Hydroxycarbamide adherence and cumulative dose associated with hospital readmission in sickle cell disease: a 6-year population-based cohort study

Prevalence and cost of sickle cell disease in France: real-world analysis using data from the Echantillon Généraliste des Bénéficiaires

Sickle cell disease (SCD) is a genetic disorder of the hemoglobin resulting in chronic anemia, hemolysis, and vaso-occlusions. Its treatment mostly relies on hydroxycarbamide, transfusions, and stem cell transplantation. This study aimed at describing the epidemiology and management of SCD in adolescent and adult patients in France. This was a retrospective study performed among SCD patients aged ≥12 years between 2016 and 2018 and controls. SCD patients were matched on a 1:3 ratio with a group of individuals with no diagnosis of SCD, referred as control group. The matching of SCD patients and controls was a direct matching based on age, sex, CMU-c status (which corresponds to free-of-charge complementary coverage for people with low resources) and geographical region of residence. SCD patients and their matched controls were followed-up for the same amount of time by adjusting controls' follow-up period to that of the associated patients. This study used claims data from the French representative 1/97th sample of health data system. The main outcomes were the patients' characteristics and treatments received, healthcare consumptions and related costs among SCD cases and controls. Between 2016 and 2018, 151 patients with ≥6 months of follow-up were identified out of the total population of 732,164 individuals. SCD prevalence extrapolated to the entire population [95% CI] was 19,502 [19,230, 19,778] in 2018. The median (Q1-Q3) age at inclusion date was 37.0 (25.0-48.0) years, with 69.5% of patients being female. The mean (SD) reimbursed cost over follow-up was €24,310 (89,167), mostly represented by hospitalization costs accounting for €21,156 (86,402). A switch in SCD management was observed with age, as younger patients presented more frequent hospitalizations and acute procedures, while older ones had more frequent medical visits and paramedical care. Mean (SD) annual costs were €25,680 (91,843) and vs. €3,227 (23,372) for patients and controls, respectively (p < 0.001), representing an extra cost of almost €150 million over the entire SCD population. This study highlighted the important costs related to SCD and the related medical need with treatment alternatives, which could be filled by the emergence of new therapies.

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.

Impact of adherence to hydroxyurea on health outcomes among patients with sickle cell disease

Although new pharmaceutical therapy options have recently become available, hydroxyurea is still the most commonly used and affordable treatment option for sickle cell disease (SCD). This study aimed to update the evidence on hydroxyurea adherence and its association with clinical and economic outcomes among individuals with SCD. This retrospective study used Texas Medicaid claims data from 09/2011-08/2016. Individuals were included if they had ≥1 inpatient or ≥2 outpatient SCD diagnoses, had ≥1 hydroxyurea prescription, were 2-63 years of age, and were continuously enrolled in Texas Medicaid between 6 months before and 1 year after the first hydroxyurea prescription fill date (index date). Hydroxyurea adherence (Medication Possession Ratio; MPR), vaso-occlusive crisis (VOC)-related outcomes, healthcare utilization and expenditures (SCD-related and all-cause) during the 1 year following the index date were measured. Bivariate and multivariable analyses were used to address the study objectives. Among 1035 included individuals (age: 18.8 ± 12.5 years, female: 52.1%), 20.9% were adherent to hydroxyurea (defined as MPR≥0.8). After adjustment for demographic and clinical characteristics, compared to being non-adherent, adhering to hydroxyurea was significantly associated with: a lower risk (Odds Ratio [OR] = 0.480, p = .0007) and hazard rate (Hazard Ratio [HR] = 0.748, p = .0005) of a VOC event, fewer VOC events (Incidence Rate Ratio [IRR] = 0.767, p = .0009), fewer VOC-related hospital days (IRR = 0.593, p = .0003), fewer all-cause and SCD-related hospitalizations (IRR = 0.712, p = .0008; IRR = 0.707, p = .0008, respectively) and emergency department visits (IRR = 0.768, p = .0037; IRR = 0.746, p = .0041, respectively), and lower SCD-related total healthcare expenditures (IRR = 0.796, p = .0266). Efforts to increase adherence to hydroxyurea could improve clinical and economic outcomes among individuals with SCD.

