How Does a Genetic Blood Test Diagnose Narcolepsy?


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A genetic blood test can determine whether or not a narcolepsy-associated antigen is present, reports National Institute of Neurological Disorders and Stroke. The presence of certain genetic information on chromosome six is a strong indicator of narcolepsy.

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Researchers have identified a genetic marker of narcolepsy that is present in narcoleptics of Caucasian, African-American and Japanese ethnicity. But 25 percent of people without narcolepsy also have the gene. Since the presence of the gene does not definitively diagnose narcolepsy, the absence of the gene in someone with sleep problems produces evidence that the patient does not have narcolepsy, according to Mayo Clinic.

In order to confirm the diagnosis of narcolepsy, three tests should be administered, says Mayfield Clinic. A polysomnogram measures the movement of the eyes and muscles, the electrical activity of the brain and heart, and monitors breathing during sleep. A multiple sleep latency test measures the time it takes to fall asleep. Narcoleptics fall asleep and experience rapid eye movement quickly. A hypocretin test determines the levels of the brain chemical that regulates rapid eye movement sleep by sampling the cerebrospinal fluid through a lumbar puncture. Low hypocretin levels in the cerebrospinal fluid indicate narcolepsy if no other serious condition exists, states National Institute of Neurological Disorders and Stroke.

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