Understanding multi-level barriers to medication adherence among adults living with sickle cell disease

Abstract

There is limited research that identifies and examines multi-level barriers to medication adherence among adults with Sickle Cell Disease (SCD); Identify multi-level barriers to medication adherence among adults with SCD; and Examine the relationship between multi-level barriers and medication adherence levels. A cross-sectional study included 130 adults (ages ≥ 18 years old) living with SCD who receive treatment/care from one of the 10 adult SCD clinics within the Networking California for sickle cell care initiative. Study measures included the medication adherence report scale (Professor Rob Horne), Beliefs about Medicine Questionnaire (Professor Rob Horne), and patient reported outcomes measurement information system. Participants reported barriers to medication adherence across 3 levels: Community-level barriers (e.g., COVID-19 pandemic); Institutional-level barriers (e.g., bad experiences with the health care system); and Individual-level barriers (e.g., beliefs and depression severity). Depression severity and patient concerns about SCD medication were inversely correlated with medication adherence (r_s = −0.302, P < .001; r_s = −0.341, P < .001 respectively). Patient beliefs about the necessity of SCD medication were insignificantly correlated with medication adherence (r_s = 0.065, P = .464). Medication adherence was higher among patients who had fewer adherence barriers than multiple adherence barriers (Median medication adherence: fewer barriers = 22 vs multiple barrier = 20.50, P = .085), suggesting clinical significance although statistically insignificant. Identifying multi-level adherence barriers and examining their relationship with medication adherence will help develop targeted public health strategies to promote improved medication adherence and wellness among adults with SCD.

1. Introduction

Sickle cell disease (SCD) is the most common inherited blood disorder in the United States and affects approximately 100,000 Americans and 3.1 million people globally.^[1,2] In the United States, SCD predominately impacts individuals of African descent, followed by individuals of Hispanic, Middle Eastern, and Indian descent.^[3] In 1960, Sickle Cell Disease was considered a disease of childhood. However, 2 decades later, the Cooperative Study of Sickle Cell Disease reported that 95% of hemoglobin SS patients (in the United States) lived to adulthood.^[4] Use of penicillin prophylaxis, among other early intervention modalities, has increased the life expectancy of individuals living with SCD, particularly among those under the age of 5.^[5] Today, approximately 60% of individuals living with SCD are adults and the median age at death of an individual living with SCD is 43 years.^[1,6] Factors contributing to early mortality include limited access to comprehensive care, poor quality of care resulting in disjointed care delivery, and poor medication adherence.^[7]

In the realm of patient self-management, adherence and compliance are often used interchangeably. However, the World Health Organization strongly emphasized the importance of distinguishing between the 2 terms. It defines adherence as “the extent to which a person’s behavior- taking medication, following a diet, and/or executing lifestyle changes, corresponds with agreed recommendations from a health care provider”.^[8] Conversely, compliance is defined as “the extent to which a person’s behavior- in terms of taking medications, following diets, or executing lifestyle changes- coincides with medical or health advice”.^[9] Adherence presumes agreement with the recommendations given by a health care provider, while compliance presumes that a patient adopts a passive role in their treatment decision-making process. Furthermore, adherence involves the patient’s active participation in the treatment decision-making process.^[10]

Nonadherence generally assures that optimal health outcomes will not be achieved and there is some evidence that the very process of being adherent (even to a placebo) may itself incur some health benefits.^[11] Nonadherence can be classified into 2 primary categories: intentional and unintentional. Intentional nonadherence involves a deliberate choice by an individual to deviate from the prescribed treatment regimen, which may include skipping dosages.^[12] In contrast, unintentional nonadherence is characterized by a passive process in which an individual may forget or fail to adhere to the medication regimen due to a lack of understanding of the provided instructions.^[12] Effectively addressing poor adherence is important because poor adherence leads to increased morbidity, mortality, and health care costs (approximately 100 billion dollars per year).^[8,10] To buttress the importance of medication adherence, the World Health Organization stated that, “increasing the effectiveness of adherence interventions may have a far greater impact on the health of the population than any improvement in specific medical treatment”.^[8]

