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Thursday, July 2, 2009

Why early diagnosis of Usher syndrome is important to physicians

By Mark Dunning

We spent the last post talking about why early diagnosis is important to families, but there are other parties we need to convince about the benefits of early diagnosis as well. Families usually learn about Usher syndrome through their local physician and many physicians struggle with the diagnosis. Now realize that we're not talking about the physicians that are members of the Usher Coalition. We're talking about the typical family physician or the local specialist. These are the people that refer patients to the experts in Usher syndrome. These are the doctors that can order the genetic tests that then gets the ball rolling toward a definitive diagnosis.

Many of these doctors are hesitant to pursue a diagnosis of Usher syndrome. They want to see people improve after a diagnosis. That's the point, right? Figure out what is wrong and then fix it. But physicians worry about an Usher diagnosis. They know the emotional impact of the diagnosis on the family and those not intimately familiar with Usher know only that there is no cure. So they worry that a diagnosis of Usher syndrome might actually do more harm to a family than good.

Of course, as we discussed in the last post that is not true. A definitive Usher diagnosis is a good thing for a family for a lot of reasons. There are also additional reasons that might not be important from the perspecive of a family, but are important physicians. So that's what we'll discuss today. Let's also be clear about what we mean by a definitive diagnosis, though. We're talking about genetic testing here, molecular confirmation of an Usher mutation. We want physicians that suspect Usher to order that test. Here's why.

Eliminates Other Diagnoses
One of the best reasons for definitively diagnosing a patient with Usher is that it eliminates all other diagnosis. No physician wants to put their patient through endless tests chasing a diagnosis. Hearing loss combined with vision impairment is a common occurance. In fact, 50% of kids with hearing loss have a visual impairment of some sort versus 20% of those with normal hearing. Now, not all 50% have Usher syndrome. So chasing one of the many causes of visual impairment in kids with hearing loss can be time consuming, costly, and overly demanding of a patient. For instance, many young children require sedation to have an ERG. It's just too difficult for them to do unsedated. But a sedated ERG is hard on the child, emotionally straining on the parents, expensive, and time consuming. In the end, a physician might be able to diagnose Usher by the ERG only, but not the specific type (more on that later). A simple blood test is more definitive, more accurate, and can eliminate the excessive testing that can go along with the search for a diagnosis.

Many Upcoming Treatments are Molecularly Specific
We stated the obvious earlier when we said that physicians want to improve the lives of their patients by a diagnosis. If all goes well, we'll have treatments available to physicians in the next few years, but those treatments will most likely be molecularly specific.

One of the most promising treatments for vision loss is gene therapy. But as it says in the title, gene therapy is gene specific. A gene therapy treatment for Usher syndrome type 1b not only won't work for Usher syndrome type 2a, but it would most likely be very harmful. This is similarly true with some of the promising drug therapies. They work on specific types of mutations, such as nonsense mutations, won't work with other types and again might very well be harmful if used improperly. Remember, one of the big concerns of physicians is that there is no cure for Usher syndrome. That should change in the next few years, but it won't help any patient that has not been diagnosed molecularly.

Accurate Genetic Counseling
Genetic counseling is the process of advising families on the risks and probabilities associated with a particular inherited disorder. Families use the information for family planning and management decisions. There are a number of genetic causes of hearing loss and not only do they not have the same risks, they don't all share the same probability of occuring in future children. So accurate genetic counseling can be critical to a family and obviously it is not possible without a genetic test ordered by a physician.

So there's some physician specific reasons why early diagnosis of Usher syndrome is important. In our next post on the subject of early diagnosis, we'll talk about why funding organizations would be wise to invest in projects aiming to improve early diagnosis of Usher syndrome.

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