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Updated: Jan 11, 2026

Estimation of Urinary Nanocrystals in Humans using Calcium Fluorophore Labeling and Nanoparticle Tracking Analysis
Published on: February 9, 2021
Urine Uric Acid Pseudodeficiency from Urate Crystallization: a Pre-Analytical Laboratory Pitfall
Background:
Pre-analytical factors like improper urine storage may distort uric acid measurements. This case demonstrates how refrigeration-induced urate crystallization causes falsely low urine uric acid (UUA), complicating hyperuricemia management.
Methods:
A 61-year-old diabetic male with normal serum uric acid (221 µmol/L) showed discordant UUA results (initial: 6,823 µmol/L vs. repeat: 3,500 µmol/L). Laboratory tests assessed pH adjustment, temperature effects, and 24-hour UUA to identify crystallization interference.
Results:
Refrigeration reduced UUA by 48.7%. NaOH-mediated pH adjustment (pH 8.0) dissolved crystals, restoring UUA to 8,826 µmol/L. 24-hour UUA (3,756 µmol/24 hour) aligned with clinical expectations. Temperature and pH critically impacted urate solubility.
Conclusions:
Urate crystallization causes UUA pseudodeficiency. Laboratories should prioritize immediate testing or pH adjustment. Clinicians must recognize pre-analytical pitfalls to avoid diagnostic misclassification.
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