breath testing for CSID

Breath testing for Congenital Sucrase-Isomaltase Deficiency (CSID)

Congenital Sucrase-Isomaltase Deficiency (CSID), also known as sucrose intolerance, is a rare disease in which the enzyme necessary to break down sucrose (table sugar) is low or absent. When foods containing sucrose are consumed, the sugar is not digested properly causing symptoms, such as gas, bloating, and diarrhea. The tests listed below aid in the diagnosis of CSID, but we are going to focus on the sucrose breath test:

  • Disaccharidase assay as part of endoscopy (considered the gold standard for diagnosing CSID)
  • Sucrose breath test
  • Short pharmaceutical therapy trial

Here is how the sucrose breath test works.

The breath test usually takes about three hours to complete. The day before the test, you stop eating carbohydrates for 12 hours followed by a 12-hour fast. This protocol ensures that the test is measuring only new sugar introduced into the gut instead of what was left over from earlier in the week.

After the prep, you blow into a tube or bag for your baseline breath. The next step is to introduce the carbohydrate. For CSID since we are concerned specifically about sucrose, you drink a solution of water and sugar only. Once consumed, the sugar water makes its way through the small intestine where it should be broken down and possibly into the large intestine. If the sugar makes it intact to the large intestine, the good bacteria that live there celebrate by fermenting the sugar, releasing gasses like hydrogen, methane, and carbon dioxide, as well as some water and acid.

The gasses then go through the intestinal wall and into the blood stream where they are taken to the lungs to be breathed out as waste. To measure how much of these gasses are produced, you blow into a special test tube or bag to collect the air from your lungs every 30 minutes for about three hours. If you have CSID, the amount of hydrogen or methane gas will be abnormally high, giving a positive result. However, an abnormal result is not, in itself, a diagnosis for CSID.

It is important to know that if the person taking this test actually has CSID, he or she may experience symptoms due to the large amount of sucrose ingested during the test. The breath test can be administered at home. Hopefully, this information blew you away.

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