Racial and Demographic Variables Are Associated with Accurate 24-hour Urine Collection Completion and Results

To understand and evaluate demographic predictors of accurate urine collection, as well as to detail key racial differences in lithogenic urine markers.

We retrospectively reviewed stone-forming patients who underwent 24-hour urine collection between 2010-2022 at a tertiary center. Accuracy was defined by Mayo Clinic creatinine thresholds (13-29 mg/kg for males; 9-26 mg/kg for females). Multivariable logistic regression assessed predictors of accurate collection and racial associations with urinary abnormalities, adjusting for age ≥55, sex, and obesity.

Of 823 patients, 694 (84.3%) collected accurately. Age ≥55 years was associated with double the odds of accuracy (OR 2.18, 95%CI 1.44-3.31, P <.001). Male sex (OR 0.49, 95%CI 0.32-0.76, P = .001) and Black race (OR 0.51, 95%CI 0.32-0.81, P = .005) predicted lower accuracy. Among accurate completers, Black patients had lower odds of hypercalciuria (OR 0.32, P <.001), hyperphosphaturia (OR 0.28, P <.001), and calcium phosphate supersaturation (OR 0.45, P = .022), but higher odds of hypercitraturia (OR 1.69, P = .008).

Younger age, male sex, and Black race were associated with reduced 24-hour urine collection accuracy, highlighting the need for targeted education. Among accurate completers, Black patients demonstrated distinct urinary profiles suggestive of reduced risk for calcium-based stones. These findings highlight the importance of improving adherence and incorporating racial differences into individualized nephrolithiasis risk assessment.