Hydroxyurea use among children with sickle cell anemia

Patterns of primary and specialty care among children with sickle cell anemia

BACKGROUND AND OBJECTIVE

National guidelines recommend that children with sickle cell anemia (SCA) be seen regularly by primary care providers (PCPs) as well as hematologists to receive comprehensive, multidisciplinary care. The objective is to characterize the patterns of primary and hematology care for children with SCA in Michigan.

METHODS

Using validated claims definitions, children ages 1-17 years with SCA were identified using Michigan Medicaid administrative claims from 2010 to 2018. We calculated the number of outpatient PCP and hematologist visits per person-year, as well as the proportion of children with at least one visit to a PCP, hematologist, or both a PCP and hematologist annually. Negative binomial regression was used to calculate annual rates of visits for each provider type.

RESULTS

A total of 875 children contributed 2889 person-years. Of the total 22,570 outpatient visits, 52% were with a PCP and 34% with a hematologist. Annually, 87%-93% of children had a visit with a PCP, and 63%-85% had a visit with a hematologist. Approximately 66% of total person-years had both visit types within a year. The annual rate ranged from 2.3 to 2.5 for hematologist visits and from 3.7 to 4.1 for PCP visits.

CONCLUSIONS

Substantial gaps exist in the receipt of annual hematology care. Given that the majority of children with SCA see a PCP annually, strategies to leverage primary care visits experienced by this population may be needed to increase receipt of SCA-specific services.

Effects of hydroxyurea on fertility in male and female sickle cell disease patients. A systemic review and meta-analysis

BACKGROUND

Evidence supports the benefits of hydroxyurea (HU) in adults with sickle cell disease (SCD), but reservations remain due to long-term concerns of fertility. Retrospective analysis of clinical records of SCD patients (haemoglobin SS genotype) have identified gender-related differences in disease progression. This could inform risk stratification during SCD at diagnosis with the possibility to guide therapeutic decisions.

METHODS

This systemic review and meta-analysis evaluated fertility parameters in both children (aged ≥ 6 years) and adults with SCD receiving HU therapy. Studies were sourced from PubMed and EMBASE from inception to July 2023. A total of 160 potentially relevant articles were identified.

RESULTS

Four studies were included that evaluated the effects of HU on sperm parameters in males. A further 4 studies assessed anti-mullerian hormone (AMH) levels and ovarian reserves in females. Differences from baseline values were used to identify compromised fertility. Amongst males, HU treatment negatively impacted the concentration of spermatozoa (MD = -15.48 million/mL; 95% CI: [-20.69, -10.26]; p< 0.001), which continued following treatment cessation (MD = -20.09 million/mL; 95% CI: [-38.78, -1.40]; P = 0.04). HU treatment also led to lower total sperm counts (MD = -105.87 million; 95% CI: [-140.61, -71.13]; P< 0.001) which persisted after treatment (MD = -53.05 million; 95% CI: [-104.96, -1.14]; P = 0.05). Sperm volume, initial forward motility and morphology were unaffected by HU treatment. In females, HU treatment decreased the mean AMH levels 1.83 (95% CI [1.42, 2.56]. A total of 18.2.% patients treated with HU showed reduced ovarian reserves.

INTERPRETATION & CONCLUSIONS

This systemic review and meta-analysis suggest that the use of HU for SCD impacts seminal fluid parameters in males and can diminish AMH levels and ovarian reserves in females.

A multilevel mHealth intervention boosts adherence to hydroxyurea in individuals with sickle cell disease

