Reality not hype: the new genetics in primary care 

Session I: clinical context of genetics in primary care

2. Prevalence of genetic disease

Ian Hopkinson

General Practitioner, Islington, and Senior Lecturer in Primary Care Genetic Medicine, University College London

Recent NHS policy initiatives have emphasized that genetics should be integrated into non-specialist clinical care, including general practice. This is an obvious consequence of recent developments in genetic science that indicate that most common disorders have a genetic component in their aetiology. There is a perception amongst general practitioners that genetics is concerned with the diagnosis of rare disorders that usually occur in children, and so is of limited importance to their everyday practice; however, there has been little work on the prevalence of genetic disease in general practice. We performed a notes review study to determine the prevalence of genetic disease in seven North London general practices.

Pragmatic criteria for defining patients as having a genetic disorder emerged from a study of 22 genetics experts at University College London: patients had to have a single gene disorder that was described in Online Mendelian Disorders in Man ( www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=OMIM ) or a multi-factorial disorder that affected themselves, and a minimum of two other family members.

Randomly selected sets of GPs’ notes were reviewed in practices serving ethnically and socially diverse populations. Of 1823 sets of notes, 189 genetic diagnoses were identified, revealing a prevalence of genetic disease of 10.4% . Familial cardiovascular disease, familial atopic disease, and familial psychiatric disease were the most prevalent genetic disorders.

These data indicate that a minimum of one in ten of the patients seen in primary care has a genetic disorder, in which family history may influence management of the presenting individual, and potentially of other family members. This is likely to be an underestimate, as often practitioners did not record family history data in the clinical notes, and the information that was recorded was frequently incomplete.

The identification of individuals who are potentially ‘at-risk’ of developing cardiac disease, enables close clinical monitoring of these individuals facilitating the early detection of clinical symptoms and signs. This in turn allows early treatment e.g. with lifestyle modification (diet, exercise, smoking), anti-hypertensives and/or plasma cholesterol lowering agents, all of which are effective interventions in reducing morbidity and mortality from cardiovascular disease.

Our data indicate that genetic disease is not rare in general practice, emphasizing the importance of obtaining family history data on all patients. Ongoing studies are identifying variations in a number of genes that are associated with common multifactorial disorders, which may result in the development of predictive testing for these disorders. Meanwhile family history is essential for identifying patients who require careful monitoring and early treatment.