OBJECTIVES : To determine if adherence to hydroxyurea is associated with all-cause and disease-related healthcare expenditures among sickle cell disease (SCD) patients.

METHODS : This retrospective study used Texas Medicaid claims data from 9/1/11-8/31/16. The index date was the date of hydroxyurea initiation. Patients who were between 2 and 63 years old, had ≥1 hydroxyurea prescription from 3/1/12-8/31/15, had no hydroxyurea prescription 6 months prior to the index date, had ≥1 inpatient or ≥2 outpatient SCD diagnoses and no diagnosis of other indications for hydroxyurea use between 6 months before and 1 year after the index date were included. Hydroxyurea adherence (Medication Possession Ratio; MPR) and all-cause and SCD-related healthcare expenditures (hospitalization, emergency department visits, outpatient visits, prescriptions, and total) for 1 year following the index date, and covariates (age, gender, evidence of blood transfusion and transplantation, complications, comorbidity, and vaso-occlusive crises) were measured. Generalized linear models with gamma distributions and log link were used for multivariate analyses.

RESULTS : A total of 1,035 patients met the inclusion criteria. Their average age was 19 years (SD=12) and 49.7% were male. Of these, 20.9% were adherent to hydroxyurea (defined as MPR > 0.80) and mean MPR was 0.50 (±0.30). In the 12 months following hydroxyurea initiation, all-cause and SCD-related total healthcare expenditures were $27,760 (SD=$43,450, median=$13,252) and $19,879 (SD=$33.550, median=$8,024), respectively. After adjustment for covariates, being adherent to hydroxyurea was associated with 20.4% lower total SCD-related healthcare expenditures (Relative Risk [RR]:0.796, 95% CI:0.651-0.973), lower all-cause and SCD-related hospitalization expenditures (RR:0.802, 95% CI:0.647-0.994; RR:0.793, 95% CI:0.636-0.990, respectively), and higher all-cause and SCD-related prescription expenditures (RR:1.786, 95% CI:1.421-2.243; RR:1.851, 95% CI:1.667-2.054, respectively).

CONCLUSIONS : Being adherent to hydroxyurea among SCD patients was associated with lower total SCD-related healthcare expenditures given that higher prescription expenditures were offset by lower hospital expenditures.