Adherence to Hydroxyurea Therapy in Children with Sickle Cell Anemia

ObjectivesTo assess adherence to hydroxyurea therapy in children with sickle cell anemia (SCA), evaluate the association between adherence and hematologic profile, and identify barriers and facilitators of adherence.Study designChildren with SCA (n=75) receiving hydroxyurea were recruited for a single-institution cross-sectional study. The primary outcome was association between treatment adherence and percent fetal hemoglobin (HbF).ResultsGood adherence was estimated at 82% with visual analog scale, 84% with Morisky score, 85% with medical provider report, 77% with clinic visits, and 49% on the basis of pharmacy refills. Increase in HbF was moderately associated with good adherence as measured with the parent/proxy Morisky score (r=−0.39; 95% CI, −0.58–0.17; P < .01) and prescription refills (r=0.39; 95% CI, 0.16–0.57; P < .01). The number of pharmacy refills and the Morisky score explained 23% of the variation in HbF response.ConclusionsAdherence was ≥75% with 4 of 5 measures. Pharmacy refills and the Modified Morisky Scale may be used to identify children at high risk for poor response because of non-adherence and children with good adherence with poor response because of individual pharmacodynamics. Future research should prospectively compare adherence measures and evaluate methods to improve treatment adherence.