Hydroxyurea Use in Sickle Cell Disease Patients in a Florida Medicaid Population.
Authors: Ritho Jane N. , Mayhew Dionne Y. , Hartzema Abraham G. , Liu Huazhi , Lottenberg Richard 
Published: October 2019

Background: Efficacy of hydroxyurea (HU) was demonstrated in the Multicenter Study of Hydroxyurea in Sickle Cell Anemia (MSH) placebo-controlled randomized clinical trial with a reduction in average crisis rate (weighted mean difference −2.80; CI −4.74 to −0.86). HU was FDA-approved in 1998 for treatment of adults with sickle cell anemia experiencing recurrent painful episodes. An observational 9 year follow-up study of the MSH cohort demonstrated improved survival for patients taking HU. Purpose: To examine adoption and utilization of HU in SCD patients in a Medicaid population.

Methods: A retrospective cohort study was conducted using Florida Medicaid eligibility, medical and pharmacy data for January 1, 2001 to December 31, 2005. The Medicaid database consists of medical and outpatient pharmacy utilization and reimbursement claims. SCD patients aged between 16 and 64 years with at least one inpatient or two outpatient SCD diagnosis claims (ICD-9-CM 282.6x), and meeting continuous eligibility criteria were included. HU adoption was determined by the presence of at least one HU pharmacy claim using National Drug Codes. Adherence to HU was calculated using the medication possession ratio (MPR) defined as the cumulative daily dose dispensed (excluding the last prescription refill and hospitalizations) divided by the time period between the first and last HU prescription (Rx) dispensed. Descriptive and bi-variate analyses were used to assess the relationship between patient characteristics, treatment and utilization of medical resources.

Results: The mean age of the 2,301 SCD patients identified is 25 years ± 10.9(SD). Of those, the majority were female (64%) and younger than 25 years of age (60%). During the study eligibility period, 72% had at least one SCD-related emergency department visit, 88% at least one hospitalization and 53% at least one inpatient claim for SCD with pain crisis. During the study period, 33.4% of the patients had ≥ 3 hospitalizations for SCD with pain crisis in any 12 month period. Approximately one-third of patients had red blood cell transfusions (36%) but only 4.4% had a claim for iron-chelation. Of all SCD patients 26% used outpatient opioid medications with 65.4% receiving slow-release formulations. Nearly 17% of the cohort (n=384) had at least one pharmacy claim for HU. Compared to non-HU users, HU users were more likely to be males (OR 1.79; CI 1.44–2.23), aged ≥ 25 years (OR 1.35; CI 1.08–1.71), with a history of using slow-release opioid medications (OR 5.95; CI 4.65–7.59) or receiving red cell transfusions (OR 4.21; CI 3.35–5.31). Of those SCD patients eligible to receive HU according to the MSH criteria (≥ 3 hospitalizations a year for SCD crisis), only 38% received at least one HU Rx (OR 11.78, CI: 8.26–16.80). For those patients receiving at least two HU Rx, only 30.2% had a MPR of ≥ 0.60 (see Table).

Conclusions: The prevalence of HU use in this Medicaid population is low. Our results suggest that only a small subset of SCD patients receive HU prescriptions consistently. Early therapy drop out and low adherence rates are common in patients prescribed HU. Interventions to promote physician adoption and prescribing of HU are needed, as are efforts to increase patient adherence.

HU Possession Ratio Number of patients (%) 0 – < 0.2 69 (28.6) 0.2 – < 0.4 46 (19.1) 0.4 – < 0.6 53 (22.0) 0.6 – < 0.8 36 (14.9) > 0.8 37 (15.4) Total 241 (100)