Measurement of reducing substances may occasionally be useful in investigation of paediatric patients with suspected malabsorptive conditions. This testing is not routinely performed and will only be requested by a specialist in paediatric gastroenterology.
The presence of sugar in the urine (mellituria) may be the result of either physiological or pathological conditions affecting absorption, metabolism or renal function. Detection of sugar in faeces is due to malabsorption; this can be due to a number of reasons such as diarrhoea or disaccharide intolerance. In faeces a negative result does not exclude sugar malabsorption as the normal gut bacteria may metabolise any sugars present especially if the sample is stored for prolonged periods. Similarly, old urine samples may give a falsely negative result. Although glucose is the commonest reducing substance detected it is not the only sugar that will give a positive screening result. There are several other reducing substances that will also give a positive reaction.
Generally not detectable in health; qualitative report provided by the reference laboratory.
Stool (5g) or urine (2mL) specimen in a plain container (blue top stool collection or white top plain universal are both acceptable). Specimen must be transported to the laboratory as soon as possible to enable it to promptly frozen (specimens are transported to referral laboratory frozen on dry ice).
Biochemistry department, Alder Hey Children’s NHS Foundation Trust, Liverpool