Abstract
Sickle cell disease (SCD) is a collection of inherited blood disorders that affect a substantial number of people in the U.S., particularly African Americans. People with SCD have an abnormal type of hemoglobin, Hb S, which polymerizes when deoxygenated, causing the red blood cells to become misshapen and rigid. Individuals with SCD are at higher risk of morbidity and mortality from infections, vaso-occlusive pain crises, acute chest syndrome, and other complications. Addressing the public health needs related to SCD is an important step toward improving outcomes and maintaining health for those affected by the disorder. The objective of this study was to review public health activities focusing on SCD and define the need to address it more comprehensively from a public health perspective. We found that there has been some progress in the development of SCD-related public health activities. Such activities include establishing newborn screening (NBS) for SCD with all states currently having universal NBS programs. However, additional areas needing focus include strengthening surveillance and monitoring of disease occurrence and health outcomes, enhancing adherence to health maintenance guidelines, increasing knowledge and awareness among those affected, and improving healthcare access and utilization. These and other activities discussed in this paper can help strengthen public health efforts to address SCD.
Introduction
Sickle cell disease (SCD) comprises a group of inherited blood disorders that are life-long and affect many people globally. The WHO estimates that SCD affects 275,000 conceptions each year.
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In the U.S., SCD is seen more commonly among people of African descent and people (or their descendants) from parts of tropical and subtropical regions where malaria is or was common, such as individuals with an Hispanic, Mediterranean, or Southeast Asian background. However, because the U.S. population is not ethnically homogenous, it is important that SCD not be seen as occurring exclusively among these groups.The purpose of this paper is to assess existing public health programs and define the need to achieve a more comprehensive public health approach for reducing morbidity and mortality related to SCD in the U.S. Using the essential public health services as a framework, we examined existing public health–related activities addressing SCD; we also identified opportunities—while assessing gaps—toward a greater and broader public health focus on health promotion and disease prevention.
Disease Characteristics
Sickle cell disease is characterized by the presence of sickle hemoglobin (Hb S) in red blood cells.
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It is an autosomal recessive genetic disorder. Individuals who are heterozygous are carriers and are referred to as having sickle cell trait (SCT). Individuals who are homozygous or compound heterozygous for the mutation have SCD. Most SCD in the U.S. comprises one of four genotypes: sickle cell anemia (Hb SS); sickle-hemoglobin C disease (Hb SC); and two types of sickle β-thalassemia (Sβ+-thalassemia and Sβ0-thalassemia). Among disorders identified by newborn screening (NBS), SCD is the most common, with approximately 1800 births recorded by states that reported cases in 2006 (genes-r-us.uthscsa.edu).Among people with SCD, sickled red blood cells may occlude small blood vessels and capillaries, resulting in a lack of oxygen for the tissues. This causes the episodes of pain—which can be severe—that many people with SCD suffer. It also can result in acute and chronic organ damage. Children with SCD are at risk of life-threatening infections.
5
People with SCD also are at higher risk of stroke, acute chest syndrome, leg ulcers, pulmonary hypertension, and other complications.5
Although SCT generally is a benign and asymptomatic state, red blood cell sickling and splenic infarction can occur at low oxygen levels such as at high altitudes. Research suggests that SCT is associated with a number of other complications that are usually relatively infrequent or occur under conditions of severe biological stress.6
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Public Health and Reducing Disease and Disability
The goals of public health are to prevent disease and injury and promote health. Strategies to improve health and prevent disease have a major focus on the healthy state of individuals, and this applies also to improving and maintaining health among people with SCD. In addition, strategies also need to be undertaken to prevent mortality, disability, and other morbidity. This has particular considerations related to individuals with chronic genetic disorders such as SCD as many such people are at a greater risk for morbidity and mortality.
