Tests Used During Diagnosis

Before doctors arrive at a final diagnosis of Pompe disease, they may use a variety of tests to assess different aspects of a patient’s condition. Typically, none of these tests alone can specifically identify Pompe disease. Some point generally toward a muscle disorder, while others can help detect which muscles or organs are affected.

However, the combined results can help doctors narrow down their diagnosis. Once Pompe disease is suspected, physicians can make the diagnosis with a simple blood test.[1]

Learn more about tests to confirm the diagnosis 

All the tests described below reveal some aspect or effect resulting from Pompe disease.

A conclusive way to confirm diagnosis of Pompe disease is by measuring the activity of the GAA enzyme in the blood, which is always lower than normal in people with Pompe disease.

Take Note: Ongoing Testing[2]

Most of these tests continue to be valuable even after a diagnosis of Pompe disease is confirmed. Doctors use them to assess patients’ status and monitor the disease’s progression so that the plan for care and treatment can be adjusted as needed.

Find out more about ongoing monitoring and comprehensive care 

Heart Tests[2], [3]

Tests performed on the heart are most important for infants with Pompe disease, who almost always have heart problems. Tests may include:

  • Chest x-rays to check the heart’s size (which is usually greatly enlarged in infant patients)
  • Electrocardiogram (ECG) to detect abnormal heart rhythms
  • Echocardiogram (often called an “echo”), an ultrasound that can show abnormal thickening of the heart muscle

The most seriously ill infants may require 24-hour monitoring of their heart conditions.[2]

Muscle & Movement Tests

Muscle weakness can be observed in patients’ movements and the difficulty they experience performing certain tasks. Doctors can also check muscle function quantitatively with an electromyography (EMG) test, which measures a muscle’s electrical activity.

With infants and children, it is also important to see whether they meet standard developmental milestones for their age, such as sitting up, crawling and walking,.

Breathing Tests

A variety of tests can be used to measure patients’ lung capacity, which can indicate weakened breathing muscles. In addition, sleep studies[4] — when a person is observed and tested while sleeping—can identify breathing problems that occur while lying down, which are common in Pompe disease.

Lab & Blood Tests

Testing a blood sample can identify abnormal levels of certain chemicals and substances. The most revealing one is the enzyme creatine kinase (CK), which is released into the body at unusually high levels when muscles are damaged. High CK levels are seen in most patients with Pompe disease, especially infants,[2], [5], [6] although they also occur with many other muscle disorders so they are not alone a conclusive sign.

When doctors suspect a muscle disorder, they may also take muscle biopsy, or small sample of muscle tissue. Analyzed under a microscope, the biopsy can show the buildup of glycogen inside muscle cells that causes Pompe disease. However, this can depend on the part of the body from which the biopsy was taken. Since glycogen does not accumulate in every muscle equally, it is possible to have a “clean” biopsy even if the person does actually have Pompe disease.

References

  1. Winchester B, Bali D, Bodamer O, Caillaud C, Christensen E, Cooper A, et al. Methods for a prompt and reliable laboratory diagnosis of Pompe disease: report from an international consensus meeting. Mol Genet Metab 2008;93:275-81.
  2. Kishnani PS, Steiner RD, Bali D et al. Pompe disease diagnosis and management guideline. Genet Med 2006 8:267-88.
  3. Hirschhorn, Rochelle and Arnold J. J. Reuser. Glycogen Storage Disease Type II: Acid Alpha-glucosidase (Acid Maltase) Deficiency. In: Scriver C, Beaudet A, Sly W, Valle D, editors. The Metabolic and Molecular Bases of Inherited Disease. 8th Edition. New York: McGraw-Hill, 2001. 3389-3420.
  4. Mellies U, Ragette R, Schwake C et al. Sleep-disordered breathing and respiratory failure in acid maltase deficiency. Neurology 2001 Oct 9;57(7):1290-5.
  5. Winkel LP, Hagemans ML, van Doorn PA et al. The natural course of non-classic Pompe’s disease; a review of 225 published cases. J Neurol 2006 252:875-84.
  6. Ausems MG, Lochman P, van Diggelen OP et al. A diagnostic protocol for adult-onset glycogen storage disease type II. Neurology 1999 Mar 10;52(4):851-853.

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