Treatment patterns and burden of complications associated with sickle cell disease: A US retrospective claims analysis

Complications associated with sickle cell disease (SCD) that are highly impactful for patients but until recently have been less understood include priapism, nephropathy, and neurologic injury. We conducted a retrospective study using US administrative claims data from July 01, 2013 through March 31, 2020 to analyze incidence of these complications, SCD treatment patterns, and healthcare resource utilization (HCRU) and costs among 2524 pediatric and adult patients with SCD (mean [SD] age 43.4 [22.4] years). The most common treatments during follow-up were short-acting opioids (54.0% of patients), red blood cell transfusion (15.9%), and hydroxyurea (11.0%). SCD complications occurred frequently; in the overall population, the highest follow-up incidences per 1000 person-years were for acute kidney injury (53.1), chronic kidney disease (40.6), and stroke (39.0). Complications occurred across all age groups but increased in frequency with age; notably, acute kidney injury was 69.7 times more frequent among ages 65+ than ages 0-15 (p < 0.001). Follow-up per-patient-per-month HCRU also increased with age; however, all-cause healthcare costs were similarly high for all age groups and were driven primarily by inpatient stays. Patients with SCD across the age spectrum have a high burden of complications with the use of current treatments, suggesting unmet needs for treatment management.

Medical and Non-medical Costs of Sickle Cell Disease and Treatments from a US Perspective: A Systematic Review and Landscape Analysis

BACKGROUND

Sickle cell disease (SCD) is a complex genetic disorder that manifests in infancy and progresses throughout life in the form of acute and chronic complications. As the upfront costs of potentially curative, genetic therapies will likely be high, an assessment and comprehensive characterization of the medical and non-medical cost burden will inform future decision making.

OBJECTIVE

We sought to systematically summarize the existing literature surrounding SCD medical and non-medical costs.

METHODS

We searched MEDLINE and EMBASE (2008-2020) and identified US-based studies that detailed medical or non-medical costs. Eligible studies provided empirical estimates about any aspect of cost or SCD individuals of all ages and their caregivers. Study quality was assessed using the Newcastle-Ottawa Scale, and costs were adjusted to 2019 US$.

RESULTS

Search queries returned 479 studies, with 342 from medical burden searches and 137 from non-medical burden searches, respectively. Herein, we report the results of the 40 studies that contained relevant cost information: 39 detailed medical costs and 1 detailed non-medical costs. Costs were higher for SCD patients when compared with non-SCD individuals (cost difference range: $6636-$63,436 annually). The highest medical cost component for SCD patients was inpatient ($11,978-$59,851 annually), followed by outpatient and then pharmacy. No studies characterized the cost burden throughout the lifetime disease trajectory of an SCD individual, and no studies captured caregiver or productivity costs.

CONCLUSION

Our results reveal an incomplete characterization of medical and non-medical costs within SCD. A deeper understanding of the medical and non-medical cost burden requires completion of additional studies that capture the burden across the patient's lifetime, in addition to expression of the impact of existing and emergent health technologies on disease trajectory.

Administrative data identify sickle cell disease: A critical review of approaches in U.S. health services research

To identify people living with sickle cell disease (SCD) and study their healthcare utilization, researchers can either use clinical records linked to administrative data or use billing diagnosis codes in stand-alone administrative databases. Correct identification of individuals clinically managed for SCD using diagnosis codes in claims databases is limited by the accuracy of billing codes in outpatient encounters. In this critical review, we assess the strengths and limitations of claims-based SCD case-finding algorithms in stand-alone administrative databases that contain both inpatient and outpatient records. Validation studies conducted using clinical records and newborn screening for confirmation of SCD case status have found that algorithms that require three or more nonpharmacy claims or one inpatient claim plus two or more outpatient claims with SCD codes show acceptable accuracy (positive predictive value and sensitivity) in children and adolescents. Future studies might seek to assess the accuracy of case-finding algorithms over the lifespan.

