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Abstract: SA-PO303

Adherence to Potassium Citrate and Changes in 24-Hour Urine Stone Risk Parameters

Session Information

Category: Bone and Mineral Metabolism

  • 502 Bone and Mineral Metabolism: Clinical

Authors

  • Crivelli, Joseph J., The University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States
  • Oerline, Mary K., University of Michigan Medical School, Ann Arbor, Michigan, United States
  • Hsi, Ryan, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
  • Smith, Kevin, University of Michigan College of Engineering, Ann Arbor, Michigan, United States
  • Denton, Brian, University of Michigan College of Engineering, Ann Arbor, Michigan, United States
  • Asplin, John R., Laboratory Corporation of America Holdings, Burlington, North Carolina, United States
  • Shahinian, Vahakn, University of Michigan Medical School, Ann Arbor, Michigan, United States
  • Hollingsworth, John M., NorthShore University HealthSystem, Evanston, Illinois, United States
Background

Patient adherence to potassium citrate therapy for urinary stone disease (USD) is low. We assessed associations of potassium citrate adherence with changes in 24-hour urine parameters.

Methods

We identified adults enrolled in Medicare with USD, a baseline 24-hour urine collection (Litholink, 2011-2017), hypocitraturia or low urine pH, a prescription for monotherapy with potassium citrate tablets within 3 months, and a follow-up urine collection 6-12 months after baseline. We defined two measures of adherence: (1) percentage of days covered (PDC) over 0-3 months based on pharmacy claims and (2) change in urinary potassium (ΔK) between baseline and follow-up. We assessed the association between PDC and ΔK using an independent t-test and the association of adherence with changes in urinary citrate and pH using ANCOVA. Finally, we compared the strength of association of PDC and ΔK with these changes using a Wald test.

Results

Among 432 patients, 366 (85%) had hypocitraturia and 266 (62%) had low urine pH. Patients adherent to medication based on pharmacy claims (PDC≥80%) had a significantly higher mean ΔK compared to those not adherent to medication (+26.1 mEq/day vs. +17.9 mEq/day, P<0.001). The adjusted mean increase in urinary citrate and pH among patients adherent to medication significantly exceeded that of patients not adherent to medication (Figure). Compared to PDC, ΔK had a stronger association with change in urinary citrate (P<0.001) and pH (P=0.07), though the latter was not statistically significant.

Conclusion

Compared to pharmacy claims, the increase in urinary potassium was generally more predictive of increased urinary citrate and pH, emphasizing the value of urinary potassium as a measure of adherence.

Mean change in (A) urinary citrate and (B) pH stratified by adherence. Estimates are adjusted for age, sex, race, region of residence, dual eligibility, comorbidity score, and medication dose. Error bars represent 95% CIs.

Funding

  • NIDDK Support