How to diagnose Sucrose Intolerance or GSID
Diagnosing Genetic Sucrase-Isomaltase Deficiency (GSID)/Congenital Sucrase-Isomaltase Deficiency (CSID) in a patient can be an arduous journey. Starting with a pediatrician or primary care physician, a patient may be misdiagnosed with more common causes of diarrhea such as toddler’s diarrhea, Irritable Bowel Syndrome, or intestinal parasites or 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 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 a GSID diagnosis is investigated.
There are different tests available to help in the determination of GSID, some of which are non-invasive. However, the most definitive test available is an upper gastrointestinal endoscopy with a small bowel biopsy. 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. Measuring the intestinal disaccharidases (lactase, sucrase, isomaltase or palatinase, and maltase) helps inform a diagnosis of GSID.
There is also a non-invasive test called the sucrose hydrogen breath test that may be ordered by your physician. Large amounts of hydrogen may be produced by normal, natural bacteria in your large intestine when there is a problem with the digestion of sugar, which occurs in the small intestine when sucrase-isomaltase is functioning normally. If sucrase-isomaltase is not functioning normally, then there is often an increase in hydrogen output in your breath after drinking a drink with sugar. While taking the test, patients who have GSID may experience symptoms due to the large amount of sucrose consumed during the test.
Diagnostic tests are not perfect, and some of the most important factors in diagnosing GSID are the signs and symptoms. It is very important to let your doctor know about specific signs and symptoms of GSID including: chronic and frequent (several times a week), long-term diarrhea, gas, bloating and abdominal pain, (often since childhood), symptoms that occur after eating, and symptoms that are related to sugary/sweet foods like cake, cookies and ice cream (or avoiding these foods because they have given you symptoms in the past). Your doctor may order a short treatment period with a drug known to treat this disorder. If you show improvement, you may have GSID.
Testing methods to aid in the diagnosis of GSID
|Test Method||Info Regarding Test Method|
|Sucrase Disaccharidase Assay||
|Sucrose Hydrogen Breath Test||
|4-4-4 Simple Oral Sugar Challenge||