Hydroxyurea, a medication approved by the US food and drug administration for patients with SCD, has growing evidence to support its efficacy and cost-effectiveness in SCD.^[13] Although hydroxyurea is an effective disease-modifying therapy that can reduce acute complications of the disease and prevent deaths, its efficacy is tightly linked to good adherence.^[14] Nevertheless, hydroxyurea adherence remains a challenge with adherence rates being suboptimal, on average 50% to 60%.^[15,16] Hydroxyurea’s delayed onset of effectiveness and associated side effects are concerning for some patients, leading to poorer adherence.^[17] Different barriers to hydroxyurea adherence have been reported in the literature, including lack of understanding of hydroxyurea benefits and side effects; fear of side effects; doubts about efficacy; lack of access or insurance coverage; forgetfulness; and the need for more frequent laboratory monitoring and clinic visits.^[16,18] Some studies have identified recall barriers and negative beliefs as common obstacles to hydroxyurea adherence.^[16,19] Additionally, research suggests that patients with higher adherence rates tend to enjoy a better health-related quality of life than those with lower adherence levels.^[17,20] Conversely, increased barriers to hydroxyurea adherence are associated with poorer adherence and a decline in health-related quality of life.^[21] While hydroxyurea offers promising benefits in managing Sickle Cell Disease, addressing these barriers and improving adherence is crucial to maximizing its therapeutic potential and enhancing the quality of life for individuals with SCD.

There is limited research that identifies and examines multi-level barriers regarding medication adherence among adults living with SCD. This study adds to the literature by adopting a diverse participant pool and expanding on the current understanding of this population by identifying and understanding these barriers across multiple levels- individual, community, and institutional. The objectives of this study are; To identify multi-level barriers to medication adherence among adults living with SCD and; To examine the relationship between multi-level barriers and medication adherence levels.

2. Methods

2.1. Study design

This is a multi-institutional cross-sectional study. Utilizing a quantitative primary data analysis approach, data was collected from the Sickle Cell Disease Medication and Health Needs Assessment Survey. The research protocol was reviewed by the Loma Linda University Health Institutional Review Board and determined to be exempt from IRB approval as outlined in federal regulations for protection of human subjects, 45 CFR Part 46.101 (b)(2) (IRB# 5210509). Informed consent was obtained prior to study enrollment.

2.2. Participants and recruitment

A total of 137 out of 428 (32%) eligible adults living with SCD were successfully recruited from 10 adult sickle cell disease clinics within the Networking California for sickle cell care initiative (NCSCC), an effort led by the sickle cell disease foundation (SCDF) and the center for inherited blood disorders. Out of 137 participants, 130 (94.9%) had complete data and were included in the study. This network of clinics represents academic and medical centers in Northern, Southern, and Central California. Participants were eligible to participate in the survey if they; Had an SCD diagnosis (self-reported) and; Were 18 years or older. Community health workers (CHWs) from the SCDF were trained to recruit and administer the survey and given a telephone survey recruitment guide designed by the research team.

A convenience sample of patients within the NCSCC were enrolled in the study from March 2022 to April 2022 (5-week enrollment period) via telephone surveys. Of note, CHWs input participant’s responses during the telephone survey enrollment process. CHWs deployed various follow-up methods to recruit and enroll participants (e.g., phone calls, text messages, and email). After completion of the survey, respondents received a $10 gift card from the SCDF. The 10 clinics within the NCSCC are the following: Martin Luther King Outpatient Sickle Cell Center – Los Angeles; Center for inherited blood disorders – Orange; UC San Diego Medical Center – San Diego; UC Davis Medical Center – Sacramento; SAC Health System – San Bernardino; Loma Linda University Medical Center – Loma Linda; Kern Medical Center – Bakersfield; Community Cancer Institute – Fresno; Kaiser Permanente Inglewood- Inglewood, and; University of California, San Francisco Benioff- San Francisco.