Hydroxyurea reduces sickle cell disease (SCD) complications, but medication adherence is low. We tested 2 mobile health (mHealth) interventions targeting determinants of low adherence among patients (InCharge Health) and low prescribing among providers (HU Toolbox) in a multi-center, non-randomized trial of individuals with SCD ages 15-45. We compared the percentage of days covered (PDC), labs, healthcare utilization, and self-reported pain over 24 weeks of intervention and 12 weeks post-study with a 24-week preintervention interval. We enrolled 293 patients (51% male; median age 27.5 years, 86.8% HbSS/HbSβ0-thalassemia). The mean change in PDC among 235 evaluable subjects increased (39.7% to 56.0%; P < 0.001) and sustained (39.7% to 51.4%, P < 0.001). Mean HbF increased (10.95% to 12.78%; P = 0.03). Self-reported pain frequency reduced (3.54 to 3.35 events/year; P = 0.041). InCharge Health was used ≥1 day by 199 of 235 participants (84.7% implementation; median usage: 17% study days; IQR: 4.8-45.8%). For individuals with ≥1 baseline admission for pain, admissions per 24 weeks declined from baseline through 24 weeks (1.97 to 1.48 events/patient, P = 0.0045) and weeks 25-36 (1.25 events/patient, P = 0.0015). PDC increased with app use (P < 0.001), with the greatest effect in those with private insurance (P = 0.0078), older subjects (P = 0.033), and those with lower pain interference (P = 0.0012). Of the 89 providers (49 hematologists, 36 advanced care providers, 4 unreported), only 11.2% used HU Toolbox ≥1/month on average. This use did not affect change in PDC. Tailoring mHealth solutions to address barriers to hydroxyurea adherence can potentially improve adherence and provide clinical benefits. A definitive randomized study is warranted. This trial was registered at www.clinicaltrials.gov as #NCT04080167.

Adherence to hydroxyurea and clinical outcomes among children with sickle cell anemia

OBJECTIVE

Hydroxyurea lowers the incidence of vaso-occlusive pain crises (VOC) and acute chest syndrome (ACS) among children with sickle cell anemia (SCA). Our objective was to assess the relationship between levels of adherence to hydroxyurea and clinical outcomes among children and adolescents with SCA.

METHODS

This retrospective cohort study included Medicaid data (2005-2012) from Florida, Illinois, Louisiana, Michigan, South Carolina, and Texas. The study population consisted of children 1-17 years old with SCA enrolled in Medicaid for 3 years. Among children that initiated hydroxyurea, the medication possession ratio (MPR) was calculated as the proportion of days covered by hydroxyurea. Six months after initiation of hydroxyurea, clinical outcomes were assessed through the end of the study period: numbers of VOC-related inpatient admissions and emergency department visits, and encounters for ACS. Multivariable Poisson models were used to predict outcomes by MPR quartile adjusting for previous healthcare utilization, state, and age.

RESULTS

Hydroxyurea was initiated by 515 children. The median MPR was 0.53 (interquartile range = 0.3-0.8). The annual median number of visits was 0.0 for ACS, 1.3 for VOC-related emergency department, and 1.4 for VOC-related inpatient admissions. For each outcome, the highest quartile of MPR had the lowest predicted count; this difference was significant for ACS visits when compared with the lowest quartile of MPR.

CONCLUSION

This study demonstrated a high level of adherence (>75%) was essential to achieve a lower incidence of common negative clinical outcomes. Further, moderate and severe hydroxyurea nonadherence may be more common than previously appreciated among children, emphasizing the importance of developing and testing innovative strategies to increase adherence.

Leveraging mathematical modeling to analyze nonadherence for hydroxyurea therapy in sickle cell disease

Nonadherence is common in individuals with sickle cell disease (SCD) on hydroxyurea therapy and can be observed with waning improvements in hematologic parameters or biomarkers like mean cell volume and fetal hemoglobin level over time. We modeled the impact of hydroxyurea nonadherence on longitudinal biomarker profiles. We estimated the potential nonadherent days in individuals exhibiting a drop in biomarker levels by modifying the dosing profile using a probabilistic approach. Incorporating additional nonadherence using our approach besides existing ones in the dosing profile improves the model fits. We also studied how different patterns in adherence give rise to various physiological profiles of biomarkers. The key finding is consecutive days of nonadherence are less favorable than when nonadherence is interspersed. These findings improve our understanding of nonadherence and how appropriate intervention strategies can be applied for individuals with SCD susceptible to the severe impacts of nonadherence.

Trends in blood transfusion, hydroxyurea use, and iron overload among children with sickle cell disease enrolled in Medicaid, 2004-2019

BACKGROUND

There have been significant changes in clinical guidelines for sickle cell disease (SCD) over the past two decades, including updated indications for hydroxyurea, transfusions, and iron overload management. In practice however, there are few studies that examine SCD care utilization over time.

METHODS

We conducted a serial cross-sectional cohort study of pediatric SCD patients from 2004 to 2019 using Georgia Medicaid claims data. For each year, we reported receipt of any transfusion, chronic transfusion, or three or more filled hydroxyurea prescriptions. For children receiving chronic transfusion (six or more annual transfusions), we evaluated iron overload diagnosis, monitoring, and chelation use. Among children with sickle cell anemia (SCA), we examined rates of transfusions and hydroxyurea use. The Cochran-Armitage test was used to assess trend.

