What is genetic risk assessment?
In a genetic risk assessment, a genetic counselor, an MD medical geneticist, or Ph.D. clinical geneticist examines the patient's personal and family medical history to discover if the individual has an increased risk for developing a genetic disease or having children with birth defects or genetic disorders. Most initial visits for a genetics consultation include collecting a history with a detailed family tree. An MD geneticist may also perform a physical examination. During the genetic counseling appointment, specific laboratory tests may be suggested or recommended to obtain additional diagnostic information in order to improve the accuracy of risk estimates.
What kinds of health concerns should be brought to a geneticist or genetic counselor?
A geneticist or genetic counselor is a health care provider who assists patients at different stages of life with a variety of health concerns about diseases that may run in families. For adults, questions often center on disorders such as cancer, diabetes, or dementia. Much of the time, when several members of the same family blood line have similar diagnoses (with the same disease or related disorders), a common question is whether or not the problem is inherited. Genetics health care is the best way to find out if the problem that seems to run in your family is caused by genetic inheritance or by random chance. Once you know what your risks are, you may be able to modify your lifestyle or intervene in other ways to minimize the risk that you will actually become ill.
Do all geneticists or genetic counselors see patients for all genetic questions?
Many geneticists and genetic counselors have specialized in only one group of health concerns. For example, genetic clinics that offer services for familial cancers only see patients for this group of problems, and would be a good choice whether the family members have breast, colon, ovarian, or other cancers. However, these clinics are not likely to serve patients seeking assistance for questions regarding pregnancy and birth defects. Similarly, genetic counselors who specialize in serving prenatal patients are unlikely to see patients for adult-onset disorders such as Alzheimer's or Parkinson's diseases, and familial colon or breast cancers. Since geneticists may have trained in pediatrics, obstetrics and gynecology, internal medicine, family practice, neurology, or even dentistry, ophthalmology or dermatology, an individual genetics practice may be limited to disorders that overlap the physician's initial field of training and specialization.
What are the different types of genetic tests that may be recommended?
During a genetics appointment, several different types of tests may be recommended. Here is a short list of the general categories of genetic tests:
- Chromosome analysis
- Mutation screening
- Gene sequencing and more complex molecular tests, including next generation sequencing and whole genome sequencing
- Microarray tests, sometimes called comparative genomic hybridization or CGH testing, or "oligo-SNP" array tests
- FISH and molecular cytogenetic tests
- Biochemical genetic tests (amino acid assays, organic acid assays, acylcarnitine profiles, enzyme tests, homocysteine or methylmalonic acid levels)
- Imaging tests (X-rays, ultrasound, MR or CT scans; molecular imaging with PET or SPECT scans)
- More routine tests that can screen for genetic disorders (complete blood count, maternal serum screens, etc.)
What is prenatal screening?
When a woman is pregnant, she may naturally have concerns about the health of her unborn child. Sometimes she may feel concerned because she herself has a medical disorder, such as diabetes mellitus or systemic lupus erythematosus, which places her pregnancy at risk. Other times she may be concerned because she has already had multiple miscarriages, or because her family has a history of relatives with birth defects, or simply because she will be age 35 years or older at the birth of her child. Any of these problems may suggest to the primary care physician, obstetrician, or midwife to recommend prenatal diagnosis and genetic counseling. The healthcare provider may screen each patient by asking a series of questions examining the possibility of increased risk or may ask the patient to fill out a questionnaire such as the GeneScene Screen for Birth Defects. The patient may also be screened through blood or other tests before or during the pregnancy.
One common type of prenatal screening is the maternal serum screen. This testing can be done during the first trimester of pregnancy, during the second trimester of pregnancy, or by using testing done during both the first and second trimesters of pregnancy. When results from both the first and second trimesters are combined to arrive at a single risk assessment, the test is called an integrated screen. Often, ultrasound measurement of the back of the fetal neck is combined with results of serum testing to give the risk assessment with the highest accuracy.
What is prenatal diagnosis?
Prenatal diagnosis includes screening studies such as the maternal serum quadruple marker test, the maternal serum integrated screen, or carrier testing for any indicated genetic diseases. Another frequently recommended test is an ultrasound examination of the growing fetus. Ultrasound examination may be suggested more than once during a pregnancy. More invasive but more conclusive studies include amniocentesis or chorionic villus sampling. If a severe problem is suggested, a percutaneous umbilical blood sample may be offered. A genetic counselor or medical geneticist may be asked to discuss with the patient her genetic risks, each of these studies, the risks and benefits of these tests, and reasons why specific tests may be recommended. Prenatal diagnosis may reassure a woman that her pregnancy is progressing normally or it may be used to help better prepare a family for a more unfortunate outcome to a pregnancy.