Prevalence of 24-hour urine collection in high risk stone formers

Secondary prevention has an important role in urinary stone disease. The core of secondary prevention is the identification of modifiable risk factors by a 24-hour urine collection, which then directs selective medical therapy. While this decreases the recurrence rate, little is known about the frequency with which 24-hour urine collections are obtained.

Using medical claims from 2002 to 2006 we identified adults with incident urinary stone episodes. With appropriate diagnosis codes we determined those at high risk for recurrence. Of these patients we determined the proportion in whom a 24-hour urine collection was done within 6 months of diagnosis. Finally, we fitted regression models to measure associations between patient and provider level factors, and obtaining a 24-hour urine collection.

We identified 28,836 patients at high risk for recurrence. The prevalence of 24-hour urine testing increased from 7.0% in 2003 to 7.9% in 2006 (p = 0.011), although the overall prevalence was exceedingly low at 7.4%. Multivariable regression revealed that region of residence and level of comorbid illness were independently associated with 24-hour urine collection, as was the type of physician who performed the followup. For instance, the odds of metabolic evaluation were 2.9 times higher when a patient was seen by a nephrologist (OR 2.92, 95% CI 2.32-3.67), and more than threefold higher when seen by a urologist (OR 3.87, 95% CI 3.48-4.30).

Obtaining 24-hour urine collections in stone formers at high risk is uncommon, raising a quality of care concern.