RESULTS

There were 5316 unique children 2-18 years old with SCD enrolled in Georgia Medicaid from 2004 to 2019. Children receiving any transfusion increased from 2004 to 2010, then stabilized. In SCA patients, chronic transfusions initially increased from 2004 to 2010, then stabilized from 2010 to 2019. For chronically transfused children, monitoring of iron burden and filled chelator prescriptions both increased significantly. Hydroxyurea use in SCA patients increased from 12% to 37%, with increases noted within each age group, most notably from 21% to 60% in the 13-18-year-old cohort.

CONCLUSION

We demonstrated changes in SCD care utilization over time, including increased hydroxyurea use, changes in transfusion rates, and increased attention to iron overload management. While trends in clinical management do follow updates in treatment guidelines, there is still delayed and suboptimal uptake of guideline recommendations in pediatric SCD patients.

Advanced Clinical Parameters: a complementary hydroxyurea adherence evaluation in sickle cell anemia treatment

OBJECTIVES

Given the complex pathology of sickle cell anemia (SCA) and low adherence to Hydroxyurea (HU) treatment, there is a need to seek parameters that identify recent changes in patient status. The Advanced Clinical Parameters (ACPs) allow an early analysis of hematopoiesis. We aimed to draw the demographic profile of non-adherent SCA patients and to verify the use of ACPs as a measure of HU treatment adherence.

METHOD

In a cross-sectional study, we divided 83 SCA subjects treated with HU into Children (<12 years old) and Adolescents/Adults (≥12 years old). Their haemogram with the ACPs, electronic medical charts and pharmacy claim data were analyzed.

RESULTS

Non-adherent ≥12 years old patients had significantly increased WBC, absolute neutrophil, lymphocyte, monocyte, and basophil counts, RBC, RET, RDW, and PLT, and significantly decreased MCV and MCH. Subjects in the Adolescent/Adult group with IG† ≥0.035 cells/mm³ had the RR for non-adherence increased by 4.6 times (p=0.014), and the systemic immune inflammation index (SII) of non-adherent patients was also significantly higher (p=0.042).

CONCLUSION

IG† presents clinical utility in early identification of non-adherence to HU, especially when combined with other parameters, suggesting the evaluation of ACPs in laboratory routine, as they can be easily implemented. This article is protected by copyright. All rights reserved.

Ten-year Longitudinal Analysis of Hydroxyurea Implementation in a Pediatric Sickle Cell Program

Hydroxyurea (HU) has proven benefit in sickle cell anemia (SCA), but HU is still underutilized. The Pediatric Sickle Cell Program of Northern Virginia prescribes HU regardless of symptoms to all SCA patients age ≥ 9 months and prospectively tracks outcomes. HU is dosed to maximum tolerated dosing (MTD), targeting 30% Hgb F. Longitudinal data from 2009-2019 encompassing 1222 HU-eligible and 950 HU-exposure patient-years were analyzed in 2-year intervals for hemoglobin (Hgb), fetal hemoglobin (Hgb F), hospitalizations, transfusions, and treat-and-release ED visits. Comparing HU-eligible patients in the interval prior to HU implementation (2009-2011) to the last interval analyzed after HU implementation (2017-2019), HU usage increased from 33% to 93%, average Hgb increased from 8.3±0.98 to 9.8±1.3 g/dL (p<0.0001), average Hgb F rose from 13±8.7% to 26±9.9% (p<0.0001), hospitalizations decreased from 0.71 (95% CI 0.54-0.91) to 0.2 (95% CI 0.13-0.28) admissions/person-year, sporadic transfusions decreased from 0.4 (95% CI 0.27-0.55) to 0.05 (95% CI 0.02-0.12) transfusions/person-year. Treat-and-release ED visit rates remained unchanged, varying between 0.49 (95% CI 0.36-0.64) and 0.64 (95% CI 0.48-0.83) visits/person-year. By the last interval, 72% of patients had Hgb ≥ 9g/dL, 42% had Hgb F ≥ 30%, 79% experienced no hospitalizations, and 94% received no transfusions. Uniform HU prescription for SCA patients with close monitoring to achieve high Hgb F resulted in significant improvements in laboratory and clinical outcomes within 2 years, which continued to improve over the next 6 years. Rigorous HU implementation in a pediatric sickle cell population is feasible, effective, and sustainable. This article is protected by copyright. All rights reserved.

