Sickle Cell Trait from a Metabolic, Renal, and Vascular Perspective: Linking History, Knowledge, and Health

The Bias of Medicine in Sickle Cell Disease

Sickle cell disease (SCD) is the most common monogenetic condition in the United States (US) and one that has been subjected to a history of negative bias. Since SCD was first described approximately 120 years ago, the medical establishment has, directly and indirectly, harmed patients by reinforcing biases and assumptions about the disease. Furthermore, negative biases and stigmas have been levied upon patients with SCD by healthcare providers and society, researchers, and legislators. This article will explore the historical context of SCD in the US; discuss specific issues in care that lead to biases, social and self-stigma, inequities in access to care, and research funding; and highlight interventions over recent years that address racial biases and stigma.

Parents' Experiences and Needs Regarding Infant Sickle Cell Trait Results

BACKGROUND AND OBJECTIVE

Sickle cell trait (SCT) has reproductive implications and can rarely cause health problems. SCT counseling improves parent knowledge but is infrequently received by children with SCT compared with children with cystic fibrosis carrier status. There are no national guidelines on SCT disclosure timing, frequency, or counseling content. Parents' experiences with SCT disclosure and counseling are poorly understood but could inform the development of guidelines. We explored parents' experiences with and desires for SCT disclosure and counseling for their infants with SCT identified via newborn screening.

METHODS

Parents of infants 2 to 12 months old with SCT were recruited through a state newborn screening program for semistructured interviews to explore their experiences with and desires for SCT disclosure and counseling. Inductive thematic analysis was conducted.

RESULTS

Sixteen interviews were completed from January to August 2020. Most parents reported that SCT disclosure occurred soon after birth, in person, and by the child's physician. Five themes were identified: parent knowledge before child's SCT disclosure, family planning, the dynamics of SCT disclosure and counseling, emotions and actions after SCT disclosure, and parent desires for the SCT disclosure and counseling process. Two primary parent desires were revealed. Parents want more information about SCT, particularly rare symptomatology, and they want SCT counseling repeated once the child approaches adolescence.

CONCLUSION

Parents report receiving their child's SCT diagnosis in the early newborn period from their child's doctor but indicate they receive incomplete information. Opportunities exist in primary care pediatrics to better align SCT disclosure timing and counseling content with parent desires.

Challenging the dogma of the healthy heterozygote: Implications for newborn screening policies and practices

Heterozygous (carrier) status for an autosomal recessive condition is traditionally considered to lack significance for an individual's health, but this assumption has been challenged by a growing body of evidence. Carriers of several autosomal recessive disorders and some X-linked diseases are potentially at risk for the pathology manifest in homozygotes. This minireview provides an overview of the literature regarding health risks to carriers of two common autosomal recessive conditions on the Recommended Uniform Screening Panel: sickle cell disease [sickle cell trait (SCT)] and cystic fibrosis (CF). We also consider and comment on bioethical and policy implications for newborn blood screening (NBS). Health risks for heterozygotes, while relatively low for individuals, are often influenced by intrinsic (e.g., other genomic variants or co-morbidities) and extrinsic (environmental) factors, which present opportunities for personalized genomic medicine and risk counseling. They create a special challenge, however, for developing screening/follow-up policies and for genetic counseling, particularly after identification and reporting of heterozygote status through NBS. Although more research is needed, this minireview of the SCT and CF literature to date leads us to propose that blanket terms such as "healthy heterozygotes" or "unaffected carriers" should be superseded in communications about NBS results, in favor of a more nuanced paradigm of setting expectations for health outcomes with "genotype-to-risk." In the molecular era of NBS, it remains clear that public health needs to become better prepared for the full range of applied genetics.

Splenic infarction in sickle cell trait: A comprehensive systematic review of case studies

Sickle cell trait (SCT), a commonly asymptomatic condition, has many associated clinical complications that upon presentation, can be very difficult to attribute to SCT. The effects of SCT on the spleen, for example, are not completely understood, though there have been a number of case reports detailing related complications in diverse populations. Our objective was to perform the first comprehensive case report review of splenic infarction in SCT patients to highlight the relevance of this seemingly rare condition. We conducted an extensive literature search reviewing case reports and case series of acute splenic infarctions from 1970 to 2020. This comprehensive search resulted in 54 articles with a total of 85 individuals. The ages ranged from 7 to 65, 12% were female. Individuals were of African‐American (26%), European (16%), South Asian (13%), Middle Eastern (7%), Latin American (7%), North or East African (4%), Mediterranean (4%), West African (1%), and unknown (22%) origins. Although splenic infarct in SCT patients has been associated with high altitudes, 39% of cases reporting altitude occurred below 3000 m. Among cases where HbS values were recorded, 88% occurred in individuals with HbS levels higher than 35%, suggesting that high HbS values may be a risk factor for splenic infarction. Our findings indicate that splenic infarct occurs across a wide range of demographic populations and environmental settings. While our understanding of SCT evolves, the findings here suggest that future advances in research and healthcare could benefit more from real‐time surveillance and registry initiation for various SCT outcomes such as splenic infarct.

