Study Determines Low Adherence to Hydroxyurea Treatment Among Children, Adolescents

Children and adolescents with sickle cell anemia (SCA) showed low adherence to treatment with hydroxyurea, according to a multi-state study in the U.S.

The research, “Hydroxyurea use among children with sickle cell anemia,” was published in the journal Pediatric Blood & Cancer.

Hydroxyurea is a medicine used to lessen the frequency of pain crises in people with SCA. Although National Heart, Lung, and Blood Institute (NHLBI) guidelines from 2002 to 2014 already recommended starting treatment with hydroxyurea among children and adolescents with symptoms  such as frequent pain, history of acute chest syndrome, or severe anemia, a 2014 revision broadened this recommendation to all SCA children 9 months and older.

Despite its clinical and economic benefits, center-based and single-state reports indicated low levels of hydroxyurea use in these children. Given the lack of data from larger studies, as well as limited information about whether hydroxyurea use varies over time, researchers at University of Michigan and the Baylor College of Medicine conducted a multi-state study to characterize the use of this therapy before the release of the revised NHLBI guidelines.

The scientists identified children and adolescents (age 1-17 years) with SCA and enrolled at least one year in Medicaid from 2005 to 2012. The participants were in six states with average to high prevalence of SCA — Florida, Illinois, Louisiana, Michigan, South Carolina, and Texas. Because  approximately 90% of children with SCA are enrolled in Medicaid at some point, the team expected this approach would include a large proportion of targeted patients.

Administrative claims were used to summarize the number of days’ supply of hydroxyurea dispensed, and categorized by state and year.

A total of 7,963 patients were identified (3,858 females, or 48%), corresponding to 22,424 “person-years,” which is a measure that adds up actual follow-up duration in each patient and is higher with more years in study. Florida showed the highest number of person-years (6,816, 30%) and South Carolina the lowest (2,122, 9%). The average patient age in 2015 was 8.8 years, which did not vary significantly over the study period or across different states.

Using person-years, 77.9% had no hydroxyurea use, while 19.5% used this therapy more than 30 days within a year. The average number of annual days’ supply of hydroxyurea was 189 among patients using this treatment. In turn, the annual proportion of patients with at least 300 days’ supply ranged from  14.9% in 2009 to 19.6% in 2005.

“This suggests that even among children who use hydroxyurea, medication adherence is low, and strategies to increase adherence to hydroxyurea therapy among children with SCA are critically needed,” the scientists wrote.

The data also showed that among those using hydroxyurea, older age and more inpatient hospital admissions were associated with lower odds of at least 300 days’ supply of the therapy. In contrast, more outpatient visits correlated with higher odds of such use.

“These findings establish a baseline by which to assess potential future changes in hydroxyurea use following the 2014 NHLBI guidelines,” the team added.