尿标本参数对低钾血症肾性失钾的诊断价值。

Diagnostic value of parameters from a spot urine sample for renal potassium loss in hypokalemia.

机构信息

Department of Endocriology, The Affiliated Hospital of Southwest Medical University, Luzhou, 646000 Sichuan, China.

出版信息

Clin Chim Acta. 2020 Dec;511:221-226. doi: 10.1016/j.cca.2020.10.024. Epub 2020 Oct 20.

DOI:10.1016/j.cca.2020.10.024

PMID:33096028

Abstract

BACKGROUND

We assessed the value of 1) a spot urine test for diagnosing hypokalemia caused by renal potassium loss, and 2) actual 24-hour urine potassium excretion (24 hUK-actual) for diagnosing hypokalemia caused by renal potassium loss in patients treated with potassium supplementation. The study population was from Southwest China.

METHODS

Patients with hypokalemia were divided into 2 groups: hypokalemia caused by renal potassium loss (n = 67) and hypokalemia caused by extrarenal potassium loss (n = 63). Urine potassium concentration (UK), urine creatinine concentration (UCr), urine potassium-creatinine ratio (UK/UCr), fractional excretion of potassium (FEK), transtubular potassium concentration gradient (TTKG), and 24-h urine potassium excretion (24 hUK-calculated) were derived from spot urine samples collected on admission, before initiation of therapy. Patients received intravenous potassium chloride 0.4 or 0.6 g/h. 24 hUK-actual was detected in patients whose serum potassium did not return to normal after 24 h of therapy.

RESULTS

Patients with hypokalemia caused by renal potassium loss had significantly higher UK, UK/UCr, FEK, TTKG and 24 hUK-calculated compared to patients with hypokalemia caused by extrarenal potassium loss (P < 0.05). FEK predicted renal potassium loss in hypokalemia with high accuracy at a cut-off of 9.29% (sensitivity, 80.6%; specificity, 85.7%). The area under the curve for 24 hUK-actual in predicting renal potassium loss in patients with hypokalemia treated with low or high-dose potassium chloride infusion were 0.939 or 0.956, respectively. On the spot urine test, FEK showed the highest correlation with 24 hUK-actual during low or high dose potassium chloride infusion (r = 0.831, p < 0.001 or r = 0.764, p < 0.001).

CONCLUSIONS

FEK from a spot urine sample represents a convenient and reliable parameter to predict renal potassium loss in patients with hypokalemia.

摘要

背景

我们评估了 1）用于诊断由肾性钾丢失引起的低血钾症的即时尿检测，以及 2）实际 24 小时尿钾排泄（24 hUK-actual）在接受钾补充治疗的患者中诊断由肾性钾丢失引起的低血钾症的价值。研究人群来自中国西南地区。

方法

将低血钾症患者分为 2 组：由肾性钾丢失引起的低血钾症（n=67）和由肾外钾丢失引起的低血钾症（n=63）。入院时、开始治疗前采集即时尿样，计算尿钾浓度（UK）、尿肌酐浓度（UCr）、尿钾肌酐比值（UK/UCr）、钾排泄分数（FEK）、跨小管钾浓度梯度（TTKG）和 24 小时尿钾排泄（24 hUK-calculated）。在治疗 24 小时后血清钾未恢复正常的患者中检测实际 24 小时尿钾排泄（24 hUK-actual）。

结果

由肾性钾丢失引起的低血钾症患者的 UK、UK/UCr、FEK、TTKG 和 24 hUK-calculated 明显高于由肾外钾丢失引起的低血钾症患者（P<0.05）。FEK 在预测低血钾症中的肾性钾丢失时具有高准确性，截断值为 9.29%（敏感性为 80.6%，特异性为 85.7%）。在接受低剂量或高剂量氯化钾输注的低血钾症患者中，24 hUK-actual 预测肾性钾丢失的曲线下面积分别为 0.939 或 0.956。在即时尿检测中，FEK 在低剂量或高剂量氯化钾输注期间与 24 hUK-actual 的相关性最高（r=0.831，p<0.001 或 r=0.764，p<0.001）。