Diagnosing CSID
In order to diagnose Congenital Sucrase-Isomaltase Deficiency (CSID), a careful review of signs, symptoms, and medical history must be performed first to determine whether a diagnostic workup for sucrase-isomaltase enzyme deficiency is warranted. The diagnostic workup can include a sucrase assay of intestinal biopsy samples, a carbon-13 sucrose breath test (13C SBT), a sucrose hydrogen-methane breath test, or an oral sucrose challenge test.
Common Signs and Symptoms
A medical history will include a review of a patient’s complaints. Patients with CSID typically present with one or more of the following symptoms:
- Chronic diarrhea and/or loose stools (acidic diarrhea, and more severe or explosive diarrhea in young children or babies after weaning)
- High bowel movement frequency
- Reports of particularly foul stool odor due to malabsorption
- Gas/bloating
- Abdominal cramps
- Complaints of nausea or dyspepsia
- Diarrhea mixed with intermittent constipation, particularly when chronically taking common antidiarrheal therapies
- Postprandial symptoms
- A low body mass index (BMI) that falls below an age-appropriate growth chart curve, or failure to thrive when very young
- Carbohydrate food avoidance or intolerance, particularly sugary sweets or starches (eg, potatoes, rice, or pasta)
- Lack of response to common antidiarrheal therapies
- Long history of diagnostic workups with multiple gastroenterologists for unusual, but similarly presenting, pathologies such as cholecystitis, celiac disease, cystic fibrosis, and bile acid malabsorption
Symptom Frequency and Duration
- Patients often report a high frequency of daily and weekly symptoms
- Symptoms typically occur after meals (postprandial)
- Symptoms have a very long-term duration, since childhood or for many years. In children, symptoms may start after weaning, with increased consumption of dietary carbohydrates in baby foods
Diagnostic Tools to Assess Sucrase Enzyme Activity
While no test on the market today is 100% accurate, and current tests, including genetic testing, cannot rule out secondary sucrase deficiency, several options are available to help assess the likelihood of a CSID diagnosis.
Test
Access
Commonwealth Labs, 1-888-258-5966
Metabolic Solutions, 1-603-598-6960