Genetics - Recording a family history

Dr John Spicer and Dr Imran Rafi explain how to create a genetic map.

GPs and primary care team members take family histories every day in clinical practice, usually looking for patterns of polygenic disorders such as IHD, allergy, cancer or diabetes.

In doing so they are looking for evidence of increased personal risk for those disorders.

Clear illustration
The recording and interpretation of family histories is much improved by having a clear way of drawing them. Family pedigrees (similar to genograms) are the subject of this piece.

Current practice in recording of family history is limited to free text, or preferably a Read code of a family history diagnosis.

It helps to have a large sheet of paper and quite a lot of time. Computer programmes are available that record pedigrees, but they are not yet in general use and do not link with the usual GP software systems.

Geneticists use the word 'consultand' to describe the person providing the history, although that may not be the patient with the illness (proband). Standard symbols for relatives, individuals and various pathologies have been agreed by genetic authorities and these should be taken as the sole way of recording.1

Conventionally, the GP takes the history of first degree relatives initially (siblings, parents, offspring) and records these on a chart.

Learning points

1. Use the standard symbols agreed by genetic authorities when drawing a family pedigree.

2. Record the identity of the informant and the date taken.

3. The document created is always provisional.

4. Standard rules of confidentiality apply.

Males are denoted as squares and females as circles. Lines connecting individuals in families are as illustrated. The first diagram shows the family history of our hypothetical Joan Bloggs.

You will notice that some of the symbols are filled in, indicating a patient with the disorder in question. Joan and David's children are listed across the family line in birth order. Joan had two miscarriages (drawn as triangles) second and fourth in order, and a stillbirth third in order.

Their eldest and youngest children also have the disorder.

A separate list of individuals on the pedigree with a full clinical history associated is often attached to the diagram, thus leaving it uncluttered with supplementary, though important, information.

The larger diagram shows Joan Bloggs' parents represented above her sibling line and that her mother Elsie has died - denoted by the line through her symbol. Furthermore, Joan's brother Paul has the disorder as well.

The representation of family history can be extended as far as the index patient, or consultand, can recollect. Inevitably, there will be uncertainties about diagnoses, dates and other aspects of the information.

Hence, there is a need to record the identity of the informant and the date taken, as information may be changed by objective content gathered elsewhere (for example medical records).

Provisional data
Several final points should be made about the gathering of this sort of information in primary care. Although the process of drawing a pedigree is fairly straightforward, if currently unusual, the document generated is always provisional.

The individuals in the pedigree may develop new pathology after the time of the taking of the family history and it may not be updated unless the index patient informs the GP appropriately.

For this reason many practices ask their patients to tell them if close relatives develop new illnesses relevant to the family. Any pedigrees in existence can then be kept accurate.

Standard rules of confidentiality apply to family history notes or pedigree charts, and it should be remembered that both contain medical information on individuals other than the index case.

As such, the family history should be regarded as particularly confidential, before release to any third parties.

  • Dr Spicer is a GP and clinical tutor in medical ethics and law, and Dr Rafi is a GP and senior lecturer in community health sciences at St George's University of London

This topic falls under section 6 of the RCGP curriculum 'Genetics in Primary Care', www.healthcarerepublic.com/curriculum.

 

References
1. Bennet R, Steinhaus K, Uhrich S et al. Recommendations for standardized human pedigree nomenclature. The Pedigree Standardization Task Force of the Society of Genetic Counselors. Am J Hum Genet 1995; 56: 745-52.

2. Al-Gazali l, Hanan H and Al-Arrayad S. Genetic disorders in the Arab world. BMJ 2006; 333: 831-4.

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