Paternity and parentage testing

Description
Parentage or identity testing is genetic testing that's done to determine if a biological relationship exists between two people. When determining the biological father of a child, the procedure is often referred to as paternity testing. Deoxyribonucleic acid (DNA) analysis and other genetic tests are used to compare the genetic material and gene markers of the child with those of each parent. When the man being tested does not have similar genetic characteristics to the child, he is excluded as a possible father. If he and the child are found to have similar genetic characteristics, the probability of him fathering the child is determined. With current testing methods, it's possible for the father to be determined with 99 percent accuracy or better. This level of accuracy is legally acceptable in a court of law. Family studies can be done in a similar manner to determine other family relationships, such as with an alleged mother, sibling or grandparent.

Understanding DNA
Deoxyribonucleic acid is a substance found in the center of cells and carries hereditary information. DNA is found in nearly every cell in the body, including the blood, skin, bones and buccal mucosa (found on the inside of the cheek). Each child inherits half of his or her DNA from the biological mother and half from the biological father. Unless you have an identical twin (who would share your DNA), your DNA is unique to you. It remains the same throughout your life.

Purpose/indications
Paternity testing is done when the identity of a child's father is in question or dispute. Family studies may be done for many reasons, such as establishing the relationship between a mother and child or siblings who were separated at birth, or determining if twins are identical.

Patient preparation
Before having your blood drawn or submitting other fluid or tissue samples, you may be required to show a photo ID and/or be fingerprinted to document your identity. Although fasting before a blood test is usually not necessary, it's a good idea to check with your lab for any specific instructions. If you'll be having chorionic villus or amniotic fluid sampling, discuss preparation with your doctor.

Procedure
For paternity testing, samples of certain body fluids or tissues are taken from the mother, child and alleged father. Typically, the child's DNA is first compared to the DNA of the mother. Half of the child's DNA will match the mother's DNA. Any DNA characteristics found in the child but not in the mother must be inherited from the father. This remaining DNA is then compared to the DNA of the alleged father.
The most commonly used samples are blood and buccal mucosa, but semen, hair or other tissues may also be used. If testing is done while the mother is pregnant, a chorionic villus sampling or amniocentesis can be used for tissue sampling. If testing is done at birth, the placenta or umbilical cord blood can be used.

Test results are typically available in about three weeks. Testing is still possible when the mother is unavailable, but it requires additional testing time and often higher fees. Family studies are done in a similar manner, but may be more complicated.


Benefits
Paternity testing can help foster emotional, social and economic support of the child. The information may help you make important decisions regarding marriage, divorce or separation. When the father is identified, accurate medical histories will also be available to the child.

Risks
Prenatal paternity tests through chorionic villus sampling or amniocentesis both involve a risk of miscarriage. Also, an emotional conflict among everyone involved, including the child, is likely when another man is identified as the father after the man who thought he was the father has bonded with the child and offered his emotional and financial support.

Postprocedure care
No special care is necessary after routine DNA analysis. If you've had chorionic villus sampling or amniocentesis, discuss postprocedure care with your doctor.

Considerations
The cost of paternity testing is usually not covered by insurance. Depending on the type of testing, it may be expensive.

Certain limits may exist for newborn testing because of the transfer of proteins from the mother to the baby.

Interpreting test results can be complicated for people who've recently had bone marrow transplants or blood transfusions.

The American Association of Blood Banks has established an accreditation program for laboratories conducting paternity tests. Make sure the lab you choose is accredited by this organization.

Testing facilities may offer expert witness services at additional cost if the test results must be submitted in court.