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目的评估氯离子清除试验在Gitelman综合征(GS)鉴别诊断中的应用价值。方法以临床低钾、碱中毒、疑诊为GS的患者为研究对象,提取外周血DNA进行SLC12A3基因筛查作为金标准。按照标准操作流程进行氢氯噻嗪试验和速尿试验,测定患者基线和用药后3 h内氯离子排泄分数改变量的最大值(ΔFECl),评价对氢氯噻嗪和速尿的反应性,并与健康受试者比较,绘制受试者工作特征(ROC)曲线确定ΔFECl绝对值和相对值诊断GS的截点,计算氯离子清除试验诊断GS的灵敏度和特异度。结果 27例患者和20例健康受试者进行了氢氯噻嗪试验。以SLC12A3基因检测为诊断金标准,23例患者被诊断为GS。以ΔFECl绝对值和相对值诊断GS的ROC曲线下面积分别为0.987(95%CI:0.963~1.000,P<0.001)和0.984(95%CI:0.950~1.000,P<0.001)。选择适当的截点,灵敏度和特异度均达到95%以上。8例患者同时完成了氢氯噻嗪试验和速尿试验,其中5例患者对氢氯噻嗪无反应(ΔFECl绝对值≤2.86%或相对值≤223%),对速尿反应敏感,同时存在SLC12A3基因突变,确诊为GS;3例患者对氢氯噻嗪反应敏感,而使用速尿后FECl改变不明显,基因测序除外GS,考虑Bartter综合征可能性大。结论临床上综合应用氢氯噻嗪试验和速尿试验观察氯离子排泄分数的变化能有效鉴别GS和BS患者。
Objective To evaluate the value of chloride ion scintigraphy in the differential diagnosis of Gitelman’s syndrome (GS). Methods Patients with clinical hypokalemia and alkalosis who were suspected to be GS were selected as the gold standard for screening of SLC12A3 gene from peripheral blood DNA. Hydrochlorothiazide test and furosemide test were performed in accordance with standard operating procedures. The maximum value of change in chloride excretion fraction (ΔFEC1) at baseline and within 3 h after treatment was measured to evaluate the reactivity toward hydrochlorothiazide and furosemide and compared with healthy subjects The receiver operating characteristic (ROC) curve was plotted to determine the absolute and relative value of ΔFECl to diagnose the intercept of GS and to calculate the sensitivity and specificity of the chloride clearance test to diagnose GS. Results Hydrochlorothiazide was tested in 27 patients and 20 healthy subjects. To SLC12A3 gene test for the gold standard, 23 patients were diagnosed with GS. The area under the ROC curve for diagnosis of GS with absolute and relative ΔFECl values was 0.987 (95% CI: 0.963-1.000, P <0.001) and 0.984 (95% CI: 0.950-1.000, P <0.001), respectively. Select the appropriate cut-off point, sensitivity and specificity of more than 95%. Eight patients completed hydrochlorothiazide and furosemide simultaneously. Five of them had no response to hydrochlorothiazide (ΔFECl ≤2.86% or relative ≤223%) and were sensitive to furosemide with SLC12A3 gene mutation identified as GS; three patients were sensitive to hydrochlorothiazide, and the use of furosemide FECl change was not obvious, except for gene sequencing GS, considering the possibility of Bartter syndrome. Conclusions The clinical application of hydrochlorothiazide test and furosemide test to observe the change of chloride ion excretion fraction can effectively identify patients with GS and BS.