Validation of a novel diagnostic test for assessing the risk of urinary uric acid crystallization

Background and aims: Uric acid (UA) kidney stones account for 10 to 11% of all kidney stones, and this percentage has increased over time. An accurate, rapid, simple, and low-cost test is needed to distinguish urine that is susceptible and resistant to the formation of UA crystals. The aim of this paper is to develop a test to assess the risk for UA crystallization (RUAC) and to validate its utility in routine clinical practice by analysis of urine samples of UA stone formers and healthy volunteers.

Patients and methods: Urine samples of 20 healthy adult volunteers and 54 active formers of UA stones were collected. Three samples were collected from each participant, with at least 7 days between each collection. The main lithogenic parameters for UA stones were determined, and an RUAC test was performed in all urine samples.

Results: Our RUAC test reliably discriminated urine that was resistant and susceptible to the formation of UA crystals. This test had high specificity (94%) and a low percentage of false negatives.

Conclusion: The RUAC test described here had high diagnostic accuracy, low-cost, and a rapid assay time, that make this test an attractive screening tool for UA stone fomers follow-up.