Genomics in Public Health Nursing



Genomics in Public Health Nursing



“Mapping the human genome is the outstanding achievement not only of our lifetime but in human history. This code is the essence of mankind, and as long as humans exist, this code is going to be important and will be used.”


T. Michael Dexter


Objectives


After reading this chapter, the student should be able to do the following:



KEY TERMS


DNA, p. 244


family health history, p. 249


genes, p. 244


genome, p. 242


genomics, p. 242


genetics, p. 242


genetic susceptibility, p. 249


Human Genome Project, p. 243


multifactorial diseases, p. 246


mutations, p. 244


–See Glossary for definitions


imageElke Jones Zschaebitz, MSN, FNP


Elke Jones Zschaebitz has been a nurse practitioner since 1998 and has worked in the fields of school health, pediatrics and women’s health, as well as telehealth practice in primary care. She has also been involved in issues of rurality, poverty, and primary care. A former instructor of nursing at the University of Virginia. School of Nursing and the UVA College at Wise for the Healthy Appalachia Institute, Zschaebitz was also in clinical practice at UVA High Risk Breast and Ovarian Cancer Center, working closely with families with a genetic or familial predisposition to breast and ovarian cancer.


imageJeanette Lancaster, PhD, RN, FAAN


Jeanette Lancaster has co-edited the previous seven editions of this textbook with Dr. Marcia Stanhope. This edition adds some new and timely chapters, including this one on genomics and its role in nursing, particularly public health nursing. Dr. Lancaster is the Medical Center Professor of Nursing at the University of Virginia, Charlottesville, VA.


Special thanks are given to Gia Mudd, RN, MPH, PhD, Assistant Professor, College of Nursing, University of Kentucky for reviewing the manuscript, providing public health nursing input, and providing two of the case examples.



The Human Genome and its Transforming Effect on Public Health


The mapping of the human genome was a strategic inflection point in the history of health care that created a massive shift in how all health professionals deliver care and how public health will be approached. The understanding of the fundamental role genetics and genomics will play in shaping the practice of public health nurses in the twenty-first century is in its early stages, although the rate of new knowledge is incredible. This chapter discusses the history of the field of genetics and genomics, what we know about genetics and genomics now, their impact on current nursing practice, and the prospects for significant changes in how nursing care is delivered. Clearly, nursing will be dramatically altered by new discoveries in molecular genetics. Examples of the effect on nursing include: (1) how nursing students will be educated, (2) how nurses will collect and use health histories, (3) how nurses will learn and apply innovative biotechnology, (4) the role genetics and genomics will play in traditional nursing arenas such as prevention and health education, (5) the administration of new therapies, and (6) in public health debates including the moral, ethical, legal, and social issues around this powerful new field of knowledge.


It is important to recognize that the fields of genetics and genomics are emerging, extremely complex, and ever changing. They have enormous implications for the detection, prevention, and treatment of human disease, not to mention educational and economic development. There is an explosion of new possibilities, such as in the prevention and treatment of human maladies ranging from cancer to cystic fibrosis and from autism to Alzheimer’s disease. To understand the effects of this knowledge in public health and in nursing, it is important to pull key snapshots from this highly detailed landscape in order to begin to describe this new territory that nursing practice occupies. This chapter provides an overview of the history of the development of this new science and briefly discusses the current state of the science of genetics and genomics in relation to the role of the nurse and the future implications for care of individuals, families, and populations. What is clear is that every nurse needs to rapidly become knowledgeable about genetics and genomics and their effects on populations.


In this chapter, the term genetics refers to the study of the function and effect of single genes that are inherited by children from their parents. Genomics is the study of all of a person’s genes including their interaction with one another, as well as the interaction of a person’s genes with the environment. Genomics examines the molecular mechanisms and the interplay of genetic and environmental, and of cultural and psychosocial, factors in disease. Genomics deals with the functions and interactions of all genes in an organism and is the study of the total DNA structure (Perry, 2011).


