尿崩症患者血浆渗透压变化，诊断性试验-Copeptin在诊断尿崩症中的应用

BACKGROUND

The indirect water-deprivation test is the current referencestandard for the diagnosis of diabetes insipidus. However, it is technicallycumbersome to administer, and the results are often inaccurate. The current study compared the indirectwater-deprivation test with direct detection of plasma copeptin, a precursor-derived surrogate of arginine vasopressin.

间接缺水试验是目前诊断尿崩症的参考标准。然而，管理在技术上很麻烦，结果往往是不准确的。目前的研究比较了间接水剥夺试验和血浆和肽素的直接检测，血浆和肽素是精氨酸加压素的前体衍生物替代物。

METHODS

From 2013 to 2017, we recruited 156 patients with hypotonicpolyuria at 11 medical centers to undergo both water-deprivation and hypertonicsaline infusion tests. In the latter test, plasma copeptin was measured whenthe plasma sodium level had increased to at least 150 mmol per liter afterinfusion of hypertonic saline. Theprimary outcome was the overall diagnostic accuracy of each test as compared with the finalreference diagnosis,which was determined on the basis of medical history, test results, andtreatment response, with copeptin levels masked.

从2013年到2017年，我们在11个医疗中心招募了156名低渗性多尿患者，进行缺水和高渗盐水输注试验。在后一种试验中，当输注高渗盐水后血浆钠水平增加至至少150mmol / L时，测量血浆和肽素。 主要结果是每个测试的总体诊断准确性与最终参考诊断相比，最终参考诊断是根据病史，测试结果和治疗反应确定的，其中隐蔽了copeptin水平。

RESULTS

A total of 144 patients underwent both tests. The final diagnosis was primary polydipsia in82 patients (57%), central diabetes insipidus in 59 (41%), and nephrogenicdiabetes insipidus in 3 (2%). Overall, among the 141 patients included in theanalysis, the indirect water-deprivation test determined the correct diagnosisin 108 patients (diagnostic accuracy, 76.6%; 95% confidence interval [CI], 68.9to 83.2), and the hypertonic saline infusion test (with a copeptin cutoff levelof >4.9 pmol per liter) determined the correct diagnosis in 136 patients(96.5%; 95% CI, 92.1 to 98.6; P<0.001). The indirect water-deprivation testcorrectly distinguished primary polydipsia from partial central diabetesinsipidus in 77 of 105 patients (73.3%; 95% CI, 63.9 to 81.2), and the hypertonic saline infusion test distinguished be-tween the twoconditions in 99 of 104 patients (95.2%; 95% CI, 89.4 to 98.1; adjusted P<0.001). One serious adverse event (desmopressin-induced hyponatremia thatresulted in hospitalization) occurred during the water-deprivation test.

共有144名患者接受了两项检查。最终诊断为82例患者（57％）的原发性多饮，59例中心性尿崩症（41％）和肾性尿崩症3例（2％）。总体而言，在分析中包括的141名患者中，间接水剥夺试验确定了108名患者的正确诊断（诊断准确性，76.6％; 95％置信区间[CI]，68.9至83.2）和高渗盐水输注试验（copeptin截断水平> 4.9 pmol / L）确定136名患者的正确诊断（96.5％; 95％CI，92.1至98.6; P <0.001）。间接缺水试验正确区分105例患者中77例（73.3％; 95％CI，63.9~81.2）的原发性多饮和部分中枢性尿崩症，高渗盐水输注试验在104例中的99例中区分患者（95.2％; 95％CI，89.4至98.1;调整后的P <0.001）。在缺水试验期间发生了一种严重的不良事件（去氨加压素诱导的低钠血症，导致住院治疗）。

CONCLUSIONS

The direct measurement of hypertonic saline–stimulatedplasma copeptin had greater diagnostic accuracy than the water-deprivation testin patients with hypotonic polyuria. (Funded by the Swiss National Foundationand others; ClinicalTrials.gov number, NCT01940614.)

高渗盐水刺激的血浆和肽素的直接测量比低渗多尿患者的水剥夺试验具有更高的诊断准确性。 （由瑞士国家基金会和其他人资助;ClinicalTrials.gov编号，NCT01940614。）

论文正文

The determination of a specific diagnosis in patients withpolyuria and low plasma osmolality (i.e., hypotonic polyuria) is a frequentproblem in clinical practice. In the absence of osmotic diuresis, polyuria canresult from one of three fundamentally different conditions1: insufficientproduction and secretion of the antidiuretic hormone arginine vasopressin(central diabetes insipidus), diminished renal sensitivity to the antidiureticactivity of arginine vasopressin (nephrogenic diabetes insipidus), or primaryexcessive fluid intake (primary polydipsia).

