Diagnose Sucrose Intolerance or GSID

Diagnosis

How to diagnose Sucrose Intolerance or GSID

Diagnosing Genetic Sucrase-Isomaltase Deficiency/Congenital Sucrase-Isomaltase Deficiency in a patient can be an arduous journey. Starting with a pediatrician or primary care physician, a patient may be diagnosed with more common causes of diarrhea such as toddler’s diarrhea, Irritable Bowel Syndrome, parasites, or intestinal infections. When treatment for these conditions does not relieve symptoms, a primary care physician may decide to refer the patient to a gastroenterologist, who specializes in digestive issues.

A gastroenterologist, like the primary care physician and pediatrician, will conduct a physical examination, as well as discuss clinical, family, and diet history. Based on this information, tests may be ordered. Often with rare diseases, this process of discovery may require a systematic process of elimination of other more common ailments before an exact diagnosis can be determined.

There are different tests available to help in the determination of Genetic Sucrase-Isomaltase Deficiency, some of which are non-invasive. However, the most accurate test available is an upper gastrointestinal endoscopy with biopsy. It is considered the gold standard when it comes to diagnosing Genetic Sucrase-Isomaltase Deficiency.

In this procedure, several biopsies (tissue specimens) are obtained from the small intestine, and then sent for a specialized analysis of the enzymatic activity. The laboratory analysis that determines the sucrase-isomaltase activity is commonly known as a disaccharidase assay via a small bowel biopsy. After measuring the intestinal disaccharidases (lactase, sucrase, isomaltase or palatinase, and maltase), a definitive diagnosis for Genetic Sucrase-Isomaltase Deficiency can be identified.

Contributing factors, like the age and health of the patient, may affect the test a physician chooses to order. Your doctor may order a short treatment period with a drug known to treat this disorder. If you show improvement, you are likely to have GSID. There are two tests your doctor may order that provide useful information to help in the doctor’s diagnosis, however, they are not approved diagnostic tests for GSID.

There is a non-invasive test called the sucrose hydrogen breath test that may be ordered for a particular patient. In the human gut, only a specific type of bacteria in the large intestine is capable of producing hydrogen, so this test uses the measurement of hydrogen in the breath to diagnose gastrointestinal disorders. Bacteria produce hydrogen when the bacteria are exposed to unabsorbed food, particularly sugars and carbohydrates. Large amounts of hydrogen may be produced when there is a problem with the digestion or absorption of food in the small intestine, allowing more unabsorbed food to reach the large intestine. If there is an increase in hydrogen output while breathing, it suggests that small intestinal enzymes are not working properly. While taking the test, patients who have GSID may experience symptoms due to the large amount of sucrose consumed during the test.

In 2012, genetic testing became commercially available for Genetic Sucrase-Isomaltase Deficiency/Congenital Sucrase-Isomaltase Deficiency. Genetic testing is used to determine if a person suspected of Genetic Sucrase-Isomaltase Deficiency has any of the variants on chromosome 3 known to be associated with Genetic Sucrase-Isomaltase Deficiency/Congenital Sucrase-Isomaltase Deficiency. While this is a promising test, it has not yet been shown to be diagnostic for whether you have GSID or if your symptoms are from GSID.

Testing Methods to Aid in the Diagnosis of GSID

Test Method Info Regarding Test Method
Small Bowel Biopsy with Disaccharidase Enzyme Testing
  • The gold standard (definitive) for diagnosing sucrase deficiency
  • Requires an invasive procedure called an upper endoscopy or EGD
  • Sample requires rapid freezing and transfer to a specialized laboratory
Sucrose Hydrogen Breath Test
  • Extensively validated, but not specific for diagnosing Genetic Sucrase-Isomaltase Deficiency
  • Requires a special diet 24 hours before test and 12 hours of fasting
  • Must catch breath into 6 tubes over a 3-hour time period after ingesting a sucrose solution
  • Patients with Genetic Sucrase-Isomaltase Deficiency may experience symptoms due to the large consumption of sucrose
13C Sucrose Breath Test
  • Noninvasive
  • Newer procedure
  • Requires fasting for at least 3 hours
  • Mass spectrometry
  • Specific test for Genetic Sucrase-Isomaltase Deficiency
  • Does not produce symptoms in Genetic Sucrase-Isomaltase Deficiency patients because it does not require excessive consumption of sucrose
Stool pH Test
  • An indirect test for carbohydrate malabsorption
  • Not specific for sucrose malabsorption
4-4-4 Simple Oral Sugar Challenge
  • The test is short, simple and can be performed in the privacy of the patient’s home
  • Step 1: Stir 4 tablespoons of ordinary table sugar into a 4-ounce glass of water. Mix until sugar is completely dissolved
  • Step 2: Drink it on an empty stomach
  • Step 3: See if symptoms such as bloating, gas, and diarrhea occur during the next 4-8 hours; this suggests sucrose intolerance is possible
SI Genetic Test
  • Noninvasive procedure
  • Analysis of sucrase-isomaltase exon for the presence of one of 37 known pathogenic polymorphisms
  • Genetic sample collected via buccal swab on the inside of cheek
  • Positive genetic test supports the diagnosis of GSID
  • If a patient is symptomatic and a negative genetic test result is received, consult a physician