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Non-laboratory evaluation

Non-laboratory evaluation includes a detailed family history and clinical assessments of the signs and symptoms of HD. The number and types of tests carried out will vary depending on the organisation and progression of disease. These tests are only useful in patients exhibiting symptoms of HD.

Tests to assess motor, cognitive and behavioural patterns.
    A collection of simple, clinical tests performed by doctors or nurses to determine
    the presence and severity of motor, cognitive and behavioural symptoms.

MRI or CT scans.
    Provides an image of the brain showing areas of degeneration. Imaging tests are not very useful
    in early stage HD because they are unable to show small regions of neural deterioration.

Laboratory testing

Molecular genetics testing

Molecular genetics testing is used to determine if the patient has an allele, or gene variant, that predisposes to Huntington’s disease. It can be used to confirm a clinical diagnosis of HD and for predictive testing in asymptomatic patients. The most common approach used is direct mutation analysis which involves analysis of the patients DNA to estimate the length of the CAG repeat mutation. There are a number of different methodologies adopted of which the most widely used are based on PCR (polymerase chain reaction) and for large CAG expansion either Southern blots analysis or Triplet-repeat primed PCR (TP PCR) is used

Predictive testing

Routine screening of the general population is not recommended, especially due to the lack of effective intervention to stop the onset of disease. However, it should be considered in individuals at an increased risk of HD, that is, in those with a family history of HD. This is done using molecular genetic testing as described above. Predictive (presymptomatic) testing, is offerd to individuals in affected families who are at a 50-25% risk of developing HD. Testing during pregnancy can be done to determine if a fetus is affected (prenatal testing) via an amniocentesis or chorionic villus sample. Preimplantation genetic diagnosis (PGD) may be a valuable option for couples who wish to avoid transmitting the disease without revealing their own status and to avoid termination of a pregnancy.

Last Review Date: March 1, 2018