A Brief History of the Science



“The problem [with genetic research] is we’re just starting down this path, feeling our way in the dark. We have a small lantern in the form of a gene, but the lantern doesn’t penetrate more than a couple of hundred feet. We don’t know whether we’re going to encounter chasms, rock walls or mountain ranges along the way. We don’t even know how long the path is…”


Francis Collins


It is important to understand the evolution of genetic and genomic knowledge. The concept of this hereditary information began with agriculture in the eighteenth century by Gregor Mendel, an Austrian monk who is usually considered to be the father of genetics. At about the same time, Charles Darwin expounded on these theories of evolution, and Darwin’s cousin, Francis Galton, performed family studies using twins in an effort to understand the influence of heredity on various human characteristics.


A major breakthrough occurred on February 28, 1953 in Cambridge, England when James Watson and Francis Crick announced that they had figured out the structure of deoxyribonucleic acid (DNA), and that this double-helix structure could unzip to make copies of itself—thus confirming that DNA carries life’s hereditary information, or the secret to life (McKusick, 2007). H.J. Muller later demonstrated the genetic consequences of ionizing radiation on the fruit fly, and the theoretical basis of population genetics was developed by three prominent individuals: Ronald Fisher, J.B.S. Haldane, and Sewall Wright. Genetic diseases and their mode of inherited anomalies such as phenylketonuria, sickle cell disease, Huntington’s disease, and cystic fibrosis were established. In the same decade that Watson and Crick discovered DNA, the correct specification of the number of human chromosomes was determined. Because of this 1956 discovery, for instance, one of the new findings in genetics included the discovery in 1959 that Down syndrome is caused by an extra copy of chromosome 21. The scientific revolution was underway.


To date, the Human Genome Project (HGP), an international research project funded by the U.S. Congress in 1988 and completed in 2003, has mapped all of the approximately 25,000 genes in human DNA. This enormous project reflects the work of scientists from 20 research centers in six countries: China, France, Germany, Japan, the United Kingdom, and the United States (Feetham, Thompson, and Hinshaw, 2005). The stated goals of the HGP were: determining the sequences of the 3 billion chemical base pairs that make up human DNA; storing this information in databases; improving tools for data analysis; transferring related technologies to the private sector; and addressing the ethical, legal, and social issues (ELSI) that may arise. The director of the Project was Francis Collins, MD. Dr. Collins and his team developed a conceptual vision for their work that had three overarching themes:



Interestingly, two key findings from early work to sequence the human genome were that all humans are 99.9% identical at the DNA level and nearly 25,000 genes make up the human genome (Perry, 2011). Most of the 0.1% genetic variations are found within and not among populations. These findings have implications for public health with its emphasis on population health.



DID YOU KNOW?


Francis Collins, who directed the HGP, compared the project to a book that had many different uses. He said, “It’s a history book: a narrative of the journal of our species through time. It’s a shop manual, with an incredibly detailed blueprint for building every human cell. And it’s a transformative book of medicine, with insights that will give healthcare providers immense new powers to treat, prevent, and cure disease” (Collins, 2006, p 1).


Many implications for health care have emerged from this project, including ethical and moral dilemmas that continue to be challenging. As health information advances, genomics has influenced the availability of genetic tests. Many of these tests have implications for families and it is in nursing’s best interest that individuals and communities understand the purpose, limitations, potential benefits, and potential risks of a test before submitting samples for analysis. The issues of genetic screening and prophylactic treatments alone are staggering and will require the full resources of the nursing profession to find answers.





WHAT DO YOU THINK?


A Case Example: Screening for Breast or Ovarian Cancer Risk


During an initial visit to the High Risk Breast and Ovarian Cancer Clinic, a 37-year-old, Ms. Brown, reports that she had found a mass during a self-breast examination in 2006. She subsequently had the mass inspected by a clinician and underwent a mammogram, which showed a suspicious finding. A breast core-biopsy was performed and the pathology report indicated that she had atypical ductal hyperplasia. Ms. Brown then had a breast lumpectomy, and the lump was benign. In 1996, she had undergone a total abdominal hysterectomy and bilateral salpingo-oophorectomy for endometriosis. Ms. Brown briefly took hormone replacement therapy but stopped in 2006 when the breast mass was identified. She initiated Evista therapy as a breast cancer reduction measure, but after 6 months she stopped the medication because of the side effects. Ms. Brown reports that she is not entirely opposed to considering using Evista again. Her family history indicated that a paternal grandmother likely had a type of “female cancer.” This grandmother died in her middle 30s to early 40s. There were also three cousins on the paternal side of the family who had unilateral breast cancer when they were in their 30 and 40s.


