What Do Blood Test Results Mean in Fabry Disease?

What Do Blood Test Results Mean in Fabry Disease?
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There are various blood tests that doctors can use to diagnose Fabry disease, a progressive genetic disorder caused by a mutation in the GLA gene. It can be confusing for patients and their families to understand what doctors are looking for and what the test results might mean. Here’s some information that should help.

Enzyme assay

Initially, a combination of signs and symptoms may lead your physician to suspect you have Fabry disease. He may ask you to undergo testing to confirm or disprove his suspicion.

The main blood test your doctor will order is an enzyme assay. It assesses the amount of alpha-galactosidase enzyme activity in your blood. This is the enzyme that is defective in Fabry disease patients. A dried blood spot is sufficient for this test.

Depending on the activity of the enzyme, doctors may diagnose patients with either classic (type 1) or non-classic or late-onset (type 2) Fabry disease. Those with classic Fabry disease typically have enzyme activity below 1%. In people with late-onset Fabry disease, enzyme activity is usually more than 1%.

While doctors also can use this test in female patients, a genetic test is more reliable, particularly if there is no family history of the disease. In fact, such testing is necessary to confirm the presence of the disease in women. This is because Fabry disease is a so-called X-linked disease, when the disease-causing mutation is in a gene located on the X chromosome. Because females have two X chromosomes, they usually have milder symptoms even if they have one X chromosome carrying a faulty gene.

Lyso-Gb3 test

Doctors can use another blood test to gauge the disease’s severity. In Fabry disease, the alpha-galactosidase enzyme functioning improperly leads to the accumulation of a fatty substance called globotriaosylceramide (Gb3). This test looks at the levels of Gb3 in the blood. High levels of Gb3 can efficiently identify both classic and late-onset Fabry disease.

Clinicians can measure the levels of Gb3 using a technique called electrospray ionization liquid chromatography-mass spectrometry. However, not all laboratories provide this niche diagnostic test.

In a study of 38 patients diagnosed with Fabry disease, scientists used the spectrometry assay to determine Gb3 levels in the blood. They determined that a cut-off value of 0.81 ng/mL (nanograms per milliliter) was able to separate patients with Fabry disease from healthy individuals.

Genetic test

Clinicians also can use blood samples for genetic testing. This test seeks out mutations in the GLA gene that are known to cause Fabry disease and may help confirm a diagnosis. There are more than 965 such mutations that doctors know to cause Fabry disease. Mutations in the GLA gene are identified by a complete sequence analysis of the gene.

The most common type of mutation changes a single protein building block — amino acid — in alpha-galactosidase A. Mutations that completely eliminate the activity of the enzyme lead to the severe, classic disease, which typically begins in childhood. Mutations that lower, but do not completely eliminate, the enzyme’s activity usually cause milder, late-onset Fabry disease.

 

Last updated: Aug. 21, 2020

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Fabry Disease News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website

Mary M. Chapman began her professional career at United Press International, running both print and broadcast desks. She then became a Michigan correspondent for what is now Bloomberg BNA, where she mainly covered the automotive industry plus legal, tax and regulatory issues. A member of the Automotive Press Association and one of a relatively small number of women on the car beat, Chapman has discussed the automotive industry multiple times of National Public Radio, and in 2014 was selected as an honorary judge at the prestigious Cobble Beach Concours d’Elegance. She has written for numerous national outlets including Time, People, Al-Jazeera America, Fortune, Daily Beast, MSN.com, Newsweek, The Detroit News and Detroit Free Press. The winner of the Society of Professional Journalists award for outstanding reporting, Chapman has had dozens of articles in The New York Times, including two on the coveted front page. She has completed a manuscript about centenarian car enthusiast Margaret Dunning, titled “Belle of the Concours.”
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Özge has a MSc. in Molecular Genetics from the University of Leicester and a PhD in Developmental Biology from Queen Mary University of London. She worked as a Post-doctoral Research Associate at the University of Leicester for six years in the field of Behavioural Neurology before moving into science communication. She worked as the Research Communication Officer at a London based charity for almost two years.
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Mary M. Chapman began her professional career at United Press International, running both print and broadcast desks. She then became a Michigan correspondent for what is now Bloomberg BNA, where she mainly covered the automotive industry plus legal, tax and regulatory issues. A member of the Automotive Press Association and one of a relatively small number of women on the car beat, Chapman has discussed the automotive industry multiple times of National Public Radio, and in 2014 was selected as an honorary judge at the prestigious Cobble Beach Concours d’Elegance. She has written for numerous national outlets including Time, People, Al-Jazeera America, Fortune, Daily Beast, MSN.com, Newsweek, The Detroit News and Detroit Free Press. The winner of the Society of Professional Journalists award for outstanding reporting, Chapman has had dozens of articles in The New York Times, including two on the coveted front page. She has completed a manuscript about centenarian car enthusiast Margaret Dunning, titled “Belle of the Concours.”
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