Reducing substances in urine: a paradigm for changes in a standard test

Area of Science:

• Clinical Chemistry
• Biochemistry
• Pediatric Diagnostics

Background:

• Detection of reducing substances in urine is a long-standing laboratory test.
• This test is historically used for screening inborn errors of carbohydrate metabolism.
• Despite advancements and mandatory newborn screening, it persists as a reflex test in many labs.

Purpose of the Study:

• To evaluate the continued clinical utility of detecting reducing substances in pediatric urine samples.
• To recommend changes in laboratory testing protocols for this analyte.
• To encourage a review of laboratory test menus for relevance.

Main Methods:

• Review of historical and current laboratory practices.
• Analysis of the specificity and clinical rationale for the reducing substances test.
• Assessment of the impact of mandatory newborn screening programs.

Main Results:

• The test for reducing substances in urine exhibits poor specificity.
• Most common genetic defects are now covered by mandatory newborn screening.
• The test is often performed as a reflex test without specific physician orders.

Conclusions:

• The routine, reflex testing for reducing substances in urine lacks strong clinical rationale.
• Laboratories should transition to physician-ordered testing for reducing substances.
• Regular review and culling of the test menu are essential for modern clinical laboratories.