Genotype Differences and Hydroxyurea Utilization Among Adults With Moderate to Severe Sickle Cell Disease

Hydroxyurea (HU) remains underutilized in adults with sickle cell disease (SCD) despite proven benefits. Current HU guidelines primarily target sickle cell anemia (SCA), overlooking other genotypes.

This study examined HU utilization patterns across genotypes among adults considered to have moderate to severe SCD manifestations by the 2014 National Heart, Lung, and Blood Institute (NHLBI) guideline criteria and identified factors associated with early HU use.

This retrospective cohort study analyzed electronic health records from the University of Pittsburgh Medical Center (2014-2024) of adults with SCD experiencing three or more vaso-occlusive crises (VOCs) within 12 months. HU utilization rates, stratified by genotype, were assessed at 30-, 90-, 180-, and 365-day intervals after the third VOC episode (index date). Multivariable logistic regression was used to identify factors associated with HU use within 90 days post-index.

Among 411 adults with moderate to severe SCD (≥ 3 VOCs within a year), with a mean age of 42.4 ± 17.9 years and 61.3% female, only 19.5% received HU within 90 days post-index. Although 42.8% of SCA patients received HU within 1 year, only 8.0% of non-SCA patients received the treatment. The SCA genotype was the strongest predictor of HU use (odds ratio [OR] = 4.5, 95% confidence interval [CI]: 2.4-8.7), followed by pulmonary complications. Additional barriers included older age.

Despite guideline recommendations since 2014, HU remains underutilized. Non-SCA patients meeting the severity threshold for HU use are consistently undertreated, highlighting an urgent need for studies establishing HU safety and efficacy in non-SCA genotypes. Future studies should also address age barriers to optimize HU use.