Some laboratories perform testing for other reducing substances on urine specimens from children below a certain age (eg, age 2) whenever a urinalysis is ordered. The purpose is to detect serious inborn errors of metabolism. The reducing substance assay uses the classic Benedict’s copper reduction reaction to detect glucose and other carbohydrate metabolites. If the reducing substance test is positive and the reagent dipstick assay for urinary glucose is negative, it is possible that other reducing substances are present. Further testing would be required to diagnose the exact inborn error of metabolism.
If a facility's practice is to screen all newborns for metabolic disorders, the urine test for reducing substances may be performed only when the clinician orders it, rather than the test being part of a routine urinalysis procedure. Secondary methods that test for all reducing substances are not the recommended monitoring test for diabetics; glucose reagent strip testing is a better choice.
