Volume 193 - Issue 7
Family history: the neglected risk factor in disease prevention
Author: Michael J McKay
Med J Aust 2010; 193 (7): 429-430. || doi: 10.5694/j.1326-5377.2010.tb03983.x
Published online: 4 October 2010
Published online: 4 October 2010
To the Editor: I agree with Emery and colleagues1 that family history can add much to downstream clinical interventions that provide tangible benefits to the presenting patient and his or her kin. The pedigree chart has some advantages over simple narrative recording of the same details, including the ability to instantly visualise relationships between individuals and the ease with which the chart can be updated and annotated.2
There is a familial aggregation (commonly an affected first-degree relative) in up to 25% of presenting cancer patients, while around 5% will harbour a highly penetrant genetic predisposition to cancer. In the cancer clinic, an acceptably detailed family cancer pedigree can typically be obtained in even less time than the 30 minutes suggested by Emery et al.1
Steps in drawing pedigrees have been outlined elsewhere2,3 and typically involve collecting information such as simple demographics, naming and symbolising different cancer types, and recording age of onset and age of death (if relevant) for the different individuals, starting with the presenting patient. The time required to construct a three-generation pedigree would typically be around 10 minutes, making it an attractive addition to routine history taking. If a cancer pattern emerges, the pedigree should be extended as far as possible. Of course, diagnosis verification (through death registries, etc) would be required before surveillance, prophylaxis and therapy decisions are addressed in the familial cancer setting.
A convenient refresher for doctors who do not routinely draw pedigrees might be to first construct their own family tree, with reference to the symbols and relationship illustrators commonly used.2,3 It is likely that pedigrees in most clinics will be drawn by hand, at least initially, although there are software programs for pedigree creation available (eg, Family Tree Builder; <http://www.myheritage.com/family-tree-builder>).
Over the years, I have informally asked my specialist oncology trainees to routinely construct family pedigrees. I do not recall, among these highly clinically skilled doctors, one that was able to correctly draw a family pedigree until we had worked on it together. Given the benefits of family pedigree analysis across many disease categories, a little practice in pedigree drawing may be a useful exercise for many of us. Even without the requisite confirmation of disease status of the individuals represented, a simple pedigree chart, combined with quick reference to information on the potential clinical significance of any patterns it shows (eg, by consulting National Health and Medical Research Council guidelines),4 can help prioritise referrals to busy familial cancer clinics.
References
- Emery JD, Walter FM, Ravine D. Family history: the neglected risk factor in disease prevention [editorial]. Med J Aust 2010; 192: 677-678. 0_CHDDFIDI
- Johnson VP, Christianson C. Clinical genetics: a self-study guide for health care providers. http://www.kumc.edu/gec/prof/overview.html (accessed Aug 2010).
- Medicine Encyclopedia. Genetics in medicine – Part 3. Pedigree – use of pedigrees, terminology, drawing and recording pedigrees, confidentiality: social and genetic. http://medicine.jrank.org/pages/2642/Pedigree.html (accessed Jul 2010).
- Australian Cancer Network, National Health and Medical Research Council. Clinical practice guidelines. Familial aspects of cancer: a guide to clinical practice. Canberra: NHMRC, 1999. http://www.nhmrc.gov.au/publications/synopses/cp67syn.htm (accessed Jul 2010).