On the maternal side of the family, her grandmother was diagnosed with breast cancer when she was in her 40s. She is alive and doing well at age 72. One of the grandmother’s sisters had lymphoma and died in her late 60s. A maternal great-aunt who was a sister to her maternal grandfather, not maternal grandmother, died in her 70s of ovarian cancer. A sister to her maternal great-aunt (another maternal great-aunt) died in her 70s or 80s of a primary brain cancer.


Reflect on these questions and see what implications they have for nursing action and for public health concerns:



Over 180,000 new cases of breast cancer are diagnosed annually, and between 5% and 10% of them have an inherited susceptibility. It is important for the nurse to take a brief family pedigree as done above to identify inherited risk factors. If Ms. Brown were to have had a BRCA-1 or BRCA-2 mutation, many more implications for decision making would arise, including prophylactic surgery for prevention of breast and/or ovarian cancer. In addition, men with a BRCA-1 mutation are at increased risk to develop prostate cancer or colorectal cancer. Men who have the BRCA-2 mutation are at risk for male breast cancer and pancreatic cancer. For women, both BRCA-1 and BRCA-2 mutation carriers have the greatest risk for breast and ovarian cancer. It is important when interpreting genetic information to be sensitive to the many issues involved, including emotional, socioeconomic, lifestyle, and environmental issues that may affect the onset of disease (Calzone et al, 2010).


DNA and its Relationship to Genomics and Genetics


At the core of the issues related to genetics and genomics is deoxyribonucleic acid (DNA). The structure of DNA is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. DNA is the chemical inside the nucleus of a cell that has the genetic instructions for making living organisms. DNA can be compared to a long-term storage or a blueprint or code to construct other components of cells such as proteins and ribonucleic acid (RNA) molecules. The DNA segments that carry the genetic information are called genes. Within cells, DNA is organized into long structures called chromosomes. These chromosomes are duplicated before cells divide, in a process called DNA replication. DNA is comprised of four bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Genes are comprised of specific sequences of these bases.


Alterations in the usual sequence of bases that form a gene or changes in DNA or chromosomal structures are called mutations. A large number of agents are known to cause mutations (Jorde, Carey, and Bamshad, 2010). These mutations, which are attributed to known environmental causes, can be contrasted with spontaneous mutations, which arise naturally during the process of DNA replication. Approximately 3 billion DNA base pairs must be replicated in each cell division, and considering the large number of mutagens to which we are exposed, DNA replication is fascinatingly accurate (Jorde, Carey, and Bamshad, 2010). A key reason for this accuracy is a mechanism called DNA repair, which occurs in all normal cells of higher organisms. It is estimated that repair mechanisms correct at least 99.9% of initial errors.



DID YOU KNOW?


For a person living in a developed country, a typical lifetime exposure to ionizing radon is about 7 Radon Environmental Monitoring (REM), a standard unit for measuring radiation exposure. About one third to one half of this amount is thought to originate from medical and dental x-ray procedures.


Hundreds of chemicals are now known to be mutagenic in laboratory animals. Among these are nitrogen mustard, vinyl chloride, alkylating agents, formaldehyde, sodium nitrite, and saccharin. In addition, ionizing radiation, such as those produced by x-rays and from nuclear fallout, can promote chemical reactions that change DNA bases or break the bonds of double-stranded DNA.


So what does an understanding of DNA and the science of genetics have to do with public health nursing? In essence, this brief history of the field of genetics shows that human disease comes from the collision between genetic variations and environmental factors. As knowledge has evolved with the mapping of the human genome, our understanding of this interaction continues to advance. This has increased knowledge about disease prevention and new methodologies for the practice of public health. We are learning to integrate more effectively our understanding of biological determinism within a social context.



The Challenges of Genetic and DNA Testing


Tests are now available to evaluate for more than 1600 genetic disorders ranging from single-gene disorders, such as cystic fibrosis, to more complex disorders, such as diabetes (Calzone, Cashion, and Feetham, 2010). As will be discussed in a later section of the chapter, taking a family history is a useful place to begin when considering a genetic connection and prior to the onset of testing.


