Unit Code 83255:
Reducing Substance, Feces
Useful For
Diagnosing intestinal malabsorption in children
May assist in the differentiation between osmotic and nonosmotic
diarrhea
Screening test for:
- Diarrhea from disaccharidase deficiencies, eg, lactase deficiency
- Monosaccharide malabsorption
Clinical Information
Sugars (eg, glucose, galactose, fructose, maltose, sucrose,
pentose) are characterized as reducing substances based on
their ability to reduce cupric ions to cuprous ions.
Fecal reducing substances may be increased in carbohydrate
malabsorption syndromes.
Reference Values
Negative: negative
Trace: normal (<0.25 g/dL)
Grade 1: suspicious (0.25-0.50 g/dL)
Grades 2-4: abnormal (>0.50 g/dL)
Interpretation
Negative: negative
Normal: <0.25 g/dL (trace)
Suspicious: 0.25 g/dL to 0.50 g/dL (grade 1)
Abnormal: >0.50 g/dL (grade 2-4)
Cautions
A number of other compounds also are capable of reducing cupric
ions to cuprous ions and can cause false-positives.
Ambient transport temperatures result in growth of bacteria. Bacteria
consume reducing substances, which can result in false-negative
results, so ambient specimens are rejected.
This test has poor sensitivity for oligosaccharides and poor sensitivity
from diaper stools because fluid is reabsorbed into the diaper.
Testing of only the solid portion of the stool will give a falsely-low
reading since the liquid portion of the stool contains the water-soluble
sugars.
Possible interferences include: salicylates, penicillin, choral hydrate,
menthol, phenol, streptomycin, para-aminosalicylic acid, isoniazid,
ascorbic acid, cephalosporins, and probenecid.
Special Instructions and Forms
Clinical Reference
Todd S: Archives of disease in childhood: differentiation of osmotic
and secretory diarrhea by stool carbohydrate and osmolar
measurements. In Clinical Diagnosis and Management by Laboratory
Methods. Vol. 77, 20th edition. 1997, pp 201-205
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