Diagnosing Usher, genetic testing and counselling
Diagnosis of Usher syndrome
Usher syndrome is commonly diagnosed via clinical assessments of hearing, vision, and in some cases, balance. These tests are also used to manage and assess the progression of Usher syndrome; they are as follows:
- Ophthalmology- tests such as the visual acuity test, slit lamp biomicroscopy, visual field test (Goldmann Perimetry), fundus photography, optical coherence tomography (OCT) and electroretinography (ERG) may be used for monitoring a patient’s vision.
- Audiology- tests such as pure tone audiometry (PTA), tympanometry, stapedial reflex measurement and transient evoked otoacoustic emission recordings may be used to monitor a patient’s hearing.
- Balance- tests such as the infrared video nystagmography (VNG) and the rotary chair system may be used to monitor a patient’s balance.
A brief description of the clinical assessments used to assess vision, hearing and balance can be found in ‘Clinical Assessments for Vision, Hearing and Balance’ [Sense, 2014].
Genetic testing of Usher syndrome
Genetic testing can also be used to make, or confirm, a diagnosis of Usher syndrome.
What is a genetic test?
A genetic test is when an individual is checked to see if they are carrying a specific mutation in one of their genes and whether they are at risk of developing or passing on a particular genetic condition. For someone with a diagnosis of Usher, who is the first person to be tested in the family, neither the gene nor mutation will be known. In that case, the genetic test will look at many different genes to determine the one causing the condition.
A genetic test usually requires a blood sample to be taken from the individual. Equipment and techniques are then used to extract the DNA from the blood sample so the genetic information can be scanned. The individual’s DNA can then be screened for the specific mutation in question.
Genetic counselling differs from genetic testing. It is the process by which affected individuals, and in most cases their families, are given information, by a specially trained professional (either a genetic counsellor or a clinical geneticist), on their genetic condition. Topics include the nature of the condition, inheritance pattern and the implications of their condition. Genetic counselling is designed to enable individuals to make informed medical and personal decisions or simply provide answers for any questions they may have.
Importantly, genetic counselling will enable individuals to understand the impact genetic testing may have on their family, their employment and their insurance prior to taking the genetic test.
Genetic counselling is not the same as counselling therapy used for treating certain conditions such as depression and anxiety.
How to get genetic testing and genetic counselling
If you would like to have genetic testing you should speak to your GP to request a referral to a genetic clinic. Any results from a genetic test may then prompt your GP to recommend a referral for genetic counseling. Otherwise you should ask them to refer you yourself. You may need to explain why either genetic testing or counseling would be useful to you.
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Created: February 2016
Review due: February 2018
First published: Wednesday 2 December 2015
Updated: Monday 16 January 2017