DNA testing was first used in the late 1970s; today, the indications for a DNA test have expanded to include predicting the development of genetic disorders, screening populations, confirming clinical diagnoses, prenatal testing, and DNA testing to develop and apply individualized medical treatment. The next few years will see an explosion in the number of DNA tests driven by information generated from the HGP. Improved technology will make DNA testing more accessible. These advances in genetics/genomics will necessitate that nurses continue to learn about this area of science in order to respond effectively to the challenges of this new knowledge.


An example of this challenge is that of genetic testing for mutations associated with a hereditary cancer syndrome. The best way to identify whether there is a mutation in a family where a hereditary cancer syndrome is suspected is to test the person who displays the most evidence of being a mutation carrier. This is usually a relative who has had a cancer that occurs typically as part of the hereditary cancer syndrome (e.g., breast or ovarian) that is suspected in the family.


The above example could present a difficulty because family members who have had cancer may not agree to being tested for genetic mutations. This refusal presents challenges to the person who desires information that might affect decision making and his or her health. An additional difficulty is that some individuals do not have an insurance carrier that reimburses for genetic testing, or they may have a high deductible in the insurance policy. Some individuals also think that testing will decrease the quality of their life and make them anxious about the future if they were to discover they have a mutation. Other people fear a positive test result may lead to feelings of guilt about passing along a disease to children and grandchildren.


Case 1


K.N. is a 42-year-old mother with three daughters, ages 16, 18, and 22. She has an extensive family history of ovarian cancer. Because of her family history, K.N. is regularly screened per current treatment guidelines. K.N.’s mother, who was diagnosed with ovarian cancer at age 55, underwent genetic testing and was discovered to be a carrier of the BRCA-2 gene mutation predisposing to breast and ovarian cancer. Despite undergoing frequent screening, several of K.N.’s aunts have died of ovarian cancer at an early age. K.N.’s husband wants her to be tested for the BRCA-2 gene and, if positive, has encouraged her to undergo a prophylactic salpingo-oophorectomy. K.N. is concerned that a positive genetic test may result in loss of insurance coverage. She is also concerned that this will have a negative psychological impact on her children.


Joan Akins is a public health nurse at the county health department serving the area where K.N. resides. Ms. Akins has recently conducted a cancer awareness campaign that included public health education on hereditary cancer syndromes. K.N. contacts Ms. Akins to request advice on whether to undergo genetic testing. Ms. Akins actively listens to K.N.’s concerns and provides general information on genetic testing and the implications of the test results for K.N. and for her children. She also discusses the newly enacted Genetic Information Nondiscrimination Act (GINA) legislation that protects the public from genetic discrimination by employers and insurers. Ms. Akins encourages K.N. to talk with her gynecologist about her concerns and to make an appointment for genetic counseling, providing names and contact information for local genetic counselors who specialize in cancer genetics.


As mentioned, genetic testing decisions are personal and complex and can be controversial, leading to dissonance in families. It is important for public health nurses to respect individuals’ and family members’ decision-making processes. They must, at the same time, be well informed about genetic testing to provide accurate education to members of the public in order to support appropriate decision making.


Also, current methods of testing do not detect all of the mutations that can occur in some diseases, including hereditary cancer syndrome-related genes. If a mutation is detected during DNA testing, this would not confirm an absolute risk for cancer, but rather would indicate that a person is at increased risk to develop the cancers that are part of the particular hereditary cancer syndrome and may need high-risk management. Such a finding has implications for family members who might have inherited the same mutation, enabling them to undergo DNA testing specific to the identified mutation. Such focused testing is more accurate and cost-effective than testing for multiple potential mutations (NCI, 2010). In contrast, if DNA testing in a cancer-effected relative is negative, this does not indicate family members are not at risk. There might be a mutation in a different hereditary cancer syndrome gene than those tested. It is important to remember that many mutations associated with cancer susceptibility and familial syndromes have yet to be identified.


