The general practitioner and the "new genetics"

Linda Mann
Med J Aust 2003; 179 (2): 109-111. || doi: 10.5694/j.1326-5377.2003.tb05449.x
Published online: 21 July 2003


  • GPs are involved in long term care of patients and families with complex conditions. They juggle the need for medical expertise, the relationships between family members, the cost of expertise, limitations of access, and the medicolegal environment. With this background, the GP is ideally placed to play an active role in the "new genetics".

  • GP consultations involving the new genetics will include diagnostic testing for patients with clinical problems, preconception and prenatal testing for couples in relation to pregnancy, predictive testing for families with some genetic conditions, and community genetic screening in some circumstances.

  • GPs will need to understand the language of the new genetics, undergo continuing education, and receive ongoing support to enable them to communicate effectively with patients and their families.

  • Different models of care incorporating GPs, specialists and allied health professionals can be developed to provide maximum delivery of relevant genetic data for both genetic and common multifactorial disorders.

General practice should provide comprehensive, coordinated and continuing medical care, drawing on biomedical, psychological, social and environmental understanding of health.1 The recent advances in knowledge of genetics and the human genome will inevitably require GPs to incorporate the "new genetics" into aspects of daily consultation.

Patients consult their GP for many reasons.2 At present, most genetic consultations are for single gene disorders such as thalassaemia, cystic fibrosis or haemochromatosis. This is changing fast, as genes are identified that predispose to multifactorial illnesses such as deep venous thrombosis, Alzheimer disease and some forms of cancer. The GP will have a particularly important role in interpreting these tests for patients, and then ensuring that relevant family members are offered appropriate tests in turn.

The new genetics and GP consultations
Diagnostic DNA testing

DNA testing can help diagnose the causes of many of the problems for which patients present to GPs. A common presenting problem is tiredness. In the appropriate circumstances, the GP will order tests, usually including a full blood count and iron studies. The results may lead to further investigations, including DNA tests. Haemochromatosis, a common autosomal recessive condition, is more likely to be diagnosed in the general practice setting by the early symptom of tiredness than by the textbook description of diabetes and skin pigmentation. Similarly, the finding of anaemia or microcytosis will indicate iron deficiency and/or thalassaemia. In this situation, DNA studies may be appropriate to identify an underlying thalassaemia, particularly α-thalassaemia. Factor V Leiden deficiency, or other genetic causes of thrombophilia, may be found with DNA testing after deep vein thrombosis, a condition increasingly treatable in general practice.

Except where limited by the Health Insurance Commission or health department directives, there are no restrictions on GPs ordering DNA tests. Indeed, there are important reasons why GPs should have access to DNA testing options. These include:

The testing laboratory should provide information to ensure that the significance of the test (and its limitations) are recognised. Further specialist investigation and intervention can be undertaken by referral.

It is also reasonable to expect that some GPs will refer DNA testing to specialists, because of concern about their knowledge of the new genetics,4 and the medicolegal responsibility for the consequences of the test. The GP will also carry some responsibility for ensuring that tests are offered to relatives of the index case.

Preconception counselling and prenatal DNA testing

More than 50% of women plan their pregnancy.5 A consultation before conception (eg, when a woman presents for advice on contraception) is an opportunity to explore genetic conditions that may be suitable for prenatal or pre-implantation genetic diagnosis. The family history, which the GP will often be aware of, is highly relevant in determining whether there are particular risks to the fetus, especially if the mother is older.

Prenatal testing needs to be completed by a certain gestational age, and the hospital clinic or obstetrician will not always see at-risk patients early enough for prenatal diagnosis to be undertaken in a calm and considered manner. GPs supervise an increasing number of pregnant women in shared-care programs.6 As the person of first contact, the GP is ideally placed to facilitate DNA prenatal testing by arranging for early investigation or referral to determine if prenatal testing is feasible. Various useful resources are available to guide GPs in these scenarios.7,8

Patients expect their GP to inform them in a timely manner of the existence of various prenatal testing options, from carrier testing of the couple for specific conditions, such as cystic fibrosis,9 to nuchal translucency10 in the fetus to test for Down syndrome. The new genetics increases the test options the GP needs to be aware of. For example, material collected after chorionic villus sampling in the first trimester of pregnancy can be used for a range of tests, such as fluorescent in situ hybridisation to identify specific chromosome abnormalities,11 or as a source of DNA to look for mutations in genes (eg, dystrophin to identify the risk of developing Duchenne muscular dystrophy).