Health promotion, early detection and intervention, and other activities discussed in this paper are integral to the purposes of public health and are consistent with the Ten Essential Public Health Services
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defined by the collaborative effort of national organizations and federal agencies; these are:- 1monitor health status to identify and solve community health problems;
- 2diagnose and investigate health problems and health hazards in the community;
- 3inform, educate, and empower people about health issues;
- 4mobilize community partnerships to identify and solve health problems;
- 5develop policies and plans that support individual and community health efforts;
- 6enforce laws and regulations that protect health and ensure safety;
- 7link people to needed personal health services and assure the provision of health care when otherwise unavailable;
- 8assure a competent public and personal healthcare workforce;
- 9evaluate effectiveness, accessibility, and quality of personal and population-based health services; and
- 10research for new insights and innovative solutions to health problems.
Sickle Cell Disease Newborn Screening
Newborn screening for SCD consists of identifying a neonate's sickle cell hemoglobin status at the time of or soon after birth. An early NBS program for SCD was implemented in New York State in 1975.
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In the late 1970s and early 1980s, statewide programs were implemented in Colorado, Texas, and Georgia. These programs showed the effectiveness of these approaches and provided valuable knowledge on different strategies for NBS.12
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As of January 2006, all states and Puerto Rico and the Virgin Islands had implemented universal screening for SCD. State NBS programs use filter paper for their screening tests, placing blood on the filter paper.15
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Confirmatory testing of infants with positive neonatal screening results and diagnosis require hemoglobin separation by electrophoresis (cellulose acetate and citrate agar), isoelectric focusing, or high-performance liquid chromatography. Depending on state policies, NBS programs vary as to whom they report positive screening results and whether all, some, or no carriers of hemoglobinopathies are actively followed up.17
There also is variation in the methods used for communicating results to those followed up with and in screening and information disclosure–related consent procedures.17
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A number of recent studies provide information indicating effectiveness of NBS programs in the U.S. and elsewhere
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(Table 1). A recent study by Frempong and Pearson19
found that there were fewer SCD-related deaths among children after implementation of universal NBS in Connecticut in 1990. In the NBS program studied, if the screening result indicated a major hemoglobinopathy, the delivery provider, pediatrician (if known), parents, and one of the sickle cell centers were informed. For successful health outcomes, the study suggested the need for comprehensive follow-up care of infants as well as further screening tests. Another recent study that evaluated a NBS program in Jamaica also reported that hospital admissions and occurrence of serious illness were reduced among patients with SCD because of NBS and early interventions.20
Table 1Selected recent studies assessing impact of NBS programs for SCD
Study | Characteristics of the screening program | Findings related to impact of the program |
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EPI, Expanded Program on Immunizations; Hb CC, homozygous hemoglobin C disease; Hb SC, sickle-hemoglobin C disease; Hb SS, sickle cell anemia; NBS, newborn screening; PCP, primary care provider; PCV7, heptovalent pneumococcal-conjugated vaccine; SCD, sickle cell disease; SCU, sickle cell unit
a As described in this paper.
Newborn screening program activities are mechanisms by which public health has helped to reduce morbidity and mortality and improve the well-being of people with SCD. The activities of state NBS programs in the U.S., for example, apply principles related to detection of health problems, implementing policies and practices to address these, promoting partnerships and coordination among various entities, informing and educating the public, and linking people to health services. These activities are consistent with the essential services of public health. However, more needs to be done. Currently, there are no standardized NBS follow-up guidelines for SCD. Such guidelines could include information related to whom to follow-up with positive results, what information to convey, provider follow-up protocols, and what modes of communication are best. NBS programs have also been less successful in providing an ongoing and systematic approach of long-term follow-up, along with health promotion and disease prevention interventions for individuals with SCD beyond the newborn period and for activities related to SCT.
Surveillance and Monitoring
Epidemiologic information—such as incidence and prevalence of disease, risk factors, and health impact—helps in developing and strengthening strategies for reducing morbidity and mortality from SCD. Recent studies assessing SCD prevalence in the U.S. estimate that approximately 90,000 people have SCD.
