Association Between Dietary Potassium Intake Estimated From Multiple 24-Hour Urine Collections and Serum Potassium in Patients With CKD

Introduction: Limited and inconclusive evidence for the association of dietary potassium intake with serum potassium in chronic kidney disease (CKD) patients have been shown, though restricting dietary potassium has been recommended for CKD patients to prevent hyperkalemia. Multiple 24-hour urine collections are necessary to adequately assess potassium intake. We investigated associations of 24-hour urinary potassium excretion (UKV) with serum potassium in CKD outpatients based on multiple 24-hour urine collections. Methods: This retrospective cohort study was based on outpatients with CKD stages G3 to G5, median age of 72.0 years; and median follow-up of 3.9 months and 8.9 months, respectively, for analyses using 3-time measurement (N = 290 and 870 observations) and 7-time measurements (N = 220 and 1540 observations). The outcome was serum potassium. Results: Multivariable-adjusted mean difference in serum potassium (mEq/l) and odds ratio of hyperkalemia per 10 mEq/d increase in UKV were, respectively, 0.12 (95% confidence interval [CI]: 0.09–0.15) and 2.15 (1.70–2.73) in generalized estimating equations (GEEs) with 3-time measurements. The mean difference became more pronounced as CKD stages progressed: 0.08 (0.05–0.12), 0.12 (0.08–0.16), and 0.16 (0.12–0.20) for CKD G3, G4, and G5. Similar results were obtained from analyses using 7-time measurements and hierarchical Bayesian measurement error models treating measurement error of UKV adequately. Conclusion: We suggest significant but weak associations (R²: 0.08, 0.14, and 0.18 for CKD G3, G4, and G5) between serum potassium and dietary potassium intake estimated by multiple 24-hour urine collections in CKD patients. Further studies are needed to validate nutritional and clinical aspects of the associations.