Therefore, a negative genetic test only means that the person does not carry one of the 37 SI gene variations that are known to be associated with CSID, but they may have an SI gene variation that has not yet been identified as one that can cause CSID. While the breath tests and genetic test have not been validated to be diagnostic for CSID, they may become important tests that help in identifying patients with CSID. As with all diagnoses, a diagnosis of CSID depends on combining a doctor’s clinical findings with results from objective tests. A physical examination, medical history, and other secondary tests, such as stool pH test for acidic stool, can aid in the diagnosis of CSID.If it is clinically inappropriate or difficult to perform a biopsy or if a CSID diagnosis is in doubt, a physician may suggest a two-week therapeutic trial with an enzyme replacement. If the patient shows a reduction of symptoms it is considered diagnostic for CSID. Treatment
The two ways to manage the gastrointestinal symptoms associated with CSID are:

Diet modification that eliminates or restricts the consumption of foods containing sucrose (table sugar) or starch sugarsThe use of enzyme replacement therapy to replace the action of the sucrase enzyme that is deficient. This medication requires a prescription from a doctor.
CSID is an inherited condition characterized by a dysfunctional digestive enzyme.The purpose of the digestive enzyme, sucrase-isomaltase, is to break down the compound sugars sucrose (table sugar) and starch sugars so they will be small enough to be absorbed from the gastrointestinal tract.In addition to CSID, a primary gastrointestinal disorder such as a gastrointestinal infection, celiac disease or Crohn’s disease, can transiently suppress the digestive function of sucrase-isomaltase, causing an acquired form of sucrase-isomaltase deficiency (SID). Once the underlying disorder is treated and resolved, the symptoms of SID usually go away.A deficiency or absence of sucrase-isomaltase function is likely to cause chronic gastrointestinal symptoms whenever a person eats food containing sucrose or starch sugars, which are very common in carbohydrates. In fact, the sucrase-isomaltase enzyme is responsible for the digestion of all foods containing sucrose and approximately 60% to 80% of all foods containing starch sugars. When sucrose or starch sugars are not absorbed from the gastrointestinal tract, they travel to the large intestine (colon) where two things happen:
The food draws in excess water by a process called osmosis, creating watery diarrhea. The food is broken down by the normal bacteria that reside in the colon by a process called fermentation; byproducts of all fermentation include the production of excess gas and an acidic environment.The timing of gastrointestinal symptoms associated with CSID is distinctive. CSID symptoms are frequent, daily events; they are lifelong, and they are postprandial (occurring after eating food).