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How is Genetic Sucrase-Isomaltase Deficiency/Congenital Sucrase-Isomaltase Deficiency Diagnosed?

The diagnosis of Genetic Sucrase-Isomaltase Deficiency/Congenital Sucrase-Isomaltase Deficiency can be missed, especially if patients have mild, nonspecific symptoms. Correct Genetic Sucrase-Isomaltase Deficiency diagnosis may be delayed while other causes of severe, chronic diarrhea are entertained. 1

Commonly, patients are misdiagnosed with food allergy or intolerance to cow’s milk or soy protein. An improvement in symptoms while ingesting a casein-hydrosylate formula may be interpreted as support for this mistaken diagnosis, when it in fact reflects the switch from carbohydrate to glucose polymers, which are dependent on glucoamylase activity for digestion.2 Once infancy is passed and a larger variety of foods are added to the diet, it is increasingly difficult to correctly identify sucrose as the explicit cause of symptoms. In addition, there may be high co-morbidities between Genetic Sucrase-Isomaltase Deficiency and other enzymatic deficiencies involved in carbohydrate digestion.

Such co-morbidities and/or misdiagnoses may include allergic gastroenteropathy, cystic fibrosis, celiac disease, severe viral gastroenteritis, lactose intolerance, glucose-galactose intolerance or other causes of intractable diarrhea. Mild steatorrhea is commonly used to support these diagnoses. 3

As the table below indicates, there are two tests that confirm the presence of GSID. The measurement of intestinal disaccharidases (lactase, sucrase, isomaltase or palatinase, and maltase) through a small bowel biopsy is considered the gold standard for diagnosing GSID. If it is decided that the endoscopic biopsy is not appropriate for the patient, a short trial of Sucraid® (sacrosidase) Oral Solution can be given to determine if the patient responds. There are several different tests that are not diagnostic for GSID/CSID but may help in making the correct diagnosis. Some of these tests are listed in the table below.

Tests for Genetic Sucrase-Isomaltase Deficiency/Congenital Sucrase-Isomaltase Deficiency

Diagnostic Tests
Test Method
Info Regarding Test Method
Small Bowel Biopsy with Disaccharidase Enzyme Testing
  • 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
Sucraid® Therapeutic Trial
  • Sucrase enzyme replacement therapy
  • A 2-week sample of a medication called Sucraid®, which is an exogenous enzyme
Tests That Aid in Diagnosis
Test Method
Info Regarding Test Method
Sucrose Intolerance Hydrogen Breath Test
  • Noninvasive procedure
  • 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 sucrase 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
  • Must fill breath bags over a 3-hour time period after ingestion of sucrose and glucose
  • 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
Oral Sucrose Tolerance Test
  • Noninvasive procedure
  • Not specifically designed for diagnosing Genetic Sucrase-Isomaltase Deficiency
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
  • A positive genetic test supports the diagnosis of GSID. If patients are symptomatic and a negative genetic test is received, consult a physician or QOL Medical.

 What are the Treatment Options?

In patients with Genetic Sucrase-Isomaltase Deficiency/Congenital Sucrase-Isomaltase Deficiency and overt symptoms that warrant treatment, three major treatment options exist: nonpharmacologic, pharmacologic or a combination of both. Before the advent of specific pharmacologic treatment, the treatment of Genetic Sucrase-Isomaltase Deficiency consisted of lifelong adherence to a strict sucrose-free diet. However, given the sucrose content of Western diets, patient compliance with a sucrose-free diet is, at best, difficult. Patient noncompliance is common and often accompanied by continued chronic gastrointestinal symptoms, decreased weight for height and decreased weight for age. 4 5 6 In fact, in a clinical trial testing a restricted diet, 75% of patients were not asymptomatic.5

Enzyme replacement therapy with Sucraid® offers a pharmacologic alternative to sucrose-free diets. Sucraid® is an effective option for the management of sucrase deficiency that reduces or eliminates both the need for dietary restrictions of sucrose and the symptoms of Genetic Sucrase-Isomaltase Deficiency in the majority of patients. 7 In long-term clinical trials, 81% of Sucraid® patients became asymptomatic.8 Note that Sucraid® does not provide specific replacement therapy for the deficient isomaltase.9 Therefore, restricting starch in the diet may still be necessary to reduce symptoms as much as possible. The need for dietary starch restriction for patients using Sucraid® should be evaluated in each patient.

In long-term clinical trials, 81% of Sucraid® patients became asymptomatic.

Given the demonstrated efficacy of Sucraid® (sacrosidase) Oral Solution in correcting sucrase deficiency, a short therapeutic trial (e.g., two weeks) may be warranted to assess the response of a patient with suspected sucrase deficiency.9 Substantial attenuation or elimination of symptoms while the patient is on a normal, sucrose-containing diet suggests the presence of Genetic Sucrase-Isomaltase Deficiency.


  1. Ament ME, Perera DR, Esther LJ. Sucrase-isomaltase deficiency – a frequently misdiagnosed disease. J Pediatr. 1973;83:721-727.
  2. Treem WR. Congenital sucrase-isomaltase deficiency. J Pediatr Gastroenterol Nutr. 1995;21:1-14.
  3. Gudmand-Hoyer E, Krasilnikoff PA, Skovberg H. Sucrose-isomaltose malabsorption. In: Draper H, ed. Advances in nutritional research; vol 6. New York: Plenum Press, 1984:233-269.
  4. Antonowicz I, Lloyd-Still JD, Khaw KT, Shwachman H. Congenital sucrase-isomaltase deficiency. Observations over a period of 6 years. Pediatrics. 1972;49:847-853.
  5. Gudmand-Hoyer E. Sucrose malabsorption in children: a report of thirty-one Greenlanders. J Pediatr Gastroenterol Nutr. 1985;4:873-877.
  6. Kilby A, Burgess EA, Wigglesworth S, Walker-Smith JA. Sucrase-isomaltase deficiency. A follow-up report. Arch Dis Child. 1978;53:677-679.
  7. Naim HY, Roth J, Sterchi EE, et al. Sucrase-isomaltase deficiency in humans. Different mutations disrupt intracellular transport, processing, and function of an intestinal brush border enzyme. J Clin Invest. 1988;82:667-679.
  8. Treem WR, McAdams L, Stanford L, Kastoff G, Justinich C, Hyams J. Sacrosidase therapy for congenital sucrase-isomaltase deficiency. J Pediatr Gastroenterol Nutr. 1999;28:137-142.
  9. Sucraid® (sacrosidase) Oral Solution Full Prescribing Information.
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