da Costa Brito Maria Paula, Picard Kelly, Simas Torres Klein Márcia Regina, Lysandro Rodrigues Gomes Conrado, Bregman Rachel, Barreto Silva Maria Inês
Post Graduation Program in Medical Science, Rio de Janeiro State University, Rio de Janeiro, 20550-900, Brazil.
Island Health Authority and British Columbia Renal Agency, Nanaimo, British Columbia, Canada.
Clin Nutr ESPEN. 2025 Apr;66:24-33. doi: 10.1016/j.clnesp.2025.01.020. Epub 2025 Jan 10.
BACKGROUND & AIMS: In the general population, 24-h urine potassium excretion is considered the reference standard for estimating potassium intake. However, its agreement with food records and spot urine collections in adults living with chronic kidney disease (CKD) is not well-established. Given the risk of hyperkalemia related to changes in renal potassium handling, understanding if this reference standard is appropriate for the CKD population is important. This study aimed to compare agreement between methods for estimating potassium intake, using food records, 24-h urine measures, and spot urine samples.
A cross-sectional study was conducted among adults recruited from a kidney care clinic. Participants were instructed to complete a detailed food record and a 24-h urine collection, both performed on the same day. The following day, participants provided a spot urine sample from the second void, at the research site. Potassium excretion was estimated from the spot urine sample using Tanaka's and Kawasaki's equations. Agreement between methods was assessed using the highest p-value for paired t-test and the lowest Bland-Altman bias combined with the narrowest upper and lower limits of agreements (LoA).
60 adults with Stage 3 and 4 CKD completed the study (48 % male, 62.9 ± 14.6 years; eGFR = 34.9 ± 12.7 mL/min). The food records showed the highest agreement with 24-h urine potassium (1823.9 ± 746.7 vs 1918.2 ± 809.3, p = 0.584). This was followed by Kawasaki's equation for spot urine (1994.8 ± 441.9, p = 0.231) and Tanaka's equation (1630.0 ± 325.9, p = 0.174). Food records and Kawasaki's equation had slightly higher mean values compared to 24-h urine with mean differences <100-200 mg/day (bias; 95%CI: bias = -94.4 mg/day; -438.3 to 249.6 mg/day and -170.9 mg/day; -454.1 to 112.2 mg/day, respectively). Tanaka's equation had a lower mean value compared to 24-h urine with a mean difference of 193.9 mg/day; -88.5 to 476.3 mg/day). The limits of agreement were as follows: in the Kawasaki's equation from -2082.2 to 1740.3 mg/day, in the Tanaka's equation from -1712.2 to 2100.0 mg/day and in the food records from -2416.1 to 2227.4 mg/day.
Mean potassium intake estimates were similar across methods. Food records demonstrated the highest agreement with 24-h urine potassium, followed by Kawasaki's equation. The Tanaka's equation showed the highest bias compared to 24-h urine and was significantly different from food records. Combining food records with potassium excretion estimated using the Kawasaki's equation from spot urine samples may be a clinically useful tool for assessing potassium intake in adults with CKD.
在普通人群中，24小时尿钾排泄量被视为估算钾摄入量的参考标准。然而，对于慢性肾脏病（CKD）成年患者，其与食物记录及随机尿样采集结果的一致性尚未明确。鉴于肾钾处理变化相关的高钾血症风险，了解该参考标准对CKD人群是否适用十分重要。本研究旨在比较采用食物记录、24小时尿测量及随机尿样估算钾摄入量方法之间的一致性。
对从肾脏护理诊所招募的成年患者进行横断面研究。参与者被要求在同一天完成详细的食物记录和24小时尿液采集。次日，参与者在研究地点提供第二次排尿的随机尿样。使用田中方程和川崎方程从随机尿样中估算钾排泄量。采用配对t检验的最高p值以及最低的布兰德-奥特曼偏差并结合最窄的一致性界限（LoA）评估各方法之间的一致性。
60例3期和4期CKD成年患者完成了研究（48%为男性，年龄62.9±14.6岁；估算肾小球滤过率[eGFR]=34.9±12.7 mL/分钟）。食物记录与24小时尿钾的一致性最高（分别为1823.9±746.7与1918.2±809.3，p=0.584）。其次是川崎方程估算的随机尿样结果（1994.8±441.9，p=0.231）以及田中方程估算的结果（1630.0±325.9，p=0.174）。与24小时尿样相比，食物记录和川崎方程的平均值略高，平均差异<100 - 200毫克/天（偏差；95%置信区间：偏差分别为-94.4毫克/天；-438.3至249.6毫克/天以及-170.9毫克/天；-454.1至112.2毫克/天）。田中方程估算的平均值低于24小时尿样，平均差异为193.9毫克/天；-88.5至476.3毫克/天）。一致性界限如下：川崎方程为-2082.2至1740.3毫克/天，田中方程为-1712.2至2100.0毫克/天，食物记录为-2416.1至2227.4毫克/天。
各方法估算的平均钾摄入量相似。食物记录与24小时尿钾的一致性最高，其次是川崎方程。与24小时尿样相比，田中方程偏差最大，且与食物记录有显著差异。将食物记录与使用川崎方程从随机尿样估算的钾排泄量相结合，可能是评估CKD成年患者钾摄入量的一种临床有用工具。