2.3. Sickle cell disease medication and health needs assessment survey

The survey consisted of 25 questions designed to investigate barriers to SCD medication use, patients beliefs about the benefits and concerns associated with SCD medication, depressive symptoms, and medication adherence. The survey was anonymous and designed using an online survey platform called Qualtrics.^[22] The survey took approximately 10 to 15 minutes to complete and utilized validated instruments to assess all variables.

Study measures were adopted from the Adult Sickle Cell Quality of Life Measurement Information System, behavioral risk factor surveillance system, and patient reported outcomes measurement information system (PROMIS) to evaluate depressive symptoms and to identify associated demographic and clinical characteristics.^[23–25] Also, the medication adherence report scale (MARS-5) – (Professor Rob Horne) and the beliefs about medicine questionnaire (BMQ) – (Professor Rob Horne) were utilized to evaluate medication adherence levels and patient beliefs about medication. Permission was obtained from Professor Robert Horne to utilize the MAR-5 and BMQ scales.^[26,27]

2.4. Measurement of patient beliefs

Patients beliefs about their medicines were measured based on responses to the (BMQ - Professor Rob Horne), which is a validated scale that has been used with individuals living with SCD.^[28] The BMQ consists of 2 5-item scales assessing patients beliefs about the necessity of prescribed medication for controlling their illness and their concerns about the potential adverse consequences of taking it. Examples of items from the necessity scale include: “My medicines protect me from becoming worse” and “without my medicines I would be very ill”. Examples of items from the concerns scale include: “I sometimes worry about becoming too dependent on my medicines” and “I sometimes worry about long-term effects of my medicines”.

Participants indicated their level of agreement with each statement about medicines on a 5-point Likert scale, ranging from 1 = strongly disagree to 5 = strongly agree. Scores obtained from each item were summed to generate a scale score. The total score for the necessity and concerns scale ranged from 5 to 25. Higher scores indicated stronger beliefs in the concepts -necessity or concern.

The study assessed the balance between perceived benefits (necessity beliefs) and costs (concerns) associated with prescribed SCD medication. Given that the necessity and concerns scales assess negative and positive attitudes toward medication, a necessity-concerns differential was calculated. The necessity-concern differential provided an indication of the relative importance of these attitudes for individual patients where their perceptions of cost (concerns) are weighed against their perception of benefits (necessity beliefs). Adopted from Drs Horne and Weinman study conducted in 1999, a necessity-concerns differential was calculated as the difference between necessity and concern scores, resulting in a possible range of −20 to 20.^[29] If the difference was negative, the patient perceived greater costs than benefits. On the other hand, if the difference was positive, the patient perceived that the benefits of their medication outweigh the costs.

2.5. Measurement of depression severity

Depression severity was measured using the complete 4-item, PROMIS short-form for Emotional Distress-Depression, a validated scale that has been used with individuals living with SCD.^{[13,15,18,28,30–32]} This scale measures the frequency by which a participant experiences symptoms of depression over the past 7 days. Respondents indicated their level of agreement with each statement about their symptoms on a 5-point Likert scale, ranging from never to always. Examples of items from this scale include: “In the past 7 days, I felt hopeless” and “In the past 7 days, I felt depressed.” Item responses were uploaded to the Health Measures Scoring Service, where T-scores and related statistics were generated using PROMIS Wave 1 as the reference population, which is representative of the general adult population.^[33] Higher T-scores on these PROMIS measures indicate worse outcomes.

