Gene sequencing expert: Test could speed diagnosis of rare diseases
Some people suffer for years from rare neurological diseases that have no known cause and, accordingly, few clear treatment choices. Those causes could become easier to diagnose – if doctors had the right tool.
Some UCLA researchers say that they already do. Using a state-of-the-art genetic test -- paired with a patient evaluation and family history -- could greatly improve the speed and accuracy with which doctors can diagnose neurogenetic disorders, they contend. Doing so, they add, could lead to better care for people with spinocerebellar ataxia, leukodsystrophy, spastic paraplegia and many other rare, often fatal, conditions.
How the test works
First, some background: Genes are DNA segments that instruct cells how to behave – but not all of the genes in a body are activated, or expressed. Whether or not a gene is expressed affects how the body performs. The new test, called exome sequencing, determines the precise order of all the expressed – or activated -- genes in a person’s genome. Assessing the order of gene expression can help researchers determine the root cause of puzzling symptoms.
Dr. Brent Fogel, first author of a review that appeared in the April issue of Neurology: Clinical Practice, points out that use of the test is currently limited due, in part, to its relative newness, complexity and expense. Using it more widely, he says, is not only doable, but worthwhile for doctors and patients alike
Arriving quickly at a proper diagnosis could end what for many patients is an agonizing, years-long journey to even find a name for their condition, let alone a treatment. And using exome sequencing is more efficient and less costly than the traditionally more common types of genetic testing, Fogel said in the review.
Who should pay?
Insurance coverage for the test has been spotty - at best. But the benefits to patients should lead to greater coverage, said Fogel, director of the Neurogenetics Clinic at UCLA and an associate professor of neurology and human genetics.
“Despite extensive literature supporting the use of this technology, many insurance companies still consider it to be investigational and may refuse coverage,” Fogel said. “Our article outlines the appropriate use, benefits and limitations of exome sequencing that these companies need to consider when making coverage decisions.”
Leader in the field
UCLA has been a leader in using clinical exome sequencing diagnostically since 2012. Fogel and his team were among the first adopters of this new technology into routine neurological practice, and he has been a strong advocate for promoting the widespread use of this technology.
This review follows a study by Fogel and colleagues published in the Journal of the American Medical Association Neurology in 2014. That study demonstrated the effective use of exome sequencing in patients with spinocerebellar ataxia, in which people lose control of the muscles in their limbs. The team demonstrated that more than 20 percent of patients could be diagnosed immediately, and that useful diagnostic information could be identified in more than 60 percent, regardless of age of onset or family history.