For these reasons, family history must also be considered. However, caution is needed in interpreting family history for several reasons: an inherited syndrome may not be evident for someone with a small family; not everyone is informed of their family’s history of disease; death of a family member may be unrelated to cancer, such as early accidental death; or members may have been adopted and this may not be known to others in the family. Finally, because most cancers are not hereditary, family history should be accompanied by assessment of shared familial environments.


Case 2


Sickle cell anemia is an autosomal recessive disease in which a gene mutation results in the production of structurally abnormal hemoglobin, called hemoglobin S. Gene carriers have one normal form of the hemoglobin gene and one mutation, a condition called sickle cell trait. The highest rates of disease are among African Americans, with sickle cell anemia affecting approximately 1 in 500 African Americans and 8% of the population being carriers (anemia, sickle, National Center for Biotechnology Information [n.d.] (See http://www.ncbi.nlm.nih.gov/books/NBK22238.)


Marge Covington is a public health nurse employed by a non-profit, community-based organization that provides health care education and outreach services to members of the African American community in a large metropolitan area. The rate of sickle cell anemia among members of the community is higher than the national average. In response, Ms. Covington has implemented a program with the projected outcome to reduce disease rates among African Americans in the community. The program objectives are to: (1) increase awareness of the disease in the community, and (2) increase rates of carrier testing to support informed decision making regarding childbearing. To meet these objectives, Ms. Covington has initiated monthly educational sessions on sickle cell anemia and sickle cell trait at community centers throughout the area. She has also collaborated with a local hospital system to provide free bi-annual genetic counseling sessions with optional carrier screening at community health clinics.


Continuing education is important for public health nurses during this time of rapid integration of new genetic tests into health care practice. Only through ongoing education will public health nurses have the basis from which to appropriately educate the public regarding genetic testing. In addition, recognition of the role of gene-environment interactions in susceptibility to cancer and many other diseases underscores the importance of assessing risk from an environmental perspective. Public health nurses offer this perspective as part of the larger interprofessional team needed to address the complex issues involved in genetic testing.


Current Issues in Genomics and Genetics


Many issues are involved in the growing field of genetics/genomics. Selected issues will be briefly discussed here. Currently the public is not fully aware of the importance of having a family medical history. Also, many health care providers are not entirely clear about how to interpret family history of a client who has had the initiative to collect it. In addition, many clients are still reluctant to disclose this family history for fear that it would affect their health insurance status or eligibility despite current laws in place designed to protect these clients.


Another issue is a key one for public health nurses. If clients are expected to make lifestyle changes based on information about their genetic risk factors, the appropriate support and education should be available to clients and families. Nurses play an important role in answering questions and assisting in challenges these clients and families face with making decisions when there is any suspicion of increased risk for genetically based diseases. To make things more confusing, many pharmaceutical companies have begun to market their tests and advertise directly to the public. This type of marketing has implications for nurses and other health care providers who need to provide the appropriate counseling about the implications and indications for such testing. For example, marketing on the Internet complicates client decision making since it can provide consumers with easy access to genetic tests without involving a health care professional in the testing process. Even the clinically available genetic tests, which may provide legitimate test results, are difficult to interpret without genetic counseling. Currently, the Centers for Disease Control and Prevention (CDC), the Centers for Medicare Services (CMS), and the Federal Drug Administration (FDA) have oversight of genetic tests and products, whereas the Federal Trade Commission (FTC) has oversight of the advertising of these tests and products. The National Institutes of Health (NIH), Health Resources and Services Administration (HRSA), and Agency for Healthcare Research and Quality (AHRQ) support research related to genetic tests and products.


Many factors acting together typically influence disease risk, health conditions, and the therapies used to treat disease. These risks, conditions, and diseases often have a genetic/genomic element that is influenced by the environment, lifestyle, and other factors. These are considered multifactorial influences. Multifactorial disorders tend to occur in families (Perry, 2011). For example, “common congenital malformations, such as cleft lip and palate and neural tube defects, result from multifactorial inheritance, a combination of genetic and environmental factors” (Perry, 2011, p 147). Box 11-1 presents examples of multifactorial diseases, or those caused by gene and environment interaction.


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Apr 2, 2017 | Posted by in NURSING | Comments Off on Genomics in Public Health Nursing

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