Biochemical genetic testing is the study of enzymes or proteins in the body that may be unusual in some way. These proteins or enzymes may work differently and lead to things such as birth defects in children. These types of problems are usually called "inborn errors of metabolism." This is because they are present at birth and affect how the body’s metabolism works. Metabolism is how the body changes food to energy and then gets rid of the waste.
There are hundreds of enzyme problems that can be studied in humans. If a problem is found with an enzyme, then DNA testing of the gene can be done. However, the approach to testing will depend on the disorder. For example, mutations in the gene that causes Tay-Sachs disease can be studied. Although DNA mutation testing is available, the current methods don’t find all possible mutations. Lab tests can be done to check for the enzymes that are lacking in people that have Tay-Sachs disease. More cases can be found using lab tests than through DNA testing alone. Biochemical genetic studies may be done from a blood or urine sample, spinal fluid, or other tissue sample.
Newborn screening is done around 24-48 hours after birth. It also involves biochemical testing for various health problems that can be caught early and treated before the child becomes sick.