Electronic Theses and Dissertations





Date of Award


Document Type

Dissertation (Access Restricted)

Degree Name

Doctor of Philosophy



Committee Chair

Vikki Nolan

Committee Member

James Gurney

Committee Member

Xinhua Yu

Committee Member

Jane Hankins


Sickle cell disease (SCD) is an inherited hematologic disorder in which abnormal hemoglobin results in misshapen red blood cells. SCD results in increased morbidity including pain crises, acute chest syndrome and chronic organ damage, often requiring acute medical care and hospitalization. We conducted three epidemiologic studies related to birth prevalence, access to care, and chronic organ damage in children with SCD. First, we evaluated SCD and sickle cell trait (SCT) birth prevalence in Shelby County, TN from 2002-2012. The birth prevalence among African Americans was 3.5 (95% CI: 3.1, 3.9) per 1000 live births for SCD and 68.1 (95% CI: 66.5, 69.7) per 1000 live births for SCT. We observed higher birth prevalence of SCD and lower birth prevalence of SCT than expected based on national estimates. Next, the association between travel distance from home to St. Jude Children's Research Hospital, a comprehensive sickle cell center, and the rate of clinic visits and hospitalizations among children with SCDwas studied. We found patients =35 miles, indicating distance may be a barrier to health care access. Bias analysis suggested that under-reporting could explain the observed differences in hospitalization rates if 30%of patients who lived >=35 miles from the hospital under-reported six hospitalizations over six years. The final study evaluated potential bias from missing data in a previously published multi-center randomized, placebo-controlled trial of hydroxyurea therapy on spleen and kidney function among infantswith SCD. Thirteen percent and 31% of randomized subjects did not have follow-up data for the spleen and kidney objectives, respectively. We did not find evidence of bias from missing data in the kidney objective, however, the true effect of hydroxyurea on spleen function could have been underestimated due to differential attrition. Additionally, even if the effect of hydroxyurea on spleen function was attenuated substantially due to missing data, the magnitude of the effect of hydroxyurea is likely smaller than originally hypothesized in the clinical trial.


Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.