Impact of hydroxyurea dose and adherence on hematologic outcomes for children with sickle cell anemia

BACKGROUND

Hydroxyurea is the primary treatment for sickle cell anemia (SCA), yet real-world implementation in high-income settings is suboptimal. Variation in prescribed hydroxyurea dose and patient adherence in these settings can both affect actual exposure to hydroxyurea. Quantifying the contributions of hydroxyurea dose and medication adherence to the relationship between hydroxyurea exposure and hematologic parameters could inform strategies to optimize exposure and improve outcomes.

PROCEDURE

We evaluated the relationship between hydroxyurea exposure, defined by average prescribed dose and adherence, and hematologic parameters using data from children with SCA who were enrolled in two prospective hydroxyurea adherence studies. Hydroxyurea adherence was assessed by video directly observed therapy or electronic pill bottle and medication administration record. Average prescribed dose was abstracted from prescriptions in patients' electronic medical record. Participants with a hydroxyurea exposure >20 mg/kg/day and ≤20 mg/kg/day were included in the higher and lower exposure groups, respectively.

RESULTS

Forty-five participants were included in the analysis (56% male; median age 12 years [range 2-19]; 98% Black). Higher exposed participants (n = 23) were prescribed a higher dose (27.2 vs. 24.4 mg/kg/day, p = .002) and had better adherence (0.92 vs. 0.71, p ≤ .001) compared to lower exposed participants (n = 22). Higher exposure was associated with higher fetal hemoglobin (p = .04) and mean corpuscular volume (p = .02).

CONCLUSIONS

Higher hydroxyurea exposure is associated with improved hematologic parameters in the high-income setting and is affected by both prescribed dose and adherence. Future studies are needed to optimize both adherence and hydroxyurea prescribing and confirm that increasing exposure improves clinical outcomes in this setting.

Improving Preventive Care for Children With Sickle Cell Anemia: A Quality Improvement Initiative

Sickle cell disease is a complex chronic disorder associated with increased morbidity and early mortality. The Pediatric Quality Measures Program has developed new sickle cell-specific quality measures focused on hydroxyurea (HU) counseling and annual transcranial Doppler (TCD) screening; however, these measures have not been used in a clinical setting to inform quality improvement (QI) efforts.

METHODS

From 2017 to 2018, 9 sickle cell subspecialty clinics from the Pacific Sickle Cell Regional Collaborative conducted a year-long QI collaborative focused on improving the percentage of patients with HU counseling and TCD screening based on the new quality measures. After an initial kick-off meeting, the 9 sites participated in monthly conference calls. We used run charts annotated with plan-do-study-act cycle activities to track each site's monthly progress and the overall mean percentage for the entire collaborative.

RESULTS

There was an overall improvement in the aggregate HU counseling from 85% to 98% (P < 0.01). For TCD screening, referral frequency changed from 85% to 90% (P = 0.76). For both measures, the variation in frequencies decreased over the year.

CONCLUSION

Over 1 year, we found that a regional QI collaborative increased HU counseling. Although referral for TCD screening increased, there was no overall change in TCD completion. Overall, this QI report's findings can help clinicians adopt and implement these quality measures to improve outcomes in children.

Splenic function is not maintained long-term after partial splenectomy in children with sickle cell disease

BACKGROUND

Partial splenectomy (PS) may allow preservation of splenic function in cases where splenectomy is indicated for hematologic diseases; however, the long-term outcomes are uncertain. We investigated the long-term outcomes of PS in patients with sickle cell disease (SCD).

METHODS

A single-institution retrospective chart review was performed for children with SCD who underwent PS from 1997 to 2017. For comparison, we reviewed outcomes for patients who underwent PS for hereditary spherocytosis (HS). The primary endpoint was viability of the splenic remnant as inferred by the presence of remnant perfusion on ultrasound and/or liver spleen scan.

RESULTS

Nine patients with SCD and 26 patients with HS underwent PS at a median age of 11 (IQR, 9-14) and 7.5 (IQR, 6-13) years, respectively. All underwent laparoscopic PS with three (7.9%) conversions to open. Two SCD patients were lost to long-term follow-up. The remaining seven SCD patients had initial postoperative splenic remnant perfusion demonstrated by ultrasonography. By 42 months postoperatively, however, none had a functioning splenic remnant. The median time to loss of splenic remnant was 12.6 (IQR 9.2-28.5) months. In contrast, all HS patients demonstrated robust splenic remnant blood flow with a median follow-up of 46 (IQR 37-82) months.

