Evaluation of Factors Influencing Health Literacy in Adolescents and Adults with Sickle Cell Disease
Authors: Bhatt Nidhi , Calhoun Cecelia , Hodges Jason R. , Nwosu Chinonyelum , Kang Guolian , King Allison A. , Zhao Xiwen , Hankins Jane S. 
Published: November 2019

Introduction
In the United States 36% of adults have limited health literacy, which is associated with poor health outcomes (Kutner et al. National Assessment of Adult Literacy.2006). Health literacy is defined as "the capacity to obtain, process and understand basic health information and services needed to make appropriate health decisions" (Nielsen-Bohlman et al. National Academies Press.2004). Health literacy is understudied in sickle cell disease (SCD), a genetic disease affecting a minority population in the United States. SCD Preventive treatment requires patient engagement, therefore health literacy is an important determinant of health outcomes in SCD. Previous studies reported Health literacy in adolescents with SCD is suboptimal (Perry et al. J Pediatr Nur.2017), but few studies have investigated factors influencing health literacy in this population. Health literacy can be impacted by many factors such as cognition, socioeconomic status, education level and gender. This study evaluated health literacy level and factors that influenced Health literacy in adolescents and adults with SCD. In addition, we assessed the relationship of health literacy level and Hydroxyurea therapy use, one of only two FDA-approved disease-modifying therapies for SCD.
Methods
This was a cross- sectional study of adolescents and adults with SCD performed at St. Jude Children's Research hospital and St. Louis Children's hospital. Adolescents and adults ages 15 to 45 years completed a health literacy assessment using the newest vital sign (NVS). NVS is a validated tool with 6 questions that tests reading, mathematics and comprehension based on a nutrition label (Weiss et al. Ann Fam Med.2005). Score of 0-1 suggests high likelihood of limited health literacy, 2-3 indicates possibility of limited health literacy and 4-6 almost always suggests adequate health literacy. Self-reported demographic information was collected such as educational level, household income, age, sex, race. Additionally, SCD genotypes and hydroxyurea utilization were confirmed through chart review.
Results
A random sample of 125 adolescents and adults with SCD was evaluated (Table 1): 34 (28.1%) had Hb SC or Hb Sβ+-thalassemia, 87(71.9%) had Hgb SS or Hgb Sβ0-thalassemia, and 4 participants had unknown or other genotypes. Limited health literacy was prevalent, only 40 (32%) of subjects had adequate literacy, median NVS score was 2 for all participants. Participants with Hgb SS/Hgb Sβ0-thalassemia were more likely to be on hydroxyurea (p<0.001, Chi-square test). NVS scores in subjects with less severe genotype were not significantly different compared to more severe genotypes (p=0.2, Man-Whitney-Wilcoxon test/MWW). There was no difference in health literacy scores between those on hydroxyurea and not on hydroxyurea (p=0.24, MWW test), however despite low health literacy being prevalent, 85 (68%) subjects with Hb SS or HbSβ0-thalassemia were on hydroxyurea. Income level was significantly different between patient on hydroxyurea not on hydroxyurea (p= 0.034, Fisher's exact test). In addition, patient whose income was $35000 or more were found to have a higher NVS score (p=0.012, Kruskal-Wallis test) (figure 1). Subjects with high NVS scores were significantly older (p=0.026, Analysis of variance test), over all education was significantly associated with health literacy (p=0.003, Fisher's exact).
Conclusion
This study shows a low prevalence of adequate health literacy amongst adolescents and adults with SCD. Our data corroborate previous literature which has reported limited health literacy in this population as well adds granularity to the factors that may influence this suboptimal outcome. There was a statistically significant association between health literacy, income level and education level in adolescents and young adults with SCD. Further, health literacy was not significantly associated with sickle cell genotype or hydroxyurea use. This study highlights the social determinants of health and specific need to address health literacy in SCD patients. To optimize the care of adolescents and young adults with SCD, targeted multimodal interventions that are tailored to low health literacy levels should be employed to reduce morbidity and mortality in this vulnerable population.

Disclosures
Kang: MBIO: Other: St. Jude Children's Research Hospital has an existing exclusive license and ongoing partnership with Mustang Bio for the further clinical development and commercialization of this XSCID gene therapy. King:Amphivena Therapeutics: Research Funding; Bioline: Consultancy; Celgene: Consultancy; Cell Works: Consultancy; Incyte: Consultancy; Magenta Therapeutics: Membership on an entity's Board of Directors or advisory committees; Novimmune: Research Funding; RiverVest: Consultancy; Tioma Therapeutics (formerly Vasculox, Inc.):: Consultancy; WUGEN: Equity Ownership. Zhao:MBIO: Other: St. Jude Children's Research Hospital has an existing exclusive license and ongoing partnership with Mustang Bio for the further clinical development and commercialization of this XSCID gene therapy. Hankins:NHLBI: Research Funding; National Committee for Quality Assurance: Consultancy; Global Blood Therapeutics: Research Funding; NHLBI: Honoraria; ASPHO: Honoraria; LYNKS Foundation: Research Funding; Novartis: Research Funding; Bluebird Bio: Consultancy.