Primer on medical genomics. Part VIII: Essentials of medical genetics for the practicing physician

Genomics Basics: DNA Structure, Gene Expression, Cloning, Genetic Mapping, and Molecular Tests

Genomics is the study of the structure and function of the human genome including genes and their surrounding DNA sequences. The over 3 billion base pairs of the human genome have now been sequenced and approximately 25 000 genes acknowledged. However, only 1% of the entire genome has been assigned to protein coding and decades more work is anticipated to define the functional relevance of noncoding DNA as well as the basis and consequences of sequence variations among individuals. For medical scientists, the focus remains on discovering both disease-causing and disease-susceptibility genes. For pharmaceutical companies, the opportunity to develop molecularly targeted therapy is not going unnoticed. For the practicing physician, the prospect of genomic medicine that incorporates molecular diagnosis and pathogenesis-targeted therapy requires basic understanding of terminology and concepts in molecular biology and the corresponding laboratory tests.

Migraine genetics--a review: Part I

Significant progress in molecular genetics has advanced our understanding of the genetic basis of migraine. The fundamentals of molecular genetics, and the recent advances in the field, are important for clinicians to understand, as they provide a foundation for critical appraisal of the literature, unprecedented insights into the pathogenesis of the disorder, and reveal promising treatment targets for future drug development. This paper provides a primer of molecular genetics and will be followed by a companion paper on the genetic advances in migraine, the methodology of genome wide association studies, and the potential clinical implications.

Improving risk assessment in family medicine through the family history

The family history is used as a screening tool to identify persons who may be at risk for a heritable disorder. Primary care providers sometimes do not thoroughly gather and document the family history. This pilot study was undertaken to determine whether having a genetic counselor on site at our family medicine clinic 2 days a week for 3 months would improve the quality of the family history field in patient records. We compared 7 elements in the family history field for patients seen before and after the genetic counselor was on site. Documentation of 1 of the 7 elements (major disease) improved significantly after the intervention period (P = .02). Changing provider behavior with regard to gathering and documenting family history of major disease may be facilitated by tools to help collect the family history and by using the increasing number of available genetic tests.

Mutation spectrum of 122 hemophilia A families from Taiwanese population by LD-PCR, DHPLC, multiplex PCR and evaluating the clinical application of HRM

Background

Hemophilia A represents the most common and severe inherited hemorrhagic disorder. It is caused by mutations in the F8 gene, which leads to a deficiency or dysfunctional factor VIII protein, an essential cofactor in the factor X activation complex.

Methods

We used long-distance polymerase chain reaction and denaturing high performance liquid chromatography for mutation scanning of the F8 gene. We designed the competitive multiplex PCR to identify the carrier with exonal deletions. In order to facilitate throughput and minimize the cost of mutation scanning, we also evaluated a new mutation scanning technique, high resolution melting analysis (HRM), as an alternative screening method.

Results

We presented the results of detailed screening of 122 Taiwanese families with hemophilia A and reported twenty-nine novel mutations. There was one family identified with whole exons deletion, and the carriers were successfully recognized by multiplex PCR. By HRM, the different melting curve patterns were easily identified in 25 out of 28 cases (89%) and 15 out of 15 (100%) carriers. The sensitivity was 93 % (40/43). The overall mutation detection rate of hemophilia A was 100% in this study.

Conclusion

We proposed a diagnostic strategy for hemophilia A genetic diagnosis. We consider HRM as a powerful screening tool that would provide us with a more cost-effective protocol for hemophilia A mutation identification.

Cancer genetics: consultants' perceptions of their roles, confidence and satisfaction with knowledge

RATIONALE, AIMS AND OBJECTIVES

Genetic testing for susceptibility for common cancers is widely available. Cancer specialists and specialists in other areas may have a role in identifying and referring patients who would benefit from a consultation with a specialist in genetics. This study aimed to find out which consultants believed that genetic testing was relevant to their practice. We also wanted to determine their views of their roles in relation to genetic testing, their confidence in these roles, and the value of different educational tools.

METHODS

This was a self-completed, cross-sectional, postal survey of all the consultants in Northern Ireland (n=520, response rate=59.3%) identified from the Central Services Agency list.

RESULTS

Three hundred and ninety questionnaires were returned (44%). A total of 28.6% did not complete the questionnaire stating that genetics was not relevant to their practice. Few consultants reported having consultations related to genetic disease, receiving training in genetics and referring to genetics services. There was some dissatisfaction with their current knowledge of genetics and they believed that guidelines and educational tools may be useful. The respondents lacked confidence in undertaking some of their roles. Through their responses to the cancer scenarios, these consultants showed that they would offer appropriate advice and referrals. Many consultants did not know if family history information should be provided to insurance companies.