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Among neonates with SCD in California, the prevalence of SCD was reported to be one per 396 births among African Americans; 6% of neonates with SCD were reported to be among Hispanic Americans.25
A study assessing NBS among infants born in California, Massachusetts, North Carolina, and Wisconsin reported rates of occurrence of 17.7, 17.4, and 2.0 per 10,000 births for Hb SS, Hb SC, and Hb S/β-thalassemia, respectively, during the time period 2001–2006.26
Although a number of individual studies have focused on the epidemiology SCD, population-based disease surveillance activities and disease registries are also needed. Surveillance information is needed for the development and implementation of programs and strategies for reducing morbidity and mortality, such as through appropriate follow-up, referral, and delivery of services. Public health activities need to be implemented at state and local levels for continued collection, assessment, and use of information related to SCD occurrence. Coordination and support at the national level should help facilitate this. Clinical registries obtain longitudinal information and are effective mechanisms for researching and identifying the effectiveness of treatments and assessing improvements in outcomes. Public health efforts should focus on the development of model procedures, tools, evaluation steps, and related research. Implementing and strengthening surveillance-related genetic and biomolecular laboratory support at national, state, and local levels, as applicable, are also imperative.
Recent efforts to improve surveillance and monitoring related to SCD include the Registries and Surveillance for Hemoglobinopathies (RuSH) project coordinated by government agencies including the CDC, Health Resources and Services Administration, the NIH, and seven pilot states (www.cdc.gov/sicklecell). The immediate goals of the RuSH project are to find out the number of people that have SCD or clinically significant thalassemia, develop plans for a national surveillance system to acquire better knowledge about the disorders, and improve knowledge and awareness among the general public about the disorders. The RuSH project will help to develop better knowledge about how people's health is affected by SCD and thalassemia.
Prevention of Complications and Improvement of Health Outcomes
Sickle cell disease has a deleterious effect on immune system functions, and thus children with SCD are at increased risk of life-threatening infections, especially with Streptococcus pneumoniae and Haemophilus influenzae.
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However, many of the infections are preventable. The strong protective effect of penicillin prophylaxis has been demonstrated by several studies.30
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According to a clinical guideline for the management of SCD, children with Hb SS or sickle Sβ0-thalassemia should receive regular penicillin prophylaxis from as early as age 2 months through 5 years, and parents should have the option to continue prophylaxis for patients aged more than 5 years; for patients with Hb SC, penicillin prophylaxis has been stated to be probably wise.16
In addition to antibiotic prophylaxis, children with SCD need to be up to date with routinely recommended vaccines, including pneumococcal and H. influenzae type b (Hib) vaccines. Children with SCD should receive both the 13-valent pneumococcal-conjugated vaccine (PCV13) starting at age 2–6 months and the 23-valent polysaccharide vaccine from age 2 years.
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In a study conducted among children with SCD in metropolitan Atlanta, having one or more doses of heptovalent PCV (PCV7) was 81.4% effective in preventing pneumococcal infection after controlling for herd immunity.35
Yanni and colleagues36
found significant declines in mortality rates among children aged 0–3 years from the period 1994–1998 to the period 1999–2002 after not decreasing during the 1990s, and proposed that the decline in the mortality rate was related to the implementation of PCV7 vaccination beginning in 2000.Available information suggests that nonadherence to regular prophylaxis may be occurring among a substantial proportion of children with sickle cell anemia.
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Limited information is available on immunization rates among children with SCD. The failure to have all children with SCD receive appropriate prophylaxis may result in pneumococcal as well other organism infections among these children that could be prevented. These not only cause pain and suffering, but also result in healthcare and related expenditures. Public health efforts, when appropriate, are needed for the promotion of adherence among children prescribed regular penicillin prophylaxis and the receipt of all recommended pneumococcal and other vaccines.- Adamkiewicz T.V.
- Sarnaik S.
- Buchanan G.R.
- et al.
Invasive pneumococcal infections in children with sickle cell disease in the era of penicillin prophylaxis, antibiotic resistance, and 23-valent pneumococcal polysaccharide vaccination.
J Pediatr. 2003; 143 (Erratum in: J Pediatr 2004;144(3):412): 438-444
Investigators have used counseling during clinic visits as a mechanism for improving compliance with penicillin prophylaxis among patients with SCD.
