Youth diagnosed with sickle cell disease (SCD) may have difficulty taking medication as prescribed (adherence). Hydroxyurea (HU) is one medication that youth may take to help manage SCD. Electronic adherence monitoring is widely considered the gold standard in objective adherence measurement. These monitors provide continuous, real-time records of medication adherence and reveal problematic behavior patterns, including underdosing, overdosing, delayed dosing, "drug holidays" (i.e. where individuals do not take medications for a specified interval of time), and "white coat" adherence (i.e., a pattern of drug adherence as a function of time where individuals display good adherence immediately before and after clinic attendance with worsening adherence in the period between).

Overall, electronic adherence measures are considered valid, reliable, and accurate, with clear advantages over pharmacy refill records, physician estimates and self-report measures. Currently, only one electronic measure capable of monitoring medications in both pill and liquid form is being manufactured: WisePill and WiseBag. While data are limited regarding its validity and reliability, preliminary data support the use of Wise technology to measure adherence to medication. The current study will determine the Wise device's ability to feasibly measure adherence to liquid and solid form HU medication in a pediatric SCD population.

This research study will evaluate HU adherence using an electronic storage device (Wise device) compared to caregiver report, youth report, lab values, and pill-count adherence measures. The investigators will ask participants to store their medication in the Wise device and answer questions about their use of the device during normal clinical care visits.

PRIMARY OBJECTIVE

• To examine feasibility of the WISE device by estimating a) rate of consent to the study, b) rate of WISE device use, c) rate of WISE device failure, and d) the perceived acceptability of using the WISE device, as reported by caregivers and youth.

SECONDARY OBJECTIVE

• To estimate the association between HU adherence as measured by the Wise device, to a) caregiver-report, b) youth-report, c) lab values, d) pill-count, and e) Medication Possession Ratio (MPR) adherence measures.

Evaluation of study outcomes will be stratified by age group: (1) infants/toddlers, ages 0-7 years; (2) school age, ages 8-12 years; and (3) teen, ages 13-17 years.

At study enrollment, participants will be asked to complete one questionnaire and will receive instructions on how to use the Wise device. They will be asked to use the Wise device over the following two months. A study team member will contact each participant by phone within seven days of study enrollment to monitor participant use of the Wise device and to answer any questions. Participants will be asked to return the Wise device in two months at their normal clinic care visit. At this visit, participants will be asked to complete two more questionnaires and, as part of standard clinical care, a pill count/bottle weight will be completed by the pharmacy.

Inclusion Criteria:

• Confirmed diagnosis of SCD (any genotype).
• Less than 18 years of age at time of study entry.
• Currently followed in the St. Jude Children's Research Hospital (SJCRH) SCD clinic.
• Stable HU dose prescribed (in pill or liquid formulation) for ≥ 6 months without documented hematological toxicity (excluding dose adjustments for weight gain).
• Lives with their primary caregiver.
• Anticipated to return to clinic at proposed 4-week or 8-week intervals.

Exclusion Criteria:

• Primary caregiver and/or youth unable to understand English and/or youth not cognitively intact (known IQ < 70) such that the study questionnaire cannot be understood and completed.
• Any condition or chronic illness that in the opinion of the PI or Co-I makes participation on the study ill-advised.

Participants will have a diagnosis of sickle cell disease,be receiving treatment with hydroxyurea, and meet eligibility criteria.