NEW YORK (Reuters Health) – The mineral composition of kidney stones reported by commercial laboratories is often inaccurate, investigators at Indiana University, Indianapolis report in the Journal of Urology for October.

They point out that these errors have implications for preventing recurrence in metabolic stone disease and for clinical management of infection stones.

Dr. James C. Williams, Jr. and colleagues determined the composition of 25 renal stones by infrared spectroscopy and then sent fragmented samples to five commercial laboratories for blinded analysis.

“Generally the laboratories in our study accurately reported the composition of relatively pure stones. However, results were concerning in regard to reporting struvite and mixed stones,” the team found.

Specifically, struvite was identified correctly by all the labs in only two of four stones known to contain the compound, while some labs reported struvite in four stones that did not contain it.

“A report of struvite in stones can often guide postoperative treatment,” the authors explain. “It is generally recommended that patients receive a prolonged course of antibiotic therapy if they had struvite containing stones, even after complete stone clearance is achieved.”

Other errors included a stone known to contain the antiviral drug atazanavir, which was missed by all five laboratories.

In another example, apatite in six apatite-containing stones was missed by the laboratories in 20% of samples, according to the report.

As another potential complication, the researchers note there was no standard nomenclature among the laboratories.

Dr. Williams and colleagues conclude, “These findings call for further investigation of stone analysis procedures and reporting, and for the development of a standardized analysis/reporting protocol.”

Reference:

Inaccurate Reporting of Mineral Composition by Commercial Stone Analysis Laboratories: Implications for Infection and Metabolic Stones

J Urol 2010;184:1543-1549.