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Application Value of Random Urine Potassium-to-Creatinine Ratio in Diagnosing Renal Potassium Loss
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摘要:
目的 分析随机尿钾/尿肌酐（rUK/Ucr）在判断肾性失钾中的应用价值。 方法 纳入2017–2021年诊断为低钾血症患者〔包括肾性失钾（373例）、非肾性失钾（83例）〕、血钾正常（358例）的住院患者。收集临床资料，分析rUK/Ucr与24 h尿钾（24 hUK）的相关性；针对低钾血症患者绘制受试者工作特征（ROC）曲线，分析rUK/Ucr判断肾性失钾的价值。 结果 血钾在血钾正常组、肾性失钾组、非肾性失钾组依次降低（P<0.01）。肾性失钾组24 hUK、rUK/Ucr大于非肾性失钾及血钾正常组（P<0.01）。rUK/Ucr与24 hUK呈低到中度相关。24 hUK、rUK/Ucr判断肾性失钾的曲线下面积（AUC）分别为0.73、0.71，rUK/Ucr判断肾性失钾的最佳切点为3.4时，灵敏度为67.59%，特异度为67.53%。 结论 rUK/Ucr与24 hUK的相关性一般，rUK/Ucr预测肾性失钾的价值与24 hUK相当。在无法获取24 h尿液标本时，可推荐使用rUK/Ucr替代24 hUK来初步判断是否存在肾性失钾，其最佳诊断切点为3.4。 Abstract:Objective To analyze the value of applying random urine potassium-to-creatinine ratio (rUK/Ucr) in diagnosing renal potassium loss. Methods patients diagnosed with hypokalemia, including 373 cases of renal potassium loss, 83 cases of non-renal potassium loss , and 358 cases of normal serum potassium, between 2017 and 2021 were enrolled. The clinical data of the patients were collected and the correlation between rUK/Ucr and 24-hour urine potassium (24 hUK) in the three groups was analyzed. The receiver operating characteristic (ROC) curve was used to analyze the value of applying rUK/Ucr in diagnosing renal potassium loss. Results Serum potassium decreased in the normal serum potassium group, the renal potassium loss group, and the non-renal renal potassium loss group (P<0.01). The 24 hUK and the rUK/Ucr of the renal potassium loss group were higher than those of the non-renal potassium loss group and normal serum potassium group (P<0.01). rUK/Ucr showed low to moderate correlation with 24 hUK. The AUC of 24 hUK and rUK/Ucr for determining renal potassium loss were 0.73 and 0.71, respectively. When the optimal cutoff point of rUK/Ucr for determining renal potassium loss was 3.4, the sensitivity was 67.6% and the specificity was 67.5%. Conclusion rUK/Ucr shows a moderate correlation with 24 hUK and its accuracy in determining renal potassium loss is comparable to that of 24 hUK. When 24-hour urine samples cannot be obtained, it is recommended that rUK/Ucr be used instead of 24 hUK to determine whether renal potassium loss exists, with the optimal cutoff point for diagnosis being 3.4. -
图 1 rUK/Ucr及24 hUK判断肾性失钾的ROC曲线图
Figure 1. ROC curves of rUK/Ucr and 24 hUK for renal potassium loss
表 1 血钾正常组、肾性失钾组、非肾性失钾组之间临床生化指标的差异性比较
Table 1. The differences in clinical biochemical indices among normal potassium group, renal potassium loss group, and non-renal potassium loss group
Index Normal potassium group (n=358) Renal potassium loss group (n=373) Non-renal potassium loss group (n=83) Male/% 46.09 49.33 38.55 Age/yr. 50.30±14.81 50.64±12.45 48.02±9.57 BMI/(kg/m2) 24.46±3.82 24.61±3.78 24.00±3.04 SBP/mmHg 158±32 174±26**, †† 163±30 DBP/mmHg 96±22 106±16** 100±23 Synchronous potassium/(mmol/L) 3.98±0.30 3.20±0.20** 2.55±0.19**, †† Glu/(mmol/L) 5.0 (4.5, 6.1) 5.0 (4.6, 5.6) 5.7 (4.9, 8.8)**, †† TC/(mmol/L) 4.44±1.10 4.28±0.89*, † 4.31±0.81 TG/(mmol/L) 1.3 (1.0, 2.0) 1.3 (0.8, 1.8) 1.5 (0.9, 2.3) LDL-C/(mmol/L) 2.59±0.86 2.47±0.80 2.60±0.61 eGFR/(mL/[min·1.73 m2]) 98.75±20.93 98.27±21.38 97.37±23.49 Synchronous 24 hUK/mmol 37.8 (29.3, 49.3) 45.3 (34.7, 61.2)** 31.4 (24.4, 38.0)**, †† rUK/Ucr 3.5 (2.5, 4.8) 4.2 (3.0, 6.5)** 2.9 (2.1, 4.0)*, †† * P<0.05, ** P<0.01, vs. normal potassium group; † P<0.05, †† P<0.01, vs. renal potassium loss group. 1 mmHg=0.133 kPa. BMI: body mass index; SBP: systolic blood pressure; DBP: diastolic blood pressure; Glu: glucose; TC: total cholesterol; TG: triglyceride; LDL-C: low density lipoprotein cholesterol; eGFR: estimated glomerular filtration rate. 
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表 2 rUK/Ucr与24 hUK的Spearman相关分析
Table 2. The Spearman correlation between rUK/Ucr and 24 hUK
Group Spearman r Total (n=814) 0.46 Serum potassium/(mmol/L) ≥3.5 (n=358) 0.46 <3.5 (n=456) 0.46 3-3.49 (n=298) 0.46 <3 (n=158) 0.39 Renal potassium loss Yes (n=373) 0.45 No (n=83) 0.66
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表 3 rUK/Ucr、24 hUK诊断肾性失钾的ROC曲线参数
Table 3. Parameters of ROC curves for the rUK/Ucr and 24 hUK
Parameter 24 hUK rUK/Ucr AUC 0.73 0.71 Optimum cutoff point 38 3.4 Sensitivity 64.44% 67.56% Specificity 75% 67.53% False positive rate 25% 32.74% False negative rate 35.56% 32.41% Positive likelihood ratio 2.58 2.08 Negative likelihood ratio 0.47 0.48 Positive predictive value 91.38% 85.38% Negative predictive value 33.9% 42.62% Accuracy 66.5% 67.58% AUC: area under the curve.
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