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Adherence to hydroxyurea and clinical outcomes among children with sickle cell anemia
Sarah L Reeves1,2, Kevin J Dombkowski1, Hannah K Peng1
1Department of Pediatrics, Susan B Meister Child Health Evaluation and Research (CHEAR) Center, University of Michigan, Ann Arbor, MI, United States.
Insights
High adherence to hydroxyurea (>75%) is crucial for reducing vaso-occlusive crises and acute chest syndrome in children with sickle cell anemia. Nonadherence is common, highlighting the need for strategies to improve medication compliance.
Area of Science:
- Pediatric Hematology
- Pharmacology
- Public Health
Background:
- Hydroxyurea is a key treatment for sickle cell anemia (SCA), effectively reducing vaso-occlusive pain crises (VOC) and acute chest syndrome (ACS).
- Understanding the impact of adherence to hydroxyurea on clinical outcomes in pediatric SCA patients is critical for optimizing treatment efficacy.
Purpose of the Study:
- To investigate the association between hydroxyurea adherence levels and the incidence of VOC and ACS in children and adolescents with SCA.
- To determine the threshold of hydroxyurea adherence required for significant clinical benefit in pediatric SCA patients.
Main Methods:
- A retrospective cohort study utilizing Medicaid data from six US states (2005-2012).
- Inclusion criteria: children aged 1-17 years with SCA, enrolled in Medicaid for 3 years, and initiated on hydroxyurea.
- Medication Possession Ratio (MPR) was calculated to assess adherence; clinical outcomes (VOC-related ED visits/admissions, ACS encounters) were analyzed using multivariable Poisson models.
Main Results:
- The study included 515 children initiating hydroxyurea, with a median MPR of 0.53.
- Higher MPR quartiles were associated with lower predicted counts for ACS and VOC-related events.
- A statistically significant reduction in ACS visits was observed in the highest MPR quartile compared to the lowest.
Conclusions:
- Achieving high adherence to hydroxyurea (over 75%) is essential for minimizing negative clinical outcomes in pediatric SCA.
- Moderate to severe nonadherence to hydroxyurea appears prevalent in this population, underscoring the need for interventions to improve adherence.
- Developing and testing novel strategies to enhance hydroxyurea adherence is crucial for improving the management of sickle cell anemia in children.
Objective:
Hydroxyurea lowers the incidence of vaso-occlusive pain crises (VOC) and acute chest syndrome (ACS) among children with sickle cell anemia (SCA). Our objective was to assess the relationship between levels of adherence to hydroxyurea and clinical outcomes among children and adolescents with SCA.
Methods:
This retrospective cohort study included Medicaid data (2005-2012) from Florida, Illinois, Louisiana, Michigan, South Carolina, and Texas. The study population consisted of children 1-17 years old with SCA enrolled in Medicaid for 3 years. Among children that initiated hydroxyurea, the medication possession ratio (MPR) was calculated as the proportion of days covered by hydroxyurea. Six months after initiation of hydroxyurea, clinical outcomes were assessed through the end of the study period: numbers of VOC-related inpatient admissions and emergency department visits, and encounters for ACS. Multivariable Poisson models were used to predict outcomes by MPR quartile adjusting for previous healthcare utilization, state, and age.
Results:
Hydroxyurea was initiated by 515 children. The median MPR was 0.53 (interquartile range = 0.3-0.8). The annual median number of visits was 0.0 for ACS, 1.3 for VOC-related emergency department, and 1.4 for VOC-related inpatient admissions. For each outcome, the highest quartile of MPR had the lowest predicted count; this difference was significant for ACS visits when compared with the lowest quartile of MPR.
Conclusion:
This study demonstrated a high level of adherence (>75%) was essential to achieve a lower incidence of common negative clinical outcomes. Further, moderate and severe hydroxyurea nonadherence may be more common than previously appreciated among children, emphasizing the importance of developing and testing innovative strategies to increase adherence.
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