在多尿和低血浆渗透压（即低渗性多尿）患者中确定特定诊断是临床实践中的常见问题。 在没有渗透性利尿的情况下，多尿可以由三种根本不同的病症之一引起：抗利尿激素精氨酸加压素（中枢性尿崩症）的产生和分泌不足，肾脏对精氨酸加压素（肾性尿崩症）的抗利尿活性的敏感性降低，或原发性多余的液体摄入量（原发性多饮）。

It is important to differentiate these entities becausetreatments differ substantially, and incorrect strategies may lead to severecomplications. The indirect water-deprivation test measures the maximal urineconcentration during prolonged withholding of oral liquids and the renalresponse to administered desmopressin. It is conceptually simple, butdifficulties in interpretation are common, mainly because any water diuresismay compromise the renal medullary concentration gradient and promote adownregulation of kidney aquaporin-2 water channels, which could potentiallyaffect the diagnostic value of these urinary measures. Previous attempts toimprove the diagnosis of polyuric disorders with direct measurement ofcirculating arginine vasopressin failed to gain traction in clinical practice,largely because of the technical difficulties of measuring arginine vasopressin.

区分这些实体很重要，因为治疗方法存在很大差异，不正确的策略可能会导致严重的并发症。 间接禁水测试测量在长期停留口服液体期间的最大尿液浓度和对施用的去氨加压素的肾脏反应。它在概念上很简单，但解释上的困难是常见的，主要是因为任何水利尿都可能损害肾髓质浓度梯度并促进肾水通道蛋白-2水通道的下调，这可能潜在地影响这些排尿措施的诊断价值。先前通过直接测量循环精氨酸加压素来改善多尿症的诊断的尝试未能在临床实践中获得牵引力，主要是因为测量精氨酸加压素的技术困难。

Copeptin, the C-terminal segment of the arginine vasopressinprohormone, is an arginine vasopressin surrogate with high ex-vivo stabilitythat is easy to measure. In previous studies, we reported outcome data thatsuggested that measurement of osmotically stimulated copeptin might be usefulin differentiating the various causes of hypotonic polyuria. The current studyassessed the diagnostic performance of a test measuring copeptin that wasosmotically stimulated by water deprivation or by hypertonic saline infusion ascompared with the indirect water-deprivation test.

Copeptin是精氨酸加压素激素原的C末端片段，是精氨酸加压素替代物，具有高离体稳定性，易于测量。 在先前的研究中，我们报告的结果数据表明，渗透刺激的和肽素的测量可能有助于区分低渗多尿的各种原因。本研究评估了与间接缺水试验相比，通过水剥夺或高渗盐水输注渗透刺激的和肽素测试的诊断性能。

Study Design and Patients

This international, multicenter, prospective study wasconducted at 11 tertiary medical centers in Switzerland, Germany, and Brazilfrom July 2013 to June 2017; the 3-month follow-up visits were completed bySeptember 2017. We recruited 156 patients 16 years of age or older withhypotonic polyuria (a urine output of >50 ml per kilogram of body weightduring a 24-hour period, with a urine osmolality <800 mOsm per kilogram) orwith a confirmed diagnosis of central diabetes insipidus. Three patients wereexcluded from the analyses because they were found to have nephrogenic diabetesinsipidus, and 12 patients were excluded for other reasons (Fig. S1 in theSupplementary Appendix, available with the full text of this article atNEJM.org).

这项国际性，多中心，前瞻性研究于2013年7月至2017年6月在瑞士，德国和巴西的11个三级医疗中心进行;我们在2017年9月完成了为期3个月的随访。我们招募了156名16岁或以上的低渗性多尿患者（24小时内每公斤体重尿量> 50 ml，尿液渗透压<800 mOsm / kg）或确诊为中枢性尿崩症。3名患者被排除在分析之外，因为他们被发现患有肾性尿崩症，并且有12名患者因其他原因被排除在外（补充附录中的图S1，可在NEJM.org上获得本文全文）。

The local ethics committees at all centers approved thestudy protocol (available at NEJM.org). Written informed consent was obtainedfrom all patients or from a legal guardian, when applicable. Laboratorymeasurement of copeptin was funded by Thermo Fisher Scientific, which had noother role in the study; there was no other commercial support for the study.All the authors vouch for the accuracy and completeness of the data and for thefidelity of the study to the protocol.

