The test is performed on the patients themselves – even if there is only one. These
tests involve examining the soundness of the gene products, i.e. the proteins, without
examining the sequence of bases, so that the mutation itself is not demonstrated.
The result can establish the existence of the disease being investigated.
This is a short, simple and more rapid test than establishing the entire gene sequence.
However, it cannot always serve as a prenatal diagnostic tool. It is advisable to
test for the exact defect afterwards.
If the defect is found using this method, it is possible to identify who else in
the family carries the same mutation and who is therefore considered to be affected.
The fetus can also be tested for the defect when one of the parents is affected,
allowing for prenatal diagnosis.
If a patient cannot be examined:
It is impractical (but possible) to check family members (or the fetus) directly
using the same methods, which are time-consuming and complex.