Greater Barriers to Hydroxyurea (HU) Associated with Poorer Health Related Quality of Life (HRQL) in Youth with Sickle Cell Disease

Background: Across pediatric chronic illness, poor adherence to medical treatment is common. Despite known benefits, HU adherence in adolescents and young adults is often poor. Barriers are often assessed by either parent-proxy or youth perspective. The purpose of this study was to examine HU barriers from both perspectives in a sample of poorly adherent youth ages 10-18 years and their parents who participated in the Hydroxyurea Adherence for Personal Best in Sickle Cell Disease (SCD), "HABIT," a feasibility trial (NCT02029742) of a 6 month intervention. Our earlier work suggests that youth assigned to the HABIT intervention improved HbF¹, an adherence biomarker, and HRQL². In this study we further examined these relationships.

Methods: We examined self-reported barriers to HU at 0, 3 and 6 months, its association with generic and disease-specific HRQL and the impact of a community health worker (CHW) intervention on barrier reduction. Barriers were measured using the Adolescent Medication Barriers Scale³ (17 items; 3 subscales) and its parent counterpart, Parent Medication Barriers Scale (16 items; 4 sub scales); both scales were modified for HU use by adding 9 items⁴to capture knowledge and beliefs about HU. Barriers reported by ≥25% of the sample were considered to be common. Parent proxy and youth reported generic and disease-specific HRQL were measured at the same intervals by PedsQL and PedsQL Sickle Cell module⁵,respectively. Dyads randomized to the intervention received support from a CHW. Data were analyzed using Cronbach's alpha, descriptive statistics, Spearman correlation coefficients and linear growth models controlling for group assignment and time.

Results: 28 parent-youth dyads participated (youth age 14.3 ± 2.6 years, 43% female, 50% Latino). Internal reliability of the barrier scale was high for parent (alpha=0.88) and youth (alpha=0.91) total scores and all most subscales. On average, total barriers were greater for youth compared to parents (5.0±3.9 and 3.5±3.2); the majority (82.1% parents, 85.7% youth) of the sample reported one or more barriers. Greater total barriers were inversely associated with total generic (parent r=-0.43, p=0.03; youth r=-0.44, p<0.001) and disease-specific (parent r=-0.53, p=0.005; youth r=-0.53, p<0.001) HRQL. Common parent-reported barriers were youth reliance on parent reminders [42.9%]; adolescent frustration (youth tired of living with SCD [35.7%]); regimen adaptation (hard to stick to a medication schedule [28.6%]); and HU beliefs (parental concern about possible effects of HU on either fertility or effect on fetus [25%]). Common youth barriers were adolescent frustration (tired of living with SCD [57.1%]; forgetfulness about taking HU [53.6%], tired of taking HU [39.3%], not wanting to take HU at school [28.6%], and not wanting to be seen taking HU [25%],); HU ingestion issues (difficulty swallowing HU [25%], taking too many pills [39.3%], dislikes taste [35.7%]; regimen adaptation (not organized regarding taking HU [28.6%]) and knowledge deficits (not understanding how HU works [25%]. Controlling for group assignment and time, parents assigned to the intervention demonstrated a trend in less reported adolescent frustration (p=0.18). For adolescents assigned to the intervention, ingestion-related barriers significantly declined over 6 months (-0.17 per month, p=0.02). Total barriers and other subscale scores did not significantly change over the 6 month period.

Conclusions: HU barriers were frequently reported but differed by parent versus youth perspective. To improve HU adherence in youth with SCD, barriers of both dyad members must be addressed. Greater barriers were associated with poorer total generic and disease-specific HRQL. Controlling for group assignment and time, CHW support helped youth to address HU ingestion barriers. The relationships between perceived barriers, HU adherence and HRQL are complex. Perceived HU barriers may mediate the relationship between an intervention to improve adherence and HRQL. A multi-site trial powered to test these relationships is underway.

References

¹Green et al. (2017) Pediatr Blood Cancer, 64; e26689.https://doi.org/10.1002/pbc.26689

²Smaldone et al. (2018) J Pediatr; 197:177-185.

³Simon, LE, Blount, RL. (2007) J Pediatr Psychol; 32:831-844.

⁴Oyeku et al. (2013) Pediatr Blood Cancer; 60:653-658.

⁵Panepinto et al. (2013) Pediatr Blood Cancer, 60:1338-44.