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Biochemical enzymatic tests
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These tests are used to diagnose diseases in which the exact enzyme deficiency is
known and its activity can be tested (e.g.
Tay Sachs disease, Gaucher's
disease).
The tests are performed on the tissue in which the protein is expressed. In several
biochemical abnormalities the enzyme is not expressed (i.e. not functioning) in
the blood - therefore to demonstrate the deficiency of the enzyme by performing
a blood test would not be relevant. In these cases, the biochemical test should
be performed on the affected tissue, such as brain (in diseases affecting the brain),
muscle tissue (in the muscular dystrophies), liver biopsy (in diseases where abnormal
metabolites are stored in the liver), or other tissues according to the type of
disease. For diseases where the action of the enzyme is manifested in the skin,
amniotic fluid and
chorionic villus sampling are appropriate.
Usually, these tests are performed when there is a family history with a concomitant
high risk of recurrence of the disease. They are also performed when it is known
(through DNA screening) that one of the partners carries defective genes that can
be detected using enzymatic methods (checking the enzyme level).
(See amniocentesis
- other amniotic fluid tests that can be performed)
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