Stool reducing substances test

A stool reducing substances test is done if the doctor suspects you have diarrhoea and its associated symptoms such as abdominal pain or bloating caused by any of the following conditions:

• Deficiency of the enzyme disaccharidase: Disaccharidase breaks down disaccharide sugar molecules for assimilation in the intestine. Deficiency of this enzyme will lead to carbohydrate accumulation in the gut, ultimately leading to diarrhoea, abdominal pain and dyspepsia.
• Abnormalities in the absorption of carbohydrates caused by conditions such as coeliac disease, sprue or viral gastroenteritis.
• Short bowel syndrome: It is a group of symptoms related to poor absorption of vitamins, minerals and nutrients in the small intestine. Short bowel syndrome is characterised by loose, watery stools. It mainly occurs after surgeries that involve removal of a portion of small intestine for the treatment of birth defects, injuries or intestinal diseases.
• Necrotising enterocolitis: Necrotising enterocolitis is a progressive, life-threatening condition affecting mostly newborns. It occurs due to infections or injuries of intestinal tissues which then get damaged and die. Symptoms of the condition include fatigue, diarrhoea, decreased appetite and increasing abdominal girth.
• Lactase deficiency: Lactase is an enzyme that is responsible for breaking down the sugar lactose in body. People who are deficient in lactase are unable to digest lactose. Lactase deficiency is usually the cause of lactose intolerance, though lactose intolerance may also occur due to other causes. Individuals with lactase deficiency may develop bloating, pain, flatulence and diarrhoea after consuming lactose-containing food. (Read more: Lactose intolerance symptoms)

This test is useful in distinguish between diarrhoea caused by viral infections or parasite infection and diarrhoea caused by abnormal excretion of various sugars.

Certain drugs such as salicylates, neomycin, kanamycin, streptomycin, methotrexate, cephalosporins, penicillin or ascorbic acid can lead to false-positive test results or interfere with the test; therefore, you should inform the doctor if you are taking any such medicines.

You will be provided with a plastic container to collect a stool sample. The sample must be sent to the laboratory within four hours or else bacterial fermentation may occur and lead to false results. If for some reason, you can’t submit the sample within the time limit, you can keep it in the refrigerator for a while. As the liquid part of the stool is important for the test, do not collect the sample from a disposable diaper, which absorbs the liquid part of the stools.

Normal results:

• <0.25 grams per decilitre (g/dL) or <13.9 millimoles per litre (mmol/L) of reducing substances present in the stool indicate a normal result.

Abnormal results:

• 0.25-0.50 g/dL or 13.9-27.8 mmol/L of reducing substances present in the stool may point to an abnormality in the intestinal absorption of sugar.
• >0.50 g/dL or >2.78 mmol/L of reducing substances present in the stool signifies an abnormal result.

High levels of reducing substances in the stool suggest the presence of conditions such as lactase deficiency, lactose intolerance, conditions associated with carbohydrate malabsorption, short bowel syndrome, disaccharidase deficiency, necrotising enterocolitis. 

Increased levels of reducing substances in stools may also be found in newborns.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.