The association between hydroxyurea adherence and opioid utilization among Texas Medicaid enrollees with sickle cell disease

BACKGROUND: Individuals with sickle cell disease (SCD) suffer from recurrent catastrophic pain crises that are often managed by opioid analgesics. Being adherent to hydroxyurea has been associated with decreased health care resource use for pain; however, evidence of its association with opioid use is limited. OBJECTIVE: To determine if adherence to hydroxyurea is associated with opioid use among patients with SCD. METHODS: This retrospective study used Texas Medicaid data from September 1, 2011, to August 31, 2016 (study period). The index date was the date of hydroxyurea initiation. Patients who were aged 2-63 years at the index date, had ≥ 1 inpatient or ≥ 2 outpatient SCD diagnoses during the study period, had ≥ 1 hydroxyurea prescription during the identification period (September 1, 2011-August 31, 2015), had no diagnosis of other indications for hydroxyurea during the study period, and were continuously enrolled for at least 12 months after the index date were included. Hydroxyurea adherence was measured using medication possession ratio (MPR). The study outcomes (measured 1-year post-index) were (a) opioid use; (b) number of opioid prescriptions; (c) strong opioid use (morphine, hydromorphone, fentanyl, and methadone); (d) number of strong opioid prescriptions; (e) high-dose opioid use (≥ 50 mg morphine milligram equivalent [MME]); and (f) days supply for opioid prescriptions. Covariates included demographic (age and gender) and clinical (vaso-occlusive crisis [VOC], avascular necrosis, iron overload, acute chest syndrome, and blood transfusion) characteristics. Descriptive, bivariate (chi-square and Wilcoxon-Mann-Whitney tests), multiple logistic regression, and negative binomial regression analyses were performed. RESULTS: 1,146 patients (18.3 [12.3] years) met the inclusion criteria. Of these, 19.6% were adherent to hydroxyurea (defined as MPR ≥ 80%) and mean (SD) MPR was 48.3% (29.7%). In the 1 year following hydroxyurea initiation, 923 (80.5%) patients had ≥ 1 opioid prescription with 7.6 (9.4) opioid prescriptions per patient, while 259 (22.6%) patients had ≥ 1 strong opioid prescription with 1.5 (4.4) strong opioid prescriptions per patient. Average (SD) opioid dose was 41.7 (74.3) mg MME, and 27.1% had high daily MME doses (≥ 50 mg MME). Average (SD) opioid days supply was 83.1 (112.2) days. After adjusting for covariates, compared with being nonadherent, being adherent to hydroxyurea was associated with a 50.5% decreased risk of having strong opioids (OR = 0.495, 95% CI = 0.278-0.879, P = 0.0165). Additionally, SCD-related complications (VOC, avascular necrosis, and iron overload) and older age were significant factors associated with opioid use and higher MME. Post hoc analyses showed that being adherent to hydroxyurea was significantly associated with lower probabilities of experiencing SCD-related complications. CONCLUSIONS: Results showed that patients with SCD are moderately adherent to hydroxyurea. Being adherent to hydroxyurea was found to be associated with a lower risk of receiving a prescription for strong opioids. Findings suggest that close monitoring and interventions to improve adherence may help mitigate strong opioid use among these patients. DISCLOSURES: This research did not receive any specific funding. Barner and Kang report grants from Novartis Pharmaceuticals, unrelated to this work. A part of this study was presented as a poster at the American Pharmacists Association (APhA) 2019 Annual Meeting and Exposition (March 22-25, 2019, Seattle, WA) and received the 2019 APhA-APRS Presentation Award in the APhA-APRS Contributed Research Paper, Graduate Student/Fellow/Postdoctoral Scholar category.

