The Role of Race in Determining 24-Hour Urine Composition in White and Asian/Pacific Islander Stone Formers

Purpose: We examined differences in 24-hour urine composition between white and Asian/Pacific Islander stone formers. Materials and Methods: We retrospectively reviewed the 24-hour urinalysis database at a metabolic stone clinic. We identified and included in the study patients 18 years old or older who presented for the initial metabolic stone evaluation when race was marked as white or Asian/Pacific Islander in the electronic medical record. Univariate analysis was done to compare 24-hour urine composition between white and Asian/Pacific Islander stone formers. We performed multivariate linear regression adjusted for possible confounders, including age, gender, body mass index, hypertension, diabetes mellitus, thiazide use, potassium citrate use and 24-hour urine chemistry (volume, pH, calcium, citrate, creatinine, oxalate, magnesium, phosphate, potassium, sodium, sulfate and uric acid). Results: Included in analysis were 371 white and 91 Asian/Pacific Islander patients. On univariate analysis Asian/Pacific Islander patients excreted significantly greater uric acid, and significantly less citrate, magnesium, phosphate and creatinine than white patients. On multivariate analysis Asian/Pacific Islander patients excreted significantly greater uric acid, and significantly less urine citrate, phosphate, creatinine and volume than white patients. Conclusions: Significant differences exist in 24-hour urine chemistry between white and Asian/PI stone formers. Knowledge of these differences would be useful to evaluate and treat these patients, and prevent stone recurrence.