Dissertation Defense Announcement

 School of Public Health announces the Final Dissertation Defense of

Joacy Mathias

for the Degree of Doctor of Philosophy

October 28, 2019 at 08:30 AM in Robison hall- Room 217

Advisor:  Vikki Nolan


ABSTRACT: The use of hydroxyurea (HU) reduces sickle cell disease (SCD)-related complications and health care utilization. Young adults transitioning to adult care have difficulty adhering to HU therapy (or may not be receiving HU) and have increased healthcare utilization when compared to their younger and older counterparts, due to various challenges. There is a lack of consensus about dosing strategies for HU due to fear of toxicities. We evaluated the association of different levels of HU adherence and healthcare utilization (hospitalizations, ED visits, and transfusions rates) among transitioning young adults (18 to 25 years) when compared to the pediatric (>18 years) and older (<25 years) groups, using state-wide claims data. We concluded that HU prescription prevalence was suboptimal in all three age groups of our study. Among those who initiated HU, as the HU percent prescription adherence increased the rate of hospitalizations, ED visits, and transfusions decreased. Females between ages 19 to 25 years had lower HU prevalence and medication possession ratio when compared to males. We estimated the association between the proportion of time a patient suspends HU treatment and its association with health-care utilization among pediatric, transitioning younger and older adults. those who suspend their treatment for extended periods have two to five times increased rate of health-care utilization, particularly among young adults. Young males who discontinued their treatment had a significantly increased rate of health-care utilization than females. The results of the above two studies may provide evidence to support HU adherence. We performed a meta-analysis comparing hematological toxicities between fixed and escalated dosing strategies in studies published between 2010 to 2015. Our meta-analyses show that summarized neutropenia and thrombocytopenia incidence rates are higher when using escalated dosing than fixed dosing. Summarized hepatic and renal toxicities' incidence rates were higher in fixed doses than the escalated doses. However, a small number of studies reporting toxicities related information, imprecise summarized incidence rates, and high heterogeneity between the studies may have affected our results. A randomized clinical trial to compare toxicities between fixed and escalated dosing strategies may help establishing a consensus of HU dosing method.