Genetic testing sheds light on degenerative eye disesase

Now, here's a genetic test I would be very interested in and would be willing to pay for. My mother and her sister both have lost much of their eyesight to macular degeneration. I thought there was just "wet" and "dry" macular degneration and, frankly, have been avoiding the issue because I greatly fear blindness.

I learned today in an article in Science Daily (http://www.sciencedaily.com/releases/2007/02/070213173952.htm) that at least four genes identified for varieties of macular degeneration and genetic tests already exist. Also, treatments are being approved now that might be helpful to me. I already have my eye exams yearly, including a retinal examination. And I know that treatments are being tested and approved. Now, it may be time for me to decide whether to have genetic testing and, if so, where to have it done.

I've told you readers many times to look at how you will deal with the results before you choose to have genetic testing, and the authors of today's article in Science Daily--whose title I stole for the title of this blog entry--apparently seem to agree. I'm writing today about that article, rather than the University of Michigan Health System news release, or the original article in the Archives of Ophthalmology because I feel that the public is more likely to see common newspapers or online sources than professional journals or university notices.

The article quotes Dr Radha Ayyagari as urging people to prepare for all possible results:

Genetic counseling is a crucial part of the genetic testing process, particularly when the patient may face the possibility of blindness, says Ayyagari. The family needs to prepare for all possible test results, understand the implications of test results for the patient and other family members, and be aware of the limitations of genetic testing. If physicians do not have the time or skills to provide this background, Ayyagari urges them to refer their patients to genetic counselors.

So, here's some of the news I read in the article:

Ayyagari and her colleagues report on 350 genetic tests conducted since 1999, when the U-M Ophthalmic Molecular Diagnostic Laboratory became one of the first laboratories in the nation to receive government approval for ophthalmic testing under the Clinical Laboratory Improvement Amendment (CLIA). For each test described in the current study, scientists analyzed one or more of eight genes known to cause diseases of the retina.

Here's the response to one of my first criteria for submitting to genetic testing: the laboratory doing the test has to be CLIA certified. Although there is no specific certification yet for genetic diseases, a laboratory meeting CLIA standards for biologic testing is more likely to be qualified to perform the tests in which I would be interested than a laboratory not CLIA certified.

Costs and how to get the test done?

The U-M Kellogg Eye Center's Ophthalmic Molecular Diagnostic Laboratory was established by Paul A. Sieving, M.D., Ph.D., formerly a U-M faculty member and now director of the National Eye Institute. For further information on the laboratory, see the web site at http://www.kellogg.umich.edu/research/eyegenetest.

I checked the site and found the contact information I needed.

What do the tests test? The necessary info is available on the website. Plus, there's a lot of information directed to the interested person:

Please let us know if you are interested in a gene that is not on this list.

Indications for molecular diagnostic testing

  • Clinical diagnosis for patients with signs and symptoms of disease.
  • Pre-symptomatic testing for individuals who do not have the disease but, given family history, are at risk for the disease.
  • Carrier testing for individuals who may carry a gene mutation that can be passed on to children.

Comprehensive services include:

  • Certified laboratory testing (CLIA ID# 23D0964501)
  • Written report of results for the patient
  • On-site genetic counseling for patients both before and after testing. The pre-test session educates patients about the scope of testing and helps them set realistic expectations; the post-test session will help patients interpret results and their implications for the patient and family members.

The Ophthalmic Molecular Diagnostic laboratory accepts referrals from:

  • Ophthalmologists, genetic counselors, geneticists and other health care professionals
  • Patients with a designated health care provider to receive the report and discuss the results with them

For additional information, contact
phone 734-647-6347
fax 734-936-7231
eyegenetest@med.umich.edu

How good are the tests? I can check the peer-reviewed professional publication, the credibility of the journal in which the article was published, and previous publications and determine for myself whether the news article is accurate in saying:

Ayyagari and her colleagues report on 350 genetic tests conducted since 1999. For each test described in the current study, scientists analyzed one or more of eight genes known to cause diseases of the retina.

Of the 350 tests, 266 were performed to confirm a clinician's diagnosis, by far the most common use of genetic testing for eye disease. Another 75 tests sought to determine whether an individual was a "carrier" of a disease, and nine tests were used to predict the likelihood that an individual with a family history of a given eye disease would go on to develop it.

Ayyagari's team was able to determine the molecular basis of the disease in half of 266 tests conducted to confirm a diagnosis. The study also reported that a diagnosis could not be confirmed in 133 cases, or half the tests conducted to confirm a diagnosis.

And, I can read what the scientists say about the purpose of the testing and how the testing is used:

The authors observe that genetic testing for eye disease is a relatively new and evolving practice. Says Ayyagari, "Molecular diagnostics does not replace the necessary expertise of the ophthalmologist; rather, it adds a new tool to the ophthalmologist's diagnostic arsenal."

These results are significant because many retinal diseases present similar symptoms, and it is sometimes difficult for even the most skilled specialist to distinguish one from the other. By comparing a patient's DNA to known disease-causing genes, scientists deliver information needed to confirm or rule out a diagnosis. To date, scientists have identified over 130 genes associated with retinal disease, such as retinitis pigmentosa and macular degeneration.

What about all those negatives?

"It is very difficult for patients to understand that the test may not be definitive," says Ayyagari. "Genetic testing may not always yield the firm facts we receive in other kinds of testing, such as blood tests for cholesterol levels."

I have a lot of what I need from the Science Daily article, which I consider a reputable source of information, and can access a lot more with some more time at the computer and in the library.

Now, all I have to deal with is what I started with: what will I do with the results? I will not do the testing until I can answer that question.

If you have had genetic testing, what steps did you go through deciding what to do? Perhaps you ordered a test for the fun of it, were encouraged by a friend, or wanted to learn something without your insurance company knowing. Go to the "Your Stories" link at the top of the page, and send us your story. You will have to supply your name and e-mail addres, but neither will be printed or shared with organizations beyond Geneforum.

Marie Godfrey, PhD

 

 

 

 

 

 

 

 

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