Predictive or presymptomatic DNA testing

The presence of a genetic disorder in a family now allows other family members who are at risk to undertake predictive or presymptomatic DNA testing to quantify their risk or exclude the risk before clinical features of the disease become apparent.12 There are three situations GPs will face:

  • A known genetic condition exists in a family member (eg, disorders such as haemochromatosis, familial adenomatous polyposis, or Huntington disease).

  • Patients may observe family patterns of disease (eg, cancer), and request DNA testing to predict their own risk.

  • Patients may ask their GP about DNA testing options that have been raised in the media.

Conditions like familial adenomatous polyposis or haemochromatosis can be treated. Perhaps more importantly, preventive measures are possible in both. In contrast, Huntington disease is a rare and ultimately fatal neuropsychiatric disorder without any established treatment or prevention option. Therefore, the result from a predictive test in Huntington disease carries with it considerable psychological and societal implications. For optimal patient care, patients who need DNA testing for disorders requiring specialist treatment such as surgery (familial adenomatous polyposis), or rare and serious disorders requiring intensive workup and ongoing support (eg, Huntington disease), should be referred to a clinical geneticist initially. On the other hand, GPs may elect to undertake DNA tests in patients and family members at risk of common or easily treatable conditions such as haemochromatosis. These individuals can be referred for specialist treatment when needed.

Patients may exaggerate their risk of heritable cancer. The information disseminated to GPs by cancer councils13,14 is useful for providing patients with realistic risk assessments. Specific cancer genes such as BRCA1 and BRCA2 are a rare cause of breast or ovarian cancer that runs in families, accounting for 1%–2% of these cancers in the overall population. Risk assessment by pedigree allows GPs to put a patient's concern into perspective. Most patients will end up needing the same level of surveillance as the general population (eg, screening mammography). Patients with appropriate family histories benefit most from referral to the specialist cancer genetics clinics.

Challenges in integrating the new genetics into general practice

Specialist medical activity based at teaching hospitals is funded by state departments of health, and supported by university affiliations. Such activity spreads out to general practice for economic as well as medical reasons, as GP consultations are a Commonwealth cost. GPs need to participate in the new genetics, to be part of a team and to have access to suitable referral sources. They should be consulted before changes in their practice leave them undertaking work for which they may feel unskilled.

How should genetics training for GPs be delivered?

Computer tools that improve the accuracy of risk assessment, and so enhance referral patterns,15 are being developed for general practice. Suitable web-based resources are being tested in Victoria and are available to members of the Royal Australian College of General Practitioners (RACGP).2 Many GPs prefer more traditional methods of learning, which can be expensive and teacher-intensive. Watson et al compared an information pack to inhouse education for upskilling GPs on the genetic aspects of breast cancer. Both systems improved referral decisions significantly, while inhouse sessions increased doctor confidence.16

In the United Kingdom, there are initiatives such as a genetics nurse,17 who could spend three hours per month in each of 20 practices to provide GP education as well as GP and patient support. Another suggestion is a genetic counsellor,18 who could liaise with the local genetics clinic and the practice, providing genetic counselling to patients. However, the current Australian financial environment has no means to provide such initiatives with ongoing funding.

Models of care for GPs and the new genetics

In the Australian context, GPs are the entry to further medical care in all but some emergency situations. They are gatekeepers of expensive medical care, and they look after the chronic health needs of people with complex conditions.

GPs balance their own knowledge and ability to supervise a patient's medical needs, and the needs of the family, with the availability of specialists, on a background of limited resources for public care, and limited patient means for private care. To decrease the isolation of GPs undertaking the primary care of patients with complex conditions, and to accommodate the shift in care of these patients from state-based institutions to Commonwealth-funded areas of care, new models are being developed. Some are summarised below to illustrate possible approaches that would involve the GP in the new genetics.

HIV and HCV model

This model of care has been developed to acknowledge the significant increase in knowledge needed for care in this area, the continuing and changing knowledge, and the limited numbers of GPs who wish to undertake care at this level.20 If this model were applied to the new genetics, GPs would attend a training program and satisfy the relevant assessment. Training could occur in two stages: an introductory course designed for all GPs with an interest in the new genetics, and an advanced component specifically tailored to GPs who wish to expand their role and, for example, counsel in genetics clinics or in groups. The GPs would be required to designate genetics specialists with whom they would collaborate in patient management and model evaluation. To keep their status, they would be required to maintain a suitable level of continuing medical education to demonstrate their understanding of current trends. The GPs would be able to undertake community-based research in the aspects of genetics that affect their patients.

Different models of care incorporating GPs, specialists and allied health professionals can be developed to provide maximum delivery of relevant genetic data for both genetic disorders and common multifactorial disorders.

  • Linda Mann

  • 93-95 Balmain Road, Leichhardt, NSW.


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