Twenty-Four Hour Urine Testing and Prescriptions for Urinary Stone Disease-Related Medications in Veterans

Abstract

Background and objectives: Current guidelines recommend 24-hour urine testing in the evaluation and treatment of persons with high-risk urinary stone disease. However, how much clinicians use information from 24-hour urine testing to guide secondary prevention strategies is unknown. We sought to determine the degree to which clinicians initiate or continue stone disease-related medications in response to 24-hour urine testing.

Design, setting, participants, & measurements: We examined a national cohort of 130,489 patients with incident urinary stone disease in the Veterans Health Administration between 2007 and 2013 to determine whether prescription patterns for thiazide diuretics, alkali therapy, and allopurinol changed in response to 24-hour urine testing.

Results: Stone formers who completed 24-hour urine testing (n=17,303; 13%) were significantly more likely to be prescribed thiazide diuretics, alkali therapy, and allopurinol compared with those who did not complete a 24-hour urine test (n=113,186; 87%). Prescription of thiazide diuretics increased in patients with hypercalciuria (9% absolute increase if urine calcium 201-400 mg/d; 21% absolute increase if urine calcium >400 mg/d, P<0.001). Prescription of alkali therapy increased in patients with hypocitraturia (24% absolute increase if urine citrate 201-400 mg/d; 34% absolute increase if urine citrate ≤200 mg/d, P<0.001). Prescription of allopurinol increased in patients with hyperuricosuria (18% absolute increase if urine uric acid >800 mg/d, P<0.001). Patients who had visited both a urologist and a nephrologist within 6 months of 24-hour urine testing were more likely to have been prescribed stone-related medications than patients who visited one, the other, or neither.

Conclusions: Clinicians adjust their treatment regimens in response to 24-hour urine testing by increasing the prescription of medications thought to reduce risk for urinary stone disease. Most patients who might benefit from targeted medications remain untreated.

Keywords: 24-hour urine; United States Department of Veterans Affairs; Veterans Health Administration; alkalies; allopurinol; calcium; citrates; citric acid; cohort studies; humans; hypercalciuria; kidney stones; medications; nephrologists; secondary prevention; sodium chloride symporter inhibitors; thiazides; uric acid; urinary calculi; urinary stone disease; urologists; veterans; veterans health.

Graphical abstract

Figure 1.

Comparison of observation periods between stone formers without and with 24-hour urine testing. For stone formers who did not complete 24-hour urine testing, we used the date of the initial stone diagnosis as a reference for comparison for the date of the initial 24-hour urine test in stone formers who completed 24-hour urine testing. We then compared filled prescriptions in the observation periods between stone formers with and without 24-hour urine testing.

Figure 2.

Thiazide prescriptions increase in the proportion of patients who excrete a higher level of urine calcium. Thiazide prescriptions in stone formers with 24-hour urine test, before and after 24-hour urine testing, stratified by level of 24-hour urine calcium excretion. *Difference in proportions before and after 24-hour urine test were significant at P<0.001. Δ, change.

Figure 3.

Alkali prescriptions increase in the proportion of patients who excrete a lower level of urine citrate. Alkali prescriptions in stone formers with 24-hour urine test, before and after 24-hour urine testing, stratified by level of 24-hour urine citrate excretion. Differences in proportions before and after 24-hour urine test were significant for all levels of 24-hour urine citrate excretion at P<0.001. Δ, change.

Figure 4.

Allopurinol prescriptions increase in the proportion of patients who excrete a higher level of urine uric acid. Allopurinol prescriptions in stone formers with 24-hour urine test and without gout, before and after 24-hour urine testing, stratified by level of 24-hour urine uric acid excretion. Differences in proportions before and after 24-hour urine test were significant for both levels of 24-hour urine uric acid excretion at P<0.001. Δ, change.