Journal Publication

The Intersection of Genetics, Public Health, and Preventive Medicine

Steven S. Coughlin, PhD, MPH, Guest Editor 

This issue of the journal features several articles that explore the intersection of genetics, public health, and preventive medicine. The topics considered include genetic aspects of several illnesses, including coronary heart disease, hemochromatosis, breast cancer, colorectal cancer, Alzheimer disease, and HIV infection, illnesses that compromise quality of life and strain public health. Ethical, legal, and social issues that arise from genetic testing and screening of newborns and adults are also described. These articles provide an update on important topics in genetics for physicians who are practicing preventive medicine and for other public health professionals.

Preventive medicine and public health have traditionally focused on modifiable risk factors for disease such as cigarette smoking, alcohol consumption, obesity, physical inactivity, and high-risk sexual practices; on preventive interventions such as immunization; and on screening for disease precursors such as hypercholesterolemia, hypertension, and cervical dysplasia.^1-4 Such risk factors and precursors for disease usually become apparent in adolescence or later in life and are often amenable to preventive interventions. Genetic factors, on the other hand, have been viewed as intransigent, immutable, and innate. How, then, can genetics, public health, and preventive medicine intersect?

One answer is that genetic testing and screening sometime allow for the identification of a genetic condition or predisposition before the onset of clinically recognized, irreversible disease.^5,6 Screening for phenylketonuria (PKU) in newborns, for example, can detect the condition for which a preventive intervention is available. Nevertheless, scientifically rigorous evaluations of the effectiveness of newborn screening, discussed by Richard Olney in this issue of the journal, is needed for metabolic and hematologic disorders. Evidence that screening for a genetic trait or mutation and providing early intervention or treatment results in improved prognosis and favorable health outcomes should come from randomized trials.⁷

Interest is broadening beyond single-gene disorders evident in childhood (such as sickle cell disease and PKU) to the genetic basis of common, adult-onset disorders that cause substantial morbidity and mortality.⁸ Examples of such genetic disorders in this issue of the journal include mutations to the hMSH2 and hMLH1 genes as causes of susceptibility to colorectal cancer, associations between factor V Leiden and thromboembolic disorders, an association between the APOE E4 allele and late-onset Alzheimer disease, and the identification of the HFE gene for hemochromatosis.

Genetic screening for these adult-onset disorders is not recommended at present, outside of high-risk families and research protocols. An increasing number of genetic tests are being marketed directly to physicians and patients, however, and many patients are seeking access to such tests.^9,10 An example of this occurrence is the introduction of tests for BRCA1 gene mutations and susceptibility to breast and ovarian cancer. Genetic testing is being introduced into some clinical practice even before the risks and potential benefits are sufficiently understood and adequate measures are taken to ensure the safety and effectiveness of the testing. The potential for discrimination and the need for adequate informed consent and pre- and post-test genetic counseling are discussed by Ellen Clayton in relation to newborn screening and by Stephen Post in relation to genetic testing for Alzheimer disease.

Genetics, public health, and preventive medicine also intersect in an emerging paradigm of disease prevention--the identification and modification of environmental risk factors among persons susceptible to disease due to genotype.^{6, 11} For example, genetic testing for childhood asthma may improve the predictive value of environmental factors such as allergens and secondhand exposure to cigarette smoke. The identification of gene-environment interactions in the etiology of osteoporosis could result in preventive and therapeutic interventions for middle-aged persons at risk for later complications of the disease.¹² For example, interactions might be identified between candidate genes for osteoporosis and non-genetic factors such as low calcium intake, vitamin D deficiency, and physical inactivity. Tests for other genetic conditions may allow for the identification of subgroups of patients who are more or less likely to benefit from preventive strategies such as the use of cholesterol lowering drugs and replacement estrogens.

In the near future, the identification of genotype through genetic screening might allow for the identification of persons truly at high risk for an illness, targeted medical interventions, and improved allocation of health care resources. Physicians who practice preventive medicine will need to keep abreast of developments in genetic testing and screening so that they can provide information to their patients, contribute to the appropriate use of such testing, and help guard against inappropriate use. Thus, the introduction of new genetic technologies in public health and clinical medicine will require continuing professional education opportunities for physicians and other health professionals.¹³ The need to address technologic and quality assurance challenges in large-scale genetic testing and screening will continue, as will important ethical, legal, and social concerns.^{13, 14} I look forward to continuing discussion of these issues in the pages of the American Journal of Preventive Medicine.

Address for correspondence: Epidemiology and Health Services Research Branch, Division of Cancer Prevention and Control, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, 4770 Buford Highway, NE (K-55), Atlanta, GA 30341, E-mail SIC9@CDC.gov.

References

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