CONCLUSION

No patient with SCD who underwent PS had viable splenic tissue for more than 42 months, likely due to continued autoinfarction typical of patients with this disease. Therefore, we believe that PS to preserve splenic function is not indicated in patients with SCD.

LEVEL OF EVIDENCE

III.

Integration of Mobile Health Into Sickle Cell Disease Care to Increase Hydroxyurea Utilization: Protocol for an Efficacy and Implementation Study

BACKGROUND

Hydroxyurea prevents disease complications among patients with sickle cell disease (SCD). Although its efficacy has been endorsed by the National Health Lung and Blood Institute evidence-based guidelines, its adoption is low, both by patients with SCD and providers. Mobile health (mHealth) apps provide benefits in improving medication adherence and self-efficacy among patients with chronic diseases and have facilitated prescription among medical providers. However, mHealth has not been systematically tested as a tool to increase hydroxyurea adherence nor has the combination of mHealth been assessed at both patient and provider levels to increase hydroxyurea utilization.

OBJECTIVE

This study aims to increase hydroxyurea utilization through a combined two-level mHealth intervention for both patients with SCD and their providers with the goals of increasing adherence to hydroxyurea among patients and improve hydroxyurea prescribing behavior among providers.

METHODS

We will test the efficacy of 2 mHealth interventions to increase both patient and provider utilization and knowledge of hydroxyurea in 8 clinical sites of the NHLBI-funded Sickle Cell Disease Implementation Consortium (SCDIC). The patient mHealth intervention, InCharge Health, includes multiple components that address memory, motivation, and knowledge barriers to hydroxyurea use. The provider mHealth intervention, Hydroxyurea Toolbox (HU Toolbox), addresses the clinical knowledge barriers in prescribing and monitoring hydroxyurea. The primary hypothesis is that among adolescents and adults with SCD, adherence to hydroxyurea, as measured by the proportion of days covered (the ratio of the number of days the patient is covered by the medication to the number of days in the treatment period), will increase by at least 20% after 24 weeks of receiving the InCharge Health app, compared with their adherence at baseline. As secondary objectives, we will (1) examine the change in health-related quality of life, acute disease complications, perceived health literacy, and perceived self-efficacy in taking hydroxyurea among patients who use InCharge Health and (2) examine potential increases in the awareness of hydroxyurea benefits and risks, appropriate prescribing, and perceived self-efficacy to correctly administer hydroxyurea therapy among SCD providers between baseline and 9 months of using the HU Toolbox app. We will measure the reach, adoption, implementation, and maintenance of both the InCharge Health and the HU Toolbox apps using the reach, effectiveness, adoption, implementation, and maintenance framework and qualitatively evaluate the implementation of both mHealth interventions.

RESULTS

The study is currently enrolling study participants. Recruitment is anticipated to be completed by mid-2021.

CONCLUSIONS

If this two-level intervention, that is, the combined use of InCharge Health and HU Toolbox apps, demonstrates efficacy in increasing adherence to hydroxyurea and prescribing behavior in patients with SCD and their providers, respectively, both apps will be offered to other institutions outside the SCDIC through a future large-scale implementation-effectiveness study.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04080167; https://clinicaltrials.gov/ct2/show/NCT04080167.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/16319.

Systematic Review of Crizanlizumab: A New Parenteral Option to Reduce Vaso-occlusive Pain Crises in Patients with Sickle Cell Disease