CONCLUSIONS

Some consultants may require further training to enable them to fulfil their roles in relation to genetics. Tools or guidelines to assist with referral decisions may also be useful. Consultants may need clearer guidance regarding the provision of family history information to insurance companies.

Cancer Genetics

OBJECTIVES

To provide a basic overview of genetics, focusing on breast and ovarian cancer susceptibility mutations on BRCA1 and BRCA2.

DATA SOURCES

Research and review articles and government internet sites.

CONCLUSION

The advances in molecular biology has enabled health care providers to be proactive rather than reactive in predicting some cancers and offering prevention strategies to greatly reduce the risk of developing cancer. Our expanding knowledge base of genetics may one day provide tailored treatment, and predict recurrence rates for all cancers.

IMPLICATIONS FOR NURSING PRACTICE

The science of genetics will impact every aspect of health care, from primary care to specialized care. Nurses are on the front line and will be expected to recognize patterns of disease that may indicate a possible genetic link, educate the family about the implications of a potential genetic susceptibility and refer the family for counseling. To accomplish this, each nurse should have a minimum basic knowledge of genetics, and formal education for those who educate and counsel.

Preconception healthcare: what women know and believe

OBJECTIVES

The objectives of this study were to determine if women realize the importance of optimizing their health prior to a pregnancy, whether the pregnancy is planned or not; and to evaluate their knowledge level and beliefs about preconception healthcare. Additionally, we sought to understand how and when women wanted to receive information on preconception health.

METHODS

A survey study was performed using consecutive patients presenting to primary care practices for an annual well-woman exam. Patients were recruited based on appointment type and willingness to complete the survey at the time of their appointment, but prior to being seen by the physician.

RESULTS

A total of 499 women completed the survey. Nearly all women (98.6%) realized the importance of optimizing their health prior to a pregnancy, and realized the best time to receive information about preconception health is before conception. The vast majority of patients surveyed (95.3%) preferred to receive information about preconception health from their primary care physician. Only 39% of women could recall their physician ever discussing this topic. The population studied revealed some significant knowledge deficiencies about factors that may threaten the health of mother or fetus.

CONCLUSIONS

A majority of women do understand the importance of optimizing their health prior to conception, and look to their Primary care physician as their preferred source for such information. Study participants demonstrated deficiencies in their knowledge of risk factors that impact maternal and fetal health suggesting that physicians are not addressing preconception healthcare during routine care.

Hemophilia: a practical approach to genetic testing

Hemophilia and von Willebrand disease together account for the large majority of congenital bleeding disorders. Contemporary management, including development of safer clotting factor concentrates and increased emphasis on long-term follow-up in comprehensive hemophilia centers, has improved both quality of life and longevity for patients with congenital bleeding disorders. In addition to facilitating development of recombinant clotting factor concentrates, isolation and characterization of the respective genes have led to increasing availability of a repertoire of genetic tests that, although expensive, are critical for appropriate genetic counseling of affected patients and their family members. This article provides a practical approach to using genetic testing for hemophilia A and B.

Genetic testing: practical, ethical, and counseling considerations

Genetic testing is becoming a much more common practice in medicine today. This presents a unique set of challenges for medical professionals in virtually all specialties. The practical aspects of determining which test to order, and in interpreting the result accurately in the context of the family history, can be difficult. Additionally, the ethical conundrums that frequently present themselves when genetic risk assessment and/or genetic testing is being considered can be daunting. These challenges present real concerns for medical professionals and patients alike. Included in this article is a review of some of the practical and ethical complexities associated with genetic testing. Pretest and posttest genetic counseling is also emphasized as an important and essential process in today's medical practice.

Gene Testing: What the Health Professional Needs to Know

Physicians and health professionals are faced with new challenges in the era of increasing information on genetics and health. The sequencing of the human genome has created more opportunities for genetic research and increased awareness of the role of genes in diseases. There is also an increased awareness of genetic susceptibility and gene testing. As a result of the advances in genetic research, the public demand for gene testing is on the rise. Patients are now seeking more information about inheritable diseases and predisposition to genetically related disease from doctors and other health professionals. Genetic tests are often conducted to confirm the diagnosis of a genetic disease as well as to assess genetic risk, predict response to drugs, and assist in reproductive decision making. Genetic tests are available for over 950 inherited diseases or conditions in the GeneTests data base for clinical or research purposes. A number of challenges face health professionals when using genetic tests for diagnosis, predictive testing, or reproductive decision making. These include the constant change in genetics knowledge and the increased demand to keep up with the various aspects of the genetic testing process. To meet these demands, physicians and other health professionals should use available educational genetic resources to provide adequate patient care.