Prospective Newborn Screening for Sickle Cell Disease and Other Inherited Blood Disorders in Central Malawi

Objectives: Newborn screening in the United States and Europe allows early identification of congenital disorders but does not yet exist in most low-resource settings, especially in sub-Saharan Africa. Newborn screening can identify multiple inherited hematological disorders, but feasibility and effectiveness for Africa are not fully determined. Methods: Surplus dried blood spot collected in Central Malawi through the HIV Early Infant Diagnosis surveillance program were repurposed and tested by isoelectric focusing for sickle cell disease and trait. Additional genetic testing identified G6PD deficiency and alpha thalassemia. Results: Testing of 10,529 cards revealed an overall sickle cell trait prevalence of 7.0% (range 3.9-9.7% by district); 10 of 14 infants identified with sickle cell disease (prevalence 0.1%) were located and received care at a specialized clinic. Subsequent testing of 1,329 randomly selected cards identified alpha thalassemia trait in 45.7% of samples, and G6PD deficiency in 20.4% of males and 3.4% of females, with 29.0% of females as heterozygous carriers. Conclusion: Inherited hematological disorders are common in Central Malawi; early identification through newborn screening can improve clinical outcomes and should be supported throughout Africa.

Gene therapy as the new frontier for Sickle Cell Disease

Sickle Cell Disease (SCD) is one of the most common monogenic disorders caused by a point mutation in the β-globin gene. This mutation results in polymerization of hemoglobin (Hb) under reduced oxygenation conditions, causing rigid sickle-shaped RBCs and hemolytic anemia. This clearly defined fundamental molecular mechanism makes SCD a prototypical target for precision therapy. Both the mutant β-globin protein and its downstream pathophysiology are pharmacological targets of intensive research. SCD also is a disease well-suited for biological interventions like gene therapy. Recent advances in hematopoietic stem cell (HSC) transplantation and gene therapy platforms, like Lentiviral vectors and gene editing strategies, expand the potentially curative options for patients with SCD. This review discusses the recent advances in precision therapy for SCD and the preclinical and clinical advances in autologous HSC gene therapy for SCD.

Pregnancy in sickle cell trait: what we do and don't know

Sickle cell trait (SCT) is the carrier state for sickle cell disease that results from the HBB rs334 missense mutation (p.Glu6Val) in the β-globin chain of haemoglobin. While not associated with any impact on life expectancy, it has been established that SCT is associated with an increased risk of both venous thromboembolism (and in particular, pulmonary embolism) and chronic kidney disease. It is largely unknown what short- or long-term effect, if any, pregnancy has upon the risk or outcomes of these disorders. In addition, SCT has been linked with various adverse outcomes in pregnancy, ranging from maternal complications such as elevated risk of bacteriuria to potentially life-threatening entities such as pre-eclampsia and prematurity. In these scenarios also, no clear association with SCT has been established. Given the high worldwide prevalence of SCT, further studies addressing these issues are warranted.

Sickle cell carriers' unmet information needs: Beyond knowing trait status

Benefits of identifying sickle cell disease (SCD) carriers include detection of at-risk couples who may be informed on reproductive choices. Studies consistently report insufficient knowledge about the genetic inheritance pattern of SCD among people with sickle cell trait (SCT). This study explored perspectives of adults with SCT on the information needed to make an informed reproductive decision and the recommendations for communicating SCT information. Five focus groups (N = 25) were conducted with African Americans with SCT ages 18-65 years old. Participants were asked about their knowledge of SCT, methods for finding information on SCT, impact of SCT on daily living, and interactions with healthcare providers. An inductive-deductive qualitative analysis was used to analyze the data for emerging themes. Four themes emerged, highlighting the unmet information needs of African American sickle cell carriers: (a) SCT and SCD Education; (b) information sources; (c) improved communication about SCT and SCD; and (d) increased screening strategies. Future studies are needed to determine effective strategies for communicating SCT information and to identify opportunities for education within community and medical settings. Identifying strategies to facilitate access to SCT resources and education could serve as a model for meeting unmet information needs for carriers of other genetic conditions.

'It means everyone should know their status': exploring lay conceptions of sickle cell trait and sickle cell trait screening among African Americans within middle reproductive age

OBJECTIVE

This study examined the meaning of sickle cell trait and sickle cell trait screening from the lay perspective of African Americans.

DESIGN AND METHODS

African Americans (N = 300), ages 18-35 and unaware of their sickle cell trait status, completed two open-ended questions from a larger survey. One question asked for their understanding of sickle cell trait; the other asked for their understanding of sickle cell trait screening. Content analysis occurred in two phases: (1) In vivo and holistic coding; and (2) focused coding.

RESULTS

Four categories emerged illustrating lay conceptions of sickle cell trait; (1) Perceived as an illness; (2) Perceived recognition of the inheritance pattern of sickle cell trait; (3) Perceived lack of knowledge of sickle cell trait; and (4) Perceived importance of sickle cell trait. Five categories emerged illustrating lay conceptions for sickle cell trait screening: (1) Perceived recognition that screening means getting tested for sickle cell trait; (2) Perceived lack of knowledge of sickle cell trait screening; (3) Perceived health benefit of sickle cell trait screening; (4) Perceived importance of sickle cell trait screening; and (5) Perceived barriers to sickle cell trait screening.

CONCLUSIONS

Sickle cell trait and sickle cell trait screening are concepts that are both regarded as important among this high-risk population. However, there is still misunderstanding concerning the hereditary nature and reproductive implications of sickle cell trait. Interventions seeking to improve communication on the need for sickle cell trait screening should begin by identifying what the population at large understands, knows and/or believes to improve their ability to make informed health decisions.