Patient-Reported Outcomes and Economic Burden of Adults with Sickle Cell Disease in the United States: A Systematic Review

Purpose

To systematically estimate the patient-reported outcomes (PROs) and economic burden of sickle cell disease (SCD) among adults in the United States (US).

Patients and Methods

Two systematic literature reviews (SLRs), one each for the PROs and economic topics, were performed using MEDLINE and Embase to identify observational studies of adults with SCD. Included studies were published between 2007 and 2018 and evaluated health-related quality of life (HRQL), function, healthcare resource utilization (HCRU), or costs. Given the high degree of clinical and methodological heterogeneity, findings were summarized qualitatively.

Results

The SLRs identified 7 studies evaluating the PROs and 15 studies evaluating the economic burden meeting the pre-specified selection criteria. The PRO evidence showed the prevalence of depression and anxiety to be 21–33% and 7–36%, respectively, in adults with SCD. The mean SF-36 physical summary scores ranged from 33.6 to 59.0 and from 46.3 to 61.5 for the mental summary scores. Overall HRQL for adults with SCD was poor and significantly worse in those with opioid use. Adult SCD patients were found to have varying rates of emergency department (ED) utilization (0.3–3.5 annual ED visits), hospitalizations (0.5–27.9 per patient per year), and/or readmission (12–41%). Key factors associated with significant HCRU were age, dental infection, and SCD-related complications. SCD specialized care settings and SCD intensive management strategy were reported to significantly decrease the number of hospitalizations.

Conclusion

This systematic evidence synthesis found that disease burden measured by PROs and economic burden of SCD on adults in the US are substantial despite the availability of approved SCD treatments during 2007–2018. The use of hydroxyurea, optimal management with opioids, and employing intensive treatment strategies may help decrease the overall burden to patients and healthcare systems. Published data on costs associated with SCD are limited and highlight the need for more economic studies to characterize the full burden of the disease.

Measuring hydroxyurea adherence by pharmacy and laboratory data compared with video observation in children with sickle cell disease

BACKGROUND

Hydroxyurea nonadherence is common among children with sickle cell disease (SCD), but it is unclear if current adherence measures are valid compared with video directly observed therapy (VDOT), a reference method. The objectives were to evaluate if hydroxyurea adherence by pharmacy records, urine assay, mean corpuscular volume (MCV), and/or fetal hemoglobin (HbF) correlated with and was sensitive and specific compared with VDOT.

METHODS

This was a cross-sectional analysis of adherence data from 34 children with SCD on a single-arm, six-month hydroxyurea adherence study. Spearman correlation coefficient compared participants' adherence by pharmacy records, MCV, and HbF to adherence by VDOT. The sensitivity and specificity of ≥80% adherence by pharmacy records, two urine samples with hydroxyurea, MCV ≥100 fl/L, and HbF ≥20% compared with ≥80% VDOT adherence were also calculated.

RESULTS

Median pharmacy and VDOT adherence rates were similar (87.8% vs 88.1%, P = 0.75) and mildly correlated (r_s  = 0.45; P = 0.008) but the sensitivity of ≥80% adherence by pharmacy records was 72.7% and specificity was 45.5%. MCV (r_s  = -0.02, P = 0.92) and HbF (r_s  = -0.2, P = 0.33) did not significantly correlate with VDOT adherence. Sensitivity and specificity were 83.3% and 33.3% for having two urine samples with hydroxyurea, 35% and 71.4% for MCV ≥100 fl/L, and 75% and 0% for HbF ≥20%, respectively.

CONCLUSIONS

Commonly used tools to measure hydroxyurea adherence may not correlate with or be valid compared with video adherence. Future studies to refine these measures are needed to effectively target adherence interventions to children with SCD who have the potential to benefit. (ClinicalTrials.gov NCT02578017).

