health outcomes.