37
Elliot and colleagues40
found that the number of hospitalizations and demographic and socioeconomic factors (such as the number of adults and children in the household and having a car) were related to compliance ratings associated with penicillin prescribed in liquid form. Evidence-based strategies, such as reminders and provider and/or patient education, have been developed for improvement of various health-related practices.41
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These principles can be helpful toward guiding activities related to SCD. Development, translation, and broader implementation of strategies for prophylaxis adherence and immunization, as appropriate, should help to improve health outcomes for people with SCD. These types of strategies also may be applicable for other interventions.43
For example, patients with SCD who receive chronic blood transfusions may be at greater risk of developing iron overload. Ensuring compliance among patients prescribed iron chelation therapy is therefore very important.44
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Causes of death among patients with SCD include cardiopulmonary causes such as cardiac arrest, heart failure, and pulmonary embolism, infections, stroke, and multiorgan failure.
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Among children hospitalized with SCD, frequent complications include infections and pulmonary conditions.47
A longitudinal study of patients with SCD in several clinical centers reported sickle cell pain crisis and acute chest syndrome as the most frequent clinical events during the first 10 years of life.27
Pain crisis is a common cause of emergency department visits among both children and adults with SCD and is also a frequent cause of hospitalization.49
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Improvements are needed in pain management among patients with SCD, identification of best practices for such care, and the development of management guidelines, for example, in emergency departments.52
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As asthma may affect outcomes in SCD, research should be implemented to better understand the association and appropriate management in such cases.55
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Blood transfusions are a therapeutic measure among many people with SCD. Among hospitalized patients with SCD, transfusions are a frequent procedure.47
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In this regard, it is important to maintain and improve as necessary blood product transfusion safety.57
Improvements are also needed in other aspects of medical care for patients with SCD, including preventing organ damage and other complications and maintaining health.Over the past years, considerable progress has been achieved in reducing morbidity and mortality related to SCD among children.
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For example, a study by Fullerton et al.58
indicated that the incidence of stroke among children with SCD in California declined after 1998. According to the authors, it was possible that the decline may have been related to preventive transfusions among children with high-risk SCD. However, as discussed in the previous text, more improvements are urgently needed to improve health outcomes among people with SCD. Comprehensive efforts to address this should include improving knowledge and understanding through research, identification of effective interventions and strategies, and promoting translation and implementation.Increasing Knowledge and Awareness and Health Promotion
For people with SCD and the parents of children with SCD, knowledge related to complication prevention and health maintenance is imperative. These include preventing dehydration; avoiding exposure to severe cold or heat; preventing infections; maintaining appropriate nutrition, recognizing and getting early medical follow-up for symptoms such as fever; and implementing pain evaluation and management.
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Additionally, it is important to provide SCD-related genetic counseling and information about the health risks and options to those who are affected.60
A survey of state and territorial NBS programs in 1998 reported substantial variation among the programs in providing counseling (e.g., variation in the diseases and the type of test result related to which counseling is provided).61
Information and awareness-related activities, therefore, should be an important component of effective public health strategies for reducing morbidity and mortality among people with SCD. Follow-up of infants with positive NBS results and provider contacts are among opportunities of where to try to enhance complication prevention knowledge and practice. Possible methods for delivery of such information include direct counseling, provision of information material, and referral to other sources. In a study evaluating written informational materials provided to children with SCD and their family members; nearly all respondent caregivers (96%) indicated that they found the materials to be helpful.
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Awareness activities through community-based organizations, support groups, and advocacy organizations also may provide effective avenues to reach people with SCD.Facilitating Better Healthcare Utilization
People with SCD need to receive comprehensive medical care that includes specialized care by a hematologist.