2.6. Measurement of adherence barriers

The number of adherence barriers was measured using 1 modified item from the sickle cell disease implementation consortium Registry Patient Enrollment Form. This study revised 1 item found in the “medical care barriers” section to address medication barriers while preserving the integrity of the question stem and answer choices. For example: “did you not get the medical care you needed or have delays getting medical care you needed for any of the following reasons?” was modified by replacing “medical care” or “care” with “medication” and adding “In the past 12 months” to the first part of the question. The new question stem was: “In the past 12 months, did you not get the medication you need or have delays getting medication you need for any of the following reasons?” Respondents selected all the reasons that apply to them or opted for the last option that states “this does not apply to me. I have not experienced any barriers or delays in getting the medication I need”. Respondents that selected the last option were coded as having 0 barriers. Examples of items in this scale include: “The Coronavirus/COVID-19 pandemic” and “you were too busy with work or other commitments”. Using the revised question, respondents that select 0 or 1 barrier were categorized as having “limited adherence barriers” and respondents that select 2 or more barriers were categorized as having “multiple adherence barriers.”

2.7. Measurement of medication adherence

Medication adherence was measured based on responses to the (MARS-5 - Professor Rob Horne), a widely used and validated self-administered questionnaire that has been used in a variety of people living with chronic illnesses.^[34] The MARS-5 is a 5-item scale that aims to collect information regarding patients level of adherence to their prescribed medication. It is a generic tool, which can be administered regardless of the disease and the prescribed drug.^[35] Furthermore, items in this scale are phrased in a nonjudgmental and nonthreatening way to minimize social desirability bias and normalize nonadherence.^[29] Examples of items in this scale include: “I stop taking them for a while” and “I take less than instructed”. Participants indicated their level of agreement with each statement about their nonadherence behavior on a 5-point Likert scale, ranging from never to always. Using MARS-5 Professor Rob Horne, the scores were defined on a continuous scale where higher scores indicate higher adherence, and lower scores indicate lower adherence.

2.8. Statistical methods

Descriptive statistics were reported in percentages and frequencies for categorical data and means and standard deviations for continuous variables. nonparametric analysis methods were adopted in this study (i.e., Mann–Whitney U test and Spearman correlation - r_s). IBM SPSS Statistics (Version 28) was used to conduct the statistical analysis. Prior to conducting the statistical analysis, 7 cases were dropped due to missing “annual household income” entries.

2.9. Study size

An a priori power analysis was conducted using G*Power version 3.1.9.7 to determine the minimum sample size to test the study hypothesis.^[36] Results indicated the required sample size to achieve 80% power for detecting a medium effect, at a significance criterion of α = .05, was N = 128 for a Mann–Whitney U test and N = 9 for a Spearman correlation test. Thus, the obtained sample size of N = 128 is adequate to test the study hypothesis.

3. Results

3.1. Participants

A cross-sectional survey was administered to 137 adults (ages ≥ 18 years old) living with SCD who receive treatment/care from one of the 10 adult SCD clinics within the NCSCC. Out of the 137 participants, 130 respondents were included in the study and analyzed. Per personal communication, 7 participants declined to answer the “annual household income” question.

3.2. Patient characteristics and reported outcomes

As seen in Table 1, the majority of the respondents were Black or African American (90%), female (67.7%), and between the age of 25 and 44 years (52.3%). Most adults living with SCD reported receiving the majority of their SCD care from a sickle cell specialist or hematologist over the past 2 years (82.3%) and visiting the emergency department between 1-2 times in the last 12 months (31.5%). The majority reported an annual household income of $25,000 and under (52.3%), completing some college or technical school (40.8%), and sometimes experiencing severe pain in the past 7 days (34.6%). It is worth noting that the majority of respondents perceived themselves as having good health (44.6%). As seen in Table 2, the average medication adherence score was 20.80 (SD = 3.66), patient concerns about SCD medication score averaged 14.14 (3.93), patient beliefs about the necessity of their SCD medication score averaged 16.98 (SD = 4.18), the average necessity-concern differential for respondents was 2.85 (SD = 5.55), and the average depression severity t-score was 50.79 (SD = 8.66).

Table 1.

Demographic Characteristics of the Respondents (N = 130).