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.

Inpatient Ordering of Home Hydroxyurea by Residents for Hospitalized Patients With Sickle Cell Disease

BACKGROUND

Hydroxyurea is a well-established disease-modifying medication for sickle cell disease (SCD). At some institutions, hydroxyurea can only be ordered by "chemotherapy-certified" providers which may not include pediatric resident physicians.

METHODS

We conducted a survey of 39 American pediatric hospitals regarding their policy on resident hydroxyurea ordering for SCD. Our institution changed its policy in June 2016 to allow residents to order hydroxyurea for hospitalized patients with SCD who were already on hydroxyurea at home. We conducted a retrospective review of the medical records of a random sample of patients with SCD on hydroxyurea admitted the year before and the year after this policy change.

RESULTS

In our national survey, 51% of surveyed hospitals allowed residents to order hydroxyurea, 19% required a second signature, and 30% did not allow residents to order hydroxyurea. In our institutional study, patients after the policy change were significantly more likely to have received their home hydroxyurea by hospital day 1: before 62/90 (69%) versus after 105/119 (88%), P=0.0005. The proportion of patients who inappropriately received hydroxyurea was very low in both groups: before 1/91 (1%) versus after 3/126 (2%), P=0.64, with no serious adverse clinical events due to inappropriate hydroxyurea administration.

CONCLUSIONS

Considerable national variation in practice currently exists in regards to resident hydroxyurea ordering hospital policies. A policy allowing residents to order hydroxyurea significantly increased the likelihood of a patient receiving hydroxyurea while hospitalized with no significant increase in inappropriate hydroxyurea administration. Resident hydroxyurea ordering seems safe and beneficial.

Increased acute care utilization in a prospective cohort of adults with sickle cell disease

The ESCAPED (Examining Sickle Cell Acute Pain in the Emergency vs Day Hospital) trial is an ongoing prospective study comparing outcomes of people with sickle cell disease (SCD) seeking care for acute pain management in either an emergency department or specialty infusion clinic. The objective of this paper is to describe the baseline characteristics and health care utilization of patients in the trial. This is a multicenter study across 4 US cities that enrolled all adults with SCD living within 60 miles (96.6 km) of a study site who were expected to have acute care utilization over the study period. Twenty-one percent of participants had no acute care visits in the first 12 months of follow-up. Using negative binomial regression, we describe subject characteristics that predict acute care utilization. Three hundred ninety-one subjects have completed 12 months of follow-up with a mean age of 34.5 years (standard deviation, 11.4), 60% are female. Fifty-four percent of subjects with hemoglobin SS disease and 46% with hemoglobin SC disease had 3 or more acute visits over the study period. The prevalence of chronic pain in this cohort was 68%. Predictors of higher rates of acute care utilization included being unemployed, having chronic pain, being on chronic transfusion therapy, having a history of stroke, and being on disability or on Medicaid. This is the first prospective cohort in the modern era, and it demonstrates much higher rates of acute care utilization than reported in the Cooperative Study of Sickle Cell Disease.

A Multidimensional Electronic Hydroxyurea Adherence Intervention for Children With Sickle Cell Disease: Single-Arm Before-After Study

Background

Hydroxyurea is a disease-modifying medication for patients with sickle cell disease (SCD). Despite demonstrated efficacy, hydroxyurea nonadherence in clinical practice is common and results in worse health outcomes for nonadherent patients. Mobile Directly Observed Therapy (Mobile DOT) is a pilot-tested, electronic, multidimensional hydroxyurea adherence intervention for children with SCD. Mobile DOT includes sending daily text message reminders to patients to take hydroxyurea, patients recording and sending daily videos that capture their hydroxyurea administrations for the research team to review and track adherence, providing personalized feedback to patients about their adherence, and providing small monetary incentives to patients if they achieve high hydroxyurea adherence.

