A urinalysis shows positive reducing sugars while the glucose dipstick is negative. What is the most likely interpretation?

A urinalysis shows positive reducing sugars while the glucose dipstick is negative. What is the most likely interpretation?

• A. This is commonly observed with ascorbic acid interference.
• B. This may suggest a deficiency in galactose-1-phosphate uridyl transferase.
• C. This may suggest a pancreatic beta cell tumor.
• D. This may suggest a deficiency in glycogen debrancher enzyme.

Answer: (B)

A reducing-substance test that is positive while the glucose dipstick is negative points to a sugar other than glucose being present in the urine. The most common and clinically important cause is galactose in the urine, seen in galactosemia. This occurs because of a deficiency in galactose-1-phosphate uridyl transferase, the enzyme that converts galactose-1-phosphate to UDP-galactose so galactose can be metabolized. When this enzyme is defective, galactose accumulates and is excreted in urine, producing a positive reducing-substance result, while glucose remains undetected by the glucose-specific dipstick.

A reducing-substance test that is positive while the glucose dipstick is negative points to a sugar other than glucose being present in the urine. The most common and clinically important cause is galactose in the urine, seen in galactosemia. This occurs because of a deficiency in galactose-1-phosphate uridyl transferase, the enzyme that converts galactose-1-phosphate to UDP-galactose so galactose can be metabolized. When this enzyme is defective, galactose accumulates and is excreted in urine, producing a positive reducing-substance result, while glucose remains undetected by the glucose-specific dipstick.