Characteristics: n (%)
Age
18–24 yr old	36 (27.7)
25–44 yr old	68 (52.3)
45–64 yr old	26 (20.0)
Sex at birth
Male	42 (32.3)
Female	88 (67.7)
Race/ethnicity
Black or African American	117 (90.0)
Hispanic or Latino(a)	11 (8.5)
White or Caucasian	1 (0.8)
Asian	1 (0.8)
Annual household income
$25,000 and under	68 (52.3)
$25,001–$50,000	29 (22.3)
$50,001–$75,000	14 (10.8)
$75,001–$100,000	7 (5.4)
> $100,000	12 (9.2)
Highest level of education
Less than high school	1 (0.8)
Some high school	7 (5.4)
High school graduate or GED equivalent	33 (25.4)
Some college or technical school	53 (40.8)
College graduate or more	36 (27.7)
Emergency department visits
In past 12 mo
None	32 (24.6)
1–2	41 (31.5)
3–5	34 (26.2)
6–10	11 (8.5)
More than 10	12 (9.2)
Perceived health status
Excellent	8 (6.2)
Very good	21 (16.2)
Good	58 (44.6)
Fair	31 (23.8)
Poor	12 (9.2)
Have very severe pain
In past 7 d
Never	21 (16.2)
Rarely	22 (16.9)
Sometimes	45 (34.6)
Often	21 (16.2)
Always	21 (16.2)
Most Sickle cell disease care provided by
Over the past 2 yr
Sickle cell specialist or hematologist (including all care providers in the SCD clinic)	107 (82.3)
Primary care or general practice	15 (11.5)
Emergency department	6 (4.6)
I do not receive care for my sickle cell disease	2 (1.5)

SCD = sickle cell disease.

Table 2.

Patient reported outcomes (N = 130).

Outcome	Mean (SD)
Medication adherence*	20.80 (3.66)
Patient’s concerns†	14.14 (3.93)
Necessity beliefs‡	16.98 (4.18)
Depression severity§	50.79 (8.66)
Necessity-concerns differential∥	2.85 (5.55)

^*Composite score for the medication adherence report scale (MARS-5 - Professor Rob Horne) (scale score range: 5–25).

^†Composite score for the concern scale of the beliefs about medicines questionnaire (BMQ - Professor Rob Horne) (scale score range: 5–25).

^‡Composite score for the necessity scale of the beliefs about medicines questionnaire (BMQ - Professor Rob Horne) (scale score range: 5–25).

^§T-score generated from the patient reported outcomes measurement information system (PROMIS) health measures scoring service for the 4-item, PROMIS short-form for emotional distress-depression.

^∥Calculated as the difference between necessity and concern scores of the beliefs about medicines questionnaire (BMQ - Professor Rob Horne (range: −20 to 20).

3.3. Multi-level adherence barriers

Overall, the majority of the respondents reported experiencing 1 barrier (35.4%) followed by experiencing no barriers (32.3%), 2 barriers (14.6%), 3 barriers (9.2%), 4 barriers (6.2%), 5 barriers (1.5%), and 6 barriers (0.8%). Among the 88 respondents who reported experiencing 1 or more adherence barrier, the top 4 common barriers reported were: The Coronavirus/COVID-19 pandemic (30.7 %), having a previous bad experience with the health care system (29.5%), competing activity such as being too busy with work or other commitments (23.9%) and avoiding unwanted side effects associated with SCD medication (21.6%). All in all, participants reported barriers to medication adherence across 3 levels: Community-level barriers (e.g., the COVID-19 pandemic); Institutional-level barriers (e.g., bad experiences with the health care system); and Individual-level barriers (e.g., beliefs, behavior, and competing activity).

3.4. Nonadherent behavior

Nonadherent behavior (e.g., intentional and unintentional) can serve as a barrier to medication adherence. Using MARS-5 Professor Rob Horne, it was found that unintentional nonadherence was evident with 47.7% of the respondents reporting that they forgot to take their SCD medication. Intentional nonadherence was also common, approximately 1 to 3rd (33.8%) of the respondents reported not taking their SCD for a while, while some decided to miss (28.5%) or alter their dose (19.2%) or take less than instructed (20%).

