Comparison of 24-h Urinary Aldosterone Level and Random Urinary Aldosterone-to-Creatinine Ratio in the Diagnosis of Primary Aldosteronism

BackgroundHistorically, urinary aldosterone level measurement was a commonly employed confirmatory test to detect primary aldosteronism (PA). However, 24-h urine collection is inconvenient and cumbersome. We hypothesized that random urinary aldosterone measurements with correction for creatinine concentration might be comparable to 24-h urinary aldosterone levels (Uald-24 h) in the diagnosis of PA.MethodsThe non-concurrent prospective study was conducted between June 2006 and March 2008 in patients admitted for confirmation of aldosteronism by salt loading test. A 24-h urine sample, which was collected during hospitalization on the day before saline infusion testing after restoration of serum hypokalemia, was collected from all subjects. Moreover, participants were asked to collect a first bladder voiding random urine sample during clinic visits. Uald-24 h and the random urinary aldosterone-to-creatinine ratio (UACR) were calculated accordingly.ResultsA total of 102 PA patients (71 patients diagnosed of aldosterone-producing adenoma, 31 with idiopathic hyperaldosteronism) and 65 patients with EH were enrolled. The receiver operating characteristic curve showed comparable areas under the curves of UACR and Uald-24 h. The Bland-Altman plot showed mean bias but no obvious heteroscedasticity between the two tests. When using random UACR >3.0 ng/mg creatinine as the cutoff value, we obtained a specificity of 90.6% to confirm PA from essential hypertension.ConclusionsOur study reinforce that the diagnostic accuracy of random UACR was comparable to that of Uald-24 h in PA patients. With the quickness and simplicity of the UACR method and its equivalence to Uald-24 h, this assay could be a good alternative diagnostic tool for PA confirmation.

背景：长期以来，尿醛固酮水平检测是确诊原发性醛固酮增多症（primary aldosteronism, PA）的常用确证试验。然而，24小时尿标本留取操作繁琐且不便实施。我们推测，经肌酐浓度校正的随机尿醛固酮检测，在PA诊断中可与24小时尿醛固酮水平（Uald-24 h）相媲美。
方法：本研究为非同期前瞻性研究，于2006年6月至2008年3月期间开展，纳入因盐负荷试验确诊醛固酮增多症而入院的患者。所有受试者均于住院期间，在血清低钾血症纠正后、盐水输注试验前一日留取24小时尿标本。此外，要求受试者在门诊就诊时留取首次排尿的随机尿标本。随后分别计算Uald-24 h及随机尿醛固酮/肌酐比值（random urinary aldosterone-to-creatinine ratio, UACR）。
结果：共纳入102例PA患者（其中71例为醛固酮瘤患者，31例为特发性醛固酮增多症患者）及65例原发性高血压（essential hypertension, EH）患者。受试者工作特征曲线（receiver operating characteristic curve, ROC）结果显示，UACR与Uald-24 h的曲线下面积无显著差异。布兰德-奥特曼图显示两种检测方法间存在平均偏差，但无明显异方差性。当以随机UACR＞3.0 ng/mg肌酐作为截断值时，从原发性高血压患者中确诊PA的特异性可达90.6%。
结论：本研究证实，在PA患者中，随机UACR的诊断准确性与Uald-24 h相当。鉴于UACR检测方法简便快捷，且与Uald-24 h检测结果等效，该方法可作为PA确诊的良好替代诊断工具。