Progress in the field of genetics has moved at breakneck speed since the discovery of the structure of DNA in 1953. At that time, no human disease had been connected to our chromosomes or DNA. More than 50 years later, starting with the completion of the human genome project, the pace of discovery has only accelerated, moving quickly out of research into the clinic. Traditionally, diseases involving DNA were in the domain of genetics experts. But now, as the underpinnings of more and more conditions can be traced back to our genetic code, few fields of medicine can avoid this genomic revolution.
With revolutions and rapid change come challenges. Medical school curricula are still catching up with genomic medicine, and practicing physicians and other health professionals are left to educate themselves. Recalling our own training, we realized that students and residents don't read huge textbooks, but rather gravitate toward high yield, efficient, practical material. Unable to find such a guide for genomic and precision medicine, we endeavored to write it ourselves.
Providing a comprehensive overview of the practice of genomic medicine while keeping the material tight and concise was not simple and we struggled mightily to achieve the ideal scope in this handbook. There is a reason why existing texts are tomes: genomic knowledge is expansive. Therefore, this book is not intended for the genetics expert, nor does it provide a complete background in biology for a beginner. Rather, this text is intended for general health care practitioners and trainees (primary care, hospitalist, residents, nurses, and students in these and related disciplines) with two goals. First, the book offers detailed guidance on many applications of genomic medicine that have already penetrated nonspecialty medical care. Second, it provides background and practical knowledge on current and imminent technologies and concepts that will enhance a health care provider's confidence and efficiency when interacting with specialists, specialty tests, and informed patients. Throughout, we strive to highlight common pitfalls—technical and ethical—that might complicate the provision of quality genomic medical care. The emphasis is always on real-life patient interactions and decision support, though the reader must be cautioned that practices both vary and evolve and there are few simplicities.
Also for the sake of brevity, this text is necessarily selective about which aspects of genomic and precision medicine are considered. Many readers may find a specific topic inadequately addressed. For more in-depth information on a specific test or topic, we provide resources that can be consulted. We encourage feedback for future editions of the book. Our emphases for this inaugural edition are applications of genomic medicine that are common, commonly misunderstood, or involve recent technological innovations.
This book is divided by life stages, beginning before conception through adulthood. Several appendices detail subjects that span these categories, such as diagnostic technology, ethical issues, and the nuts-and-bolts of ordering tests. A pediatrician, for example, may be tempted to read only those chapters that pertain to children, but we would humbly suggest that he read the entire text. Important, common threads weave together the application of precision medicine at every life stage and inform each other.
A common theme in the coming chapters is a sea change in the practice of clinical genetics. In the past, eligibility for genetic testing was carefully calculated and such testing was only offered to clearly defined patients, usually because of a quantifiable risk (advanced maternal age, family history, etc.). This approach is eroding, replaced by a more consumer-driven model by which patients are considered to be entitled to whatever genomic information they desire, with the health care practitioner as a partner rather than a gatekeeper. Payers are also struggling to keep up with advancing technology and challenges with reimbursement abound.
The most extreme form of genetic accessibility is direct-to-consumer genomic testing, which is discussed further in Chapter 11. The wisdom and cost-effectiveness of this new approach will be the subject of debate for years to come. Even within the realm of physician-ordered testing, the emphasis has clearly shifted from deciding if a patient should get testing, to ensuring that testing is appropriately, consistently, and accurately applied and interpreted. The practice of Genomic and Precision medicine has not yet succeeded in achieving this objective, and this text is part of a larger effort to equip the nongeneticist practitioner with the background to apply genomic technology responsibly and for the betterment of patients.
If we could provide one piece of advice for anyone diving into the world of Genomic and Precision medicine for the first time: be skeptical but excited. Meet the skepticism with ambition to learn more, not avoidance or paralysis. Balance the excitement with a determination to provide the highest quality and evidence-based care possible, not an immediate acceptance of everything new. Within this equilibrium, the application of precision medicine can be of benefit to patients and providers alike.