3.5. Adherence barriers and medication adherence

Medication adherence was greater for patients who had fewer adherence barriers than multiple adherence barriers (Median medication adherence: fewer barriers = 22 vs multiple barrier = 20.50, P = .085), suggesting clinical significance although statistically insignificant (see Table 3).

Table 3.

Bivariate comparison^* of medication adherence levels for adults living with SCD who experience varying adherence barriers (N = 130).

Median	Limited adherence barriers† (N = 88)	Multiple adherence barriers‡ (N = 42)	P value
Medication adherence levels	22	20.50	.085

SCD = sickle cell disease.

^*A Mann–Whitney U test was performed to determine significant associations among variables.

^†Limited adherence barriers: the patient reported having 0 or 1 adherence barrier.

^‡Multiple adherence barriers: the patient reported having 2 or more adherence barriers.

3.6. Depression severity, patient concerns, patient beliefs about the necessity of their SCD medication, and medication adherence

Depression severity and patient concerns about their SCD medication were inversely correlation with medication adherence (r_s = −0.302, P = .001; r_s = −0.341, P < .001 respectively), suggesting higher medication adherence in patients with lower depression severity and lower medication adherence in patients with increased concerns about SCD medication. In addition, patient beliefs about the necessity of their SCD medication was insignificantly correlated with medication adherence (r_s = 0.065, P = .464).

4. Discussion

The study adds to the literature by adopting a larger population size and diverse participant pool and expanding on the current understanding of people living with SCD by identifying and understanding barriers to adherence across multiple levels. The study identified multi-level barriers to medication adherence and examined the relationship between these multi-level barriers to medication adherence. Based on the findings, patients who reported lower depressive symptoms and decreased concerns (i.e., negative beliefs) about their SCD medication were more likely to have higher medication adherence levels, highlighting the need to address patients concerns about SCD medication to improve medication adherence levels. As presented by previous literature, this study remains consistent with other findings in which patients reporting poor adherence were associated with depression and negative beliefs.^[28,36] Of note, concerns about the side effects of their SCD medication served as one of the top barriers to medication adherence, which is consistent with previous studies.^[17,37]

As presented by previous literature, this study remains consistent with other findings in which patients with fewer barriers are more likely to have higher medication adherence levels.

Although our study was not able to establish a significant relationship between the number of adherence barriers and adherence, a previous study found that patients with no or fewer adherence barriers have higher adherence levels, suggesting the need for further investigation regarding overall SCD medication adherence. These findings suggest that, in adults living with SCD, efforts to lower adherence barriers could improve adherence levels. Furthermore, the study found that patients experienced individual, community, and institutional-level barriers to medication adherence. Individual-level barriers included patient beliefs, nonadherent behavior, and competing activity (e.g., being too busy with work or other commitments). The COVID-19 pandemic was a reported community-level barrier. Institutional-level barriers included a patient’s bad experience with the health care system.

Although identification of multi-level barriers provides critical information, there is still a need to further investigate the specifics of or reasons behind the identified multi-level adherence barriers to gain a deeper understanding of these adherence barriers. In addition, this study served as a pilot study in California, so future studies could expand beyond state borders to gain a richer understanding of multi-level adherence barriers among adults with SCD across the nation.

The findings of having moderate to high medication adherence are contrary to previous studies, highlighting the unique nature of the sample. The reported adherence levels could be attributed to several factors. For 1, the respondents were recruited from the SCDF’s client database, signifying their connection to a large social support network which includes CHWs who serve as a link between the patient and the healthcare system and other critical resources. Also, the average reported necessity-concern differential was 2.85 (SD = 5.55), suggesting that respondents perceived greater benefits than costs when thinking about their SCD medication. Lastly, experiencing limited adherence barriers (67.7%) and receiving a majority of their care from an SCD specialist or hematologist (82.3%) could also attribute to higher medication adherence.

