Creating A Medical Pedigree Getting Started

The basic medical pedigree is a graphic depiction of how family members are biologically and legally related to one another, from one generation to the next. Each family member is represented by a square (male), or a circle (female), and they are connected to each other by relationship lines. This family "map" is meaningless if the symbols cannot be interpreted from clinician to clinician. The symbols outlined here are from the 1995 recommendations of the National Society of Genetic Counselors Pedigree Standardization Task Force (Bennett et al., 1995). For personal use, you may photocopy Appendix A.1 for a handy, double-sided "cheat sheet" containing common pedigree symbols, the basic information to include on a pedigree, and a prototype imaginary pedigree using all the standardized symbols. The pedigree icons in and of themselves provide scant information; the power of a pedigree lies within the associative network of symbols.

Generally, the pedigree is taken in a face-to-face interview with the patient, before the physical examination. A patient is usually more comfortable sharing the intimate details of his or her personal and family life while fully clothed rather than wearing one of the highly fashionable rear-exposure gowns that are available in most examination rooms.

I find it useful to take a preliminary pedigree on the telephone. Many patients have limited knowledge of the health of their extended relatives. By asking medical-family history questions in advance of the appointment, the patient can do the homework of contacting the appropriate family members to get more accurate details. The patient can also help to arrange to obtain medical records (see Chapter 6). At the appointment, the pedigree that was taken by telephone can be verified with the patient. Medical-family history questionnaires can be a useful tool to collect pertinent information before the patient's appointment. However, a questionnaire should not substitute for an actual pedigree. Sample genetic family history questionnaires for cancer and a child being placed for adoption are included in Appendices A.3 and A.4, respectively.

The consultand is the individual seeking genetic counseling and/or testing . This person is identified on the pedigree by an arrow, so that he or she can be easily identified when referring to the pedigree. If more than one person (consultands) come to the appointment (for example, a parent and child, or two sisters), identify each person with an arrow on the pedigree. The consultand can be a healthy person or a person with a medical condition.

The proband is the affected individual that brings the family to medical attention (Marazita, 1995). Identifying the proband is important in genetic mapping studies and research. Some researchers use the term propositus (plural is propositi) interchangeably with proband(s). The index case is a term used in genetic research to describe the first affected person to be studied in the family. Sometimes an individual is both a proband and the consultand.

Even with the use of standardized pedigree symbols, a key or legend is essential for any pedigree. The main purpose of the key is to define the shading (or hatching) of symbols that indicate who is affected on the pedigree. The key is also used to ex-


TABLE 3.1 Essential Information to Record on Family Members in a Pedigree

Age, birth date, or year of birth

Age at death (year if known)

Cause of death

Full sibs versus half sibs

Relevant health information (e.g., height, weight)

Age at diagnosis

Affected/unaffected status (define shading of symbol in key/legend) Personally evaluated or medically documented (*)

Testing status ("E" is used for evaluation on pedigree and defined in key/legend) Pregnancies with gestational age noted LMP or EDD (estimated date of delivery) Pregnancy complications with gestational age noted (e.g., 6 wk, 34 wk): miscarriage (SAB), stillbirth (SB), pregnancy termination (TOP), ectopic (ECT) Infertility vs. no children by choice Ethnic background for each grandparent Use a "?" if family history is unknown/unavailable Consanguinity (note degree of relationship if not implicit in pedigree) Family names (if appropriate) Date pedigree taken or updated

Name of person who took pedigree, and credentials (M.D., R.N., M.S., C.G.C.) Key/legend plain any infrequently used symbols (such as adoption or artificial insemination) or uncommon abbreviations.

Table 3.1 serves as a quick reference to the information essential to record on a pedigree. Remember to document on the pedigree your name and credentials (such as R.N., M.D., M.S.), and the name of the consultand (the person who has the appointment). It is also helpful to record the name of the historian (the person giving the information). For example, a foster or adoptive parent may not have access to accurate history about the biological family of the child. Remember to date the pedigree. This is particularly important if ages rather than birth dates are recorded for family members on the pedigree. Was the pedigree taken yesterday or 10 years ago?

Use abbreviations sparingly and define them in the key. For example, CP may be short for cleft palate or cerebral palsy; MVA may mean motor vehicle accident or multiple vascular accidents; SB may be interpreted as stillbirth, spina bifida, or even shortness of breath!

Because the pedigree is part of the patient's medical record, it should be drawn with permanent ink. Using a black pen is best because blue ink may be faint if the record is microfilmed. It is acceptable to draft a pedigree in pencil; just be wary of errors in transcription. My favorite pedigree drawing tool is a correction pen that quickly obliterates my frequent drawing errors.

Draw the pedigree on your institution's medical progress notepaper (if available). A sample pedigree form is included for your use in Appendix A.2. A standardized pedigree form has the advantage that you can include common pedigree symbols as a reference on the form. This fill-in-the-blanks approach serves as a reminder to document easily overlooked family history information (such as family ethnicity and whether or not there is consanguinity). These forms are limited in that pedigrees of large families may be difficult to squeeze onto the page.

Plastic drawing templates of various-sized circles, squares, triangles, diamonds, and arrows, are helpful for keeping the pedigree symbols neat and of uniform size. Such templates are available at most art and office supply stores.

Computer software programs for drawing pedigrees are reviewed in Appendix A.5: The Genetics Library. Most of the currently available programs are not practical for drawing a quick pedigree in a clinical setting. These drawing programs are efficacious for large research pedigrees, patient registries, or in preparing a pedigree for professional publication.

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