Overview

The Urine Reducing Substance (R/S) Test detects the presence of reducing sugars (e.g., glucose, galactose, lactose, fructose) in urine. This test is mainly used to screen for conditions like diabetes, inborn errors of metabolism (e.g., galactosemia), and malabsorption syndromes.

Risk Assessment & Indications for the Test

This test may be ordered if a patient has symptoms such as:

• Frequent urination (polyuria)
• Excessive thirst (polydipsia)
• Unexplained weight loss
• Diarrhea or vomiting in infants (to check for metabolic disorders)
• Failure to thrive in newborns

It is particularly useful in diagnosing:

• Diabetes mellitus (if glucose is present)
• Lactose intolerance
• Galactosemia (especially in infants)
• Fructosuria or other carbohydrate metabolism disorders.

Normal Range

• Negative (No detectable reducing substances)
• Trace amounts may be seen in some healthy individuals (not clinically significant).

Interpretation of Results

• Negative: No reducing substances detected (normal).
• Positive: Presence of reducing substances (requires further testing to determine the specific sugar).

A positive test may indicate:

1. Glucose → Suggests diabetes mellitus or renal glycosuria.
2. Galactose → Suggests galactosemia (common in infants).
3. Fructose → Indicates essential fructosuria.
4. Lactose → Could be due to lactose intolerance.

For confirmation, further tests like Benedict’s test, glucose oxidase test, or chromatography may be done to identify the specific sugar.

Sample Type & Collection

• Sample Type: Urine (Random or 24-hour collection)
• Container: Sterile urine container
• Methodology: Benedict’s test or Clinitest (Copper reduction method)
• Special Instructions:
  • For infants, a fresh urine sample is preferred.
  • Avoid contamination with sugar-containing substances.