Hydroxyurea, indicated for managing sickle cell anemia (SCA), and L-glutamine, indicated for treating sickle cell disease (SCD), were the only pharmacotherapeutic options in this patient population before the approval of crizanlizumab by the U.S. Food and Drug Administration in November 2019 to reduce vaso-occlusive crisis (VOC) frequency. This article reviews the evidence pertaining to crizanlizumab in SCD by searching records in Medline, Embase, and International Pharmaceutical Abstracts. Crizanlizumab, a P-selectin inhibitor, mitigates the microvascular vaso-occlusion in SCD. In the multicenter randomized double-blind SUSTAIN trial, a higher dose of crizanlizumab decreased the incidence of VOCs by 45% and prolonged the median time to the first and second VOC. A post hoc subgroup analysis demonstrated that the proportion of patients who had no VOC incidence during the study period was greater in the crizanlizumab group, and this benefit was consistent regardless of concomitant hydroxyurea use, prior categorized history of VOC frequency, or SCD genotype. Crizanlizumab had a safety profile comparable with placebo. Multiple ongoing clinical trials are trying to establish its roles in pediatric patients with SCD and its effects on alleviating other SCD-related complications. As the first parenteral option for SCD, providers need to formulate administration logistics to improve patients' access to crizanlizumab. Current available data suggest crizanlizumab is a promising agent to reduce VOC in patients with SCD.

Pediatric Orphan Drug Indications: 2010-2018

BACKGROUND

Orphan drug development is crucial for children, who are disproportionately affected by rare diseases. Data are lacking on the number, nature, and benefit of recently approved pediatric orphan indications.

METHODS

We classified the 402 orphan indications the US Food and Drug Administration approved between 2010 and 2018 as "pediatric" if they were approved for children only or targeted pediatric diseases. We determined the number of unique diseases targeted by pediatric orphan indications and calculated the proportion that were for (1) novel drugs, (2) non-novel drugs approved to treat ≥1 common disease, and (3) non-novel drugs approved only to treat rare diseases. Among pediatric orphan indications eligible for US Food and Drug Administration breakthrough designation (granted to drugs potentially representing major therapeutic advances), we calculated the proportion receiving this designation.

RESULTS

Of the 402 orphan indications, 136 (33.8%) were pediatric. These 136 indications targeted 87 unique diseases; 21 diseases were targeted by ≥1 indication. Of the 136 pediatric orphan indications, 60 (44.1%) were for novel drugs, 45 (33.1%) were for non-novel drugs approved to treat ≥1 common disease, and 31 (22.8%) were for non-novel drugs approved only to treat rare diseases. Among 97 indications eligible for breakthrough designation, 20 (20.6%) received this designation.

CONCLUSIONS

Recent orphan drug development has increased the availability of treatments for pediatric rare diseases. Most pediatric orphan indications expanded use of existing drugs, and many targeted the same disease. Some indications may represent breakthroughs, but substantial unmet need for treatments remains for most pediatric rare diseases.

HABIT efficacy and sustainability trial, a multi-center randomized controlled trial to improve hydroxyurea adherence in youth with sickle cell disease: a study protocol

Background

Hydroxyurea (HU) is recommended as standard practice for youth with sickle cell disease (SCD). Yet, despite its efficacy, HU adherence in adolescents and young adults is often poor. Poor medication adherence increases disease burden, healthcare cost and widens health disparities. Adolescence is a critical time to improve adherence through improved chronic disease self-management. This study aims to test the efficacy of an intervention delivered to youth/parent dyads by community health workers (CHWs), augmented by tailored text messages on HU adherence (primary outcome). Secondary outcomes are intervention sustainability, youth health-related quality of life, self-management responsibility concordance, acute hospital use and self-reported disease symptoms.

Methods

Hydroxyurea Adherence for Personal Best in Sickle Cell Disease, “HABIT,” is a 12 month multi-center randomized controlled trial. One hundred four youth, 10 to 18 years of age prescribed HU who meet eligibility criteria, enrolled with their parent as dyads, will be randomized 1:1 to either the HABIT intervention or to usual clinical care plus education handouts. All subjects will complete clinic visits at months 0, 2, 4, 6 (efficacy component), 9 and 12 (sustainability component) for assessment of HbF biomarker, other hematologic parameters, and to complete questionnaires. In addition, dyads assigned to the HABIT intervention will work with CHWs to identify a daily habit (e.g., brushing teeth) on which to build a HU adherence habit. Tailored daily text message reminders to support the habit will be developed by the dyad in collaboration with the CHWs and sent to parent and youth. At the 6 month visit, the intervention will end and the sustainability portion of the trial will begin. All data analyses will be based on intention to treat with all randomized subjects included in the analyses.

Discussion

Prior retrospective studies demonstrate that a majority of adolescents are poorly adherent to HU. If efficacious, the HABIT intervention has the potential to improve the lives of youth with SCD.

Trial registration

Clinicaltrials.gov NCT03462511. Registered March 6, 2018, last updated July 26, 2019.