Objective

This study aimed to determine if Mobile DOT increases hydroxyurea adherence in children with SCD and to explore its impact on hematologic and clinical outcomes.

Methods

This was a single-arm, 6-month intervention study of patients with SCD on hydroxyurea who were aged ≤19 years and reported having access to an electronic device. Participants’ hydroxyurea adherence when they received Mobile DOT was compared with their adherence 6 months before and after receiving Mobile DOT. Participants’ medication possession ratio (MPR) was calculated from their pharmacy dispensing records and was used to measure adherence. Laboratory and clinical outcomes were abstracted from participants’ electronic medical records. Infrequently hospitalized patients who received at least 160 days of the intervention were considered to be engaged participants.

Results

Of 91 patients who were approached, 55 enrolled and 34 engaged with Mobile DOT. The median age of the engaged participants was 10 years (range 2-18.8 years), and 21 (62%, 21/34) participants were male, 28 (82%, 21/34) had hemoglobin SS SCD, and 19 (56%, 19/34) were prescribed hydroxyurea for at least a year before enrollment. With Mobile DOT, engaged participants’ median MPR increased from 61.7% to 84.4% (P<.001) and significantly more (67% vs 30%; P=.002) achieved ≥80% hydroxyurea adherence compared with baseline values. Engaged participants’ mean fetal hemoglobin (HgbF) levels and mean corpuscular volumes (MCV) improved significantly after 6 months of Mobile DOT (P=.04 and P=.001, respectively), but their adherence, HgbF levels, and MCV returned to baseline values during the 6 months after the intervention. Hospitalizations and the clinical outcomes that were measured occurred infrequently during the study. Nonengagement was associated with being female and having a recent SCD complication. In addition, having insufficient electronic data, being unable to quickly complete Mobile DOT each day, and not perceiving that Mobile DOT was beneficial may have further decreased engagement.

Conclusions

Mobile DOT shows promise as an effective intervention for some children with SCD. Modifications that may improve recruitment, reduce attrition, and increase engagement were identified and could increase the impact that Mobile DOT has on children with SCD.

Trial Registration

ClinicalTrials.gov NCT02578017; https://clinicaltrials.gov/ct2/show/NCT02578017

Beta2-Adrenergic Receptor Polymorphisms and Haplotypes Associate With Chronic Pain in Sickle Cell Disease

Pain in sickle cell disease (SCD) is severe, variable, and inadequately comprehended. The β2-adrenergic receptor (ADRB2) is critical in mediating neurotransmitter response in the sympathetic nervous system. In this association study, we examined 16 single nucleotide polymorphisms (SNPs) covering 5'-UTR and coding regions of ADRB2 for pain variability in SCD. Subjects recorded their non-crisis, baseline pain experience on a computerized tool from which we obtained chronic pain measurement score- composite pain index (CPI). Regression models yielded significant associations between chronic pain and seven SNPs. Non-synonymous SNP rs1042713 A allele (Arg16) caused a 5.73-fold decrease in CPI (p = 0.002). Allele A of rs12654778 and T of rs17778257 reduced CPI by a fold of 4.52 (p = 0.019), and 4.39 (p = 0.032), respectively. Whereas, in the 5' UTR, allele C of rs1042711, G of rs11168070, C of rs11959427, and C of rs1801704 increased CPI by a fold of 10.86 (p = 0.00049), 5.99 (p = 0.016), 5.69 (p = 0.023), and 5.26 (p = 0.031), respectively. Together, these SNPs accounted for 2-15% of CPI variance after adjusting for covariates. Moreover, these SNPs were in high linkage disequilibrium (LD) showing three LD blocks in our cohort. A 10-marker haplotype increased CPI by 11.5-fold (p = 0.000407). Thus, ADRB2 polymorphisms might contribute to chronic pain severity and heterogeneity in SCD.