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Children should have routine health visits approximately every 2–3 months during their first 2 years of life, and after that, visits should be as needed, but at least semiannually.16
Specialized treatment centers, such as comprehensive SCD treatment centers, can provide disease-specific comprehensive care encompassing various medical expertise and services.63
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However, the number of specialized centers is limited, and sufficient access to them does not exist nationwide. Health services delivered through a primary care provider–coordinated medical home or a chronic care model may be better geared to provide primary and preventive care services.63
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Day hospitals also have been reported to be a useful and effective health service delivery mechanism, particularly for treatment of sickle cell crisis or pain episodes.66
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These are ambulatory-type settings that are geared to manage uncomplicated vaso-occlusive crises.A substantial proportion of both children and adults with SCD rely on Medicaid for healthcare coverage.
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A study assessing hospitalizations in the U.S. among patients with SCD found that the primary payer type for 66% of hospitalizations with a principal diagnosis of SCD was Medicaid.47
Better understanding is needed on health insurance coverage among people with SCD.70
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, 72
In a study conducted between 1996 and 2000, Kass and colleagues70
interviewed parents of children and people with or at higher risk of selected genetic or chronic diseases or HIV and found that 27% of respondents reported having experienced difficulty obtaining health insurance, and one third thought they would face difficulty obtaining health insurance in the future.Improving utilization will require focus in terms of needs assessments, identification of gaps and barriers, development of applicable strategies, and evaluation. In this regard, more research is needed related to how to best provide health care to people with SCD. Research findings have suggested that the frequency of primary care provider visits, as well as visits to specialists, among people with SCD may be less than optimal.
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Studies also have indicated that people with SCD are much more likely to use emergency department services than the general population.73
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Information also is needed on access to and utilization of appropriate treatment. For example, are all patients who should receive hydroxyurea receiving the therapy? Reported barriers to therapy have included issues related to compliance and laboratory monitoring.76
In addition, there is need for increased availability of providers with knowledge and expertise on SCD. Considerations to achieve this include increased medical training options related to SCD management.Recently, the USDHHS was given a charge to make SCD a priority focus area (www.minorityhealth.hhs.gov/templates/browse.aspx?lvl=2&lvlid=206). The substantial need for more efforts to increase access and improve health care and outcomes for people with SCD was a principle guiding the endeavor. To address this need, DHHS has charted actions related to improving surveillance activities, access to health care and other services, development of new drugs, and research with a biomedical and behavioral focus.
Conclusion
It has been almost 4 decades since the passage of the National Sickle Cell Anemia Control Act of 1972. This Act aimed to address the early identification of individuals with SCD and their ongoing treatment in a comprehensive manner. This article focused on several issues related to health among people with SCD. There are also other important areas that need to be included in public health efforts, for example, pregnancy and childbirth, psychological effects such as depression, social effects such as lower educational achievement and difficulty finding employment, as well as important considerations and deliberations related to genetic counseling such as carrier status knowledge and prenatal diagnosis. Although we did not discuss these in this article because of space limitations, no less importance is implied, because these and other issues also should be considerations of public health activities addressing SCD.
There has been progress in public health activities addressing SCD. However, more efforts are needed. Issues needing more focus include that, to date, there are no standardized NBS-related follow-up procedures across the U.S. There are gaps in surveillance and monitoring efforts, research delineating disease epidemiology, and population-based programs that can help reduce morbidity and mortality among people with SCD. In addition, healthcare access and utilization is less than optimal. Most people with SCD are African Americans and other ethnic or racial minorities. As such, historical and cultural contexts are important to consider. Also important to consider is that programs and strategies focused on or coordinated with socioeconomic and environmental factors that affect health may often be more effective. For example, poverty, unemployment, lack of education, weak social support structures, and related disparities are factors that may affect health and well-being, and these considerations could help efforts to improve health.
Nationally, we need a public health agenda for SCD that has as its basis the essential services of public health. Addressing issues and concerns discussed in this paper, as well as others, can help strengthen the public health focus on SCD.
Publication of this article was supported by the Centers for Disease Control and Prevention through a Cooperative Agreement with the Association for Prevention Teaching and Research award # 09-NCBDDD-01.
The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the CDC Health Resources and Services Administration or the DHHS.
No financial disclosures were reported by the authors of this paper.
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