Study: 24-Hour Urine Collection Underused

VANCOUVER—High-risk stone formers seldom are asked for 24-hour urine collections, according to study findings presented at the 33rd Congress of the Societé Internationale d'Urologie.

Based on an analysis of medical claims from working-age adults, 24-hour urine collections were requested for only about 8% of patients at high risk of stone.

It is common for patients who suffer their first urinary stone to experience subsequent stone episodes. Consequently, secondary prevention has an important role, and this involves identifying and optimizing modifiable risk factors, researchers noted. The primary way to do this is with a 24-hour urine collection that is analyzed for various promoters and inhibitors of urinary stone formation. However, there have been no recommendations regarding 24-hour urine collections from U.S. professional organizations.

“While the prevalence of use is increasing over time, the overall rate of 24-hour urine testing is exceedingly low,” noted lead investigator John Hollingsworth, MD, MS.

Dr. Hollingsworth and his colleagues at the University of Michigan in Ann Arbor have adopted a protocol for evaluating stone-recurrence risk in first-time stone formers.

“Our protocol is based on risk stratification. For those without risk factors for recurrence, we perform screening blood work, and any abnormality prompts a 24-hour urine collection,” he told Renal & Urology News. “For high-risk patients, we now routinely ask them to complete a urine collection, and we make recommendations on diet/selective medical therapy based on the results.”

Dr. Hollingsworth's group also found that patients who had 24-hour urine testing were more likely than those who did not have the testing to be female, salaried, and living in an urban area. They also were more likely to have been seen by a urologist (75.3% vs. 45.9%) or a nephrologist (5.1% vs. 1.7%).

On multivariable analysis, patients seen by a urologist or nephrologist were nearly four times and three times, respectively, more likely to undergo 24-hour urine testing that those who were not.

In addition, patients aged 30 or older were 12% more likely to be tested than younger individuals. Women were 13% more likely than men to undergo testing. A Charlson score of zero or one was associated with an 84% and 70% increased likelihood of testing, respectively, compared with a Charlson score of 3.

“Providers may be motivated [by these results] to reduce the risk of stone recurrence in this subgroup [of higher Charlson scores, by conducting 24-hour urine testing] in order to spare them from the morbidity associated with the stone recurrence and the associated treatment,” Dr. Hollingsworth said.

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