From a policy perspective, recommendations from this study can help implement a targeted and strategic policy that encourages community-based organizations devoted to improving the health and wellbeing of adults living with SCD to focus on assessing the number of adherence barriers, levels of depression severity and patients concerns about SCD medication. community-based organizations can develop interventions specifically tailored to their client’s needs to help navigate issues or obstacles in the healthcare system. Implementing such policies can support adults with SCD experiencing high levels of depression, concerns about their SCD medication, and multi-level adherence barriers.

There are several possible limitations and strengths in this study. First, medication adherence, depression severity, and patient beliefs were evaluated using validated self-report measures. The use of self-report questionnaires can lead to methodological limitations such as recall bias, overreporting, and social desirability bias.^[29] The use of validated scales in a wide range of chronic illness groups lowers the threat to internal validity. Second, a strength of this study is that it is a multiple institution study involving an array of academic and medical clinics, which could lead to more generalizable results. Furthermore, our study is cross-sectional in design, so we would be limited in our ability to make strong statements about the true causal directionality of the observed relationships. The use of a relatively small sample size and the discussion of some statistically insignificant results pose limitations to this study. Lastly, medication adherence was examined broadly, thus, work is needed to examine medication adherence among SCD patients to specific treatment modalities (e.g., including Endari, Adakveo, Oxbryta, iron chelation, recommended self-care behaviors, and chronic blood transfusions).

5. Conclusion

The findings of the study provide critical information for medication adherence and health promotion efforts among adults living with SCD. In addition, it will help raise more awareness on the issue of multi-level barriers as it relates to medication adherence. Overall, understanding the multi-level adherence barriers among adults with SCD will help improve structural and systemic public health efforts toward promoting improved medication adherence and wellness through targeted strategies that address each barrier at its respective level-individual, community, and institutional.

Acknowledgments

Thank you to Dr Queen-Ivie C. Egiebor Doctoral Project Guidance Committee for substantive and timely feedback in improving the quality of the manuscript. Specific individuals include Dr Karl J. McCleary, Dr Jim E. Banta, Dr Ronald Mataya, and Dr Wendy Shih. Also, thank you to the Sickle Cell Disease Foundation (SCDF) for making this project possible. Specific individuals include Tina E. Coleman, MPH, Mary E. Brown, Patrice L. Ragin, Portia Langdon, Deborah Green, Yadira Durán Badwan, Anthony C. Wells, Keyasia Currie, Sharod L. Johnson, and Ashley Marlynn Meneses. Thanks to Dr Chanell Grismore, DrPH, MPH, MCHES, the Director of the Sickle Cell Center at Loma Linda University Health. Lastly, thank you to Professor Rob Horne from the UCL School of Pharmacy for giving us permission to use the Beliefs about Medicine Questionnaire (BMQ) and the Medication Adherence Report Scale (MARS-5). Partial funding for this project was provided by the Sickle Cell Disease Foundation.

Author contributions

Conceptualization: Ivie Cleopatra Egiebor, Karl J McCleary, Jim E Banta, Ronald Mataya, Wendy Shih.

Data curation: Ivie Cleopatra Egiebor.

Formal analysis: Ivie Cleopatra Egiebor.

Investigation: Ivie Cleopatra Egiebor, Karl J McCleary.

Methodology: Ivie Cleopatra Egiebor, Karl J McCleary, Jim E Banta, Ronald Mataya, Wendy Shih.

Project administration: Ivie Cleopatra Egiebor, Karl J McCleary

Resources: Ivie Cleopatra Egiebor.

Supervision: Karl J McCleary, Jim E Banta, Ronald Mataya, Wendy Shih.

Writing – original draft: Ivie Cleopatra Egiebor.

Writing – review & editing: Ivie Cleopatra Egiebor, Karl J McCleary, Jim E Banta, Ronald Mataya, Wendy Shih.