所有中心的当地伦理委员会都批准了研究方案（可在NEJM.org上获得）。 在适用的情况下，从所有患者或法定监护人处获得书面知情同意书。 合成肽的实验室测量由赛默飞世尔科技公司资助，该研究在该研究中没有其他作用;这项研究没有其他商业支持。 所有作者都保证数据的准确性和完整性以及研究对协议的保真度。

The water-deprivation and hypertonic saline in-fusion testswere performed on separate days. After a detailed medical history was obtained,a standardized clinical and biochemical evaluation was performed. Magnetic resonance imaging (MRI) of the headwas performed at the discretion of the attending physician, although it wasrecommended in all patients if imaging had not been performed within 3 monthsbefore study enrollment. Diuretic or antidiuretic medications were discontinuedfor at least 24 hours before each test, and smoking and alcohol were prohibitedfor at least 12 hours before each test.

在不同的日子进行除水和高渗盐水融合试验。 在获得详细的病史后，进行标准化的临床和生化评估。头部的磁共振成像（MRI）由主治医师决定，尽管如果在研究登记前3个月内未进行成像，则建议所有患者使用。 在每次测试前至少24小时停用利尿剂或抗利尿药物，并且在每次测试前禁止吸烟和饮酒至少12小时。

Test protocols

Indirect water-deprivation test

As is standard for the water-deprivation test, a 17-hourfluid restriction started at midnight, or at 6 a.m. in patients with known orsuspected complete diabetes insipidus. Every 2 hours, vital signs and bodyweight were monitored, and urine was collected for measurement of volume andosmolality. Blood samples were obtained at 8 a.m. and immediately before the administrationof desmopressin (1 hour before the end of the test).

作为禁水测试的标准方法，对于已知或疑似完全性尿崩症的患者，在午夜或早上6点开始进行17小时的液体限制。 每2小时监测生命体征和体重，收集尿液用于测量体积和重量摩尔渗透压浓度。在上午8点和即将施用去氨加压素之前（测试结束前1小时）获得血液样品。

For safety reasons, the water-deprivation test was stoppedearly in patients who met one of the following criteria: a decrease in bodyweight of more than 3%, symptoms of orthostatic hypotension with an increase inheart rate or a decrease in mean arterial blood pressure of more than 15%, oran increase in plasma sodium level of 150 mmol or more per liter. At 4 p.m., orwhen the test was stopped, each patient received 2 μg of desmopressinintravenously, and a final urine specimen for osmolality measurement wasobtained at least 60 minutes thereafter.

出于安全原因，符合下列标准之一的患者早期停止缺水试验：体重下降超过3％，体位性低血压症状随着心率增加或平均值下降 动脉血压超过15％，或血浆钠水平升高150mmol或更高。 在下午4点，或当测试停止时，每个患者静脉内接受2μg去氨加压素，并且此后至少60分钟获得用于重量摩尔渗透压浓度测量的最终尿样。

Hypertonic SalineInfusion Test

Patients underwent the hypertonic saline infusion testbetween 8 a.m. and 11 a.m., as describedpreviously. An initial 250-ml bolus infusion of 3% saline was administered, andthe infusion was continued at a rate of 0.15 ml per kilogram per minute. Bloodsamples for the measurement of plasma osmolality and sodium, urea, and glucoselevels were obtained every 30 minutes, and sodium levels were monitored byvenous blood gas analysis until the target level of at least 150 mmol per literwas reached. Thereafter, a final blood sample for plasma copeptin measurementwas obtained, and patients were given water orally (30 ml of water perkilogram) within 30 minutes, followed by a 500-ml infusion of 5% glucose within40 to 60 minutes after the patients received water. For safety reasons, the plasma sodium levelwas measured again 1 hour after the start of the glucose infusion to ensurethat the level was within the normal range before the patient was discharged.

高渗盐水输注试验

如前所述，患者在上午8点至上午11点之间进行高渗盐水输注试验。最初250ml推注输注3％盐水，并以每公斤每分钟0.15ml的速度继续输注。每30分钟获得用于测量血浆渗透压和钠，尿素和葡萄糖水平的血液样品，并通过静脉血气分析监测钠水平，直至达到至少150mmol /L的目标水平。此后，获得用于血浆和肽素测量的最终血样，并且患者在30分钟内口服水（每公斤30ml水），然后在患者后40至60分钟内输注500ml的5％葡萄糖。出于安全原因，在葡萄糖输注开始后1小时再次测量血浆钠水平，以确保在患者出院前水平在正常范围内。

Adverse Events and Symptom Burden

Adverse events during both tests were strictly documented,and clinical symptoms were rated by patients according to a visual-analoguescale that ranged from 0 to 10, with 0 indicating no symptoms and 10 indicatingthe most severe symptoms imaginable. Additionaldetails are provided in the Supplementary Appendix.

不良事件和症状负担

严格记录两个测试期间的不良事件，并且患者根据视觉模拟量表评定临床症状，范围从0到10，其中0表示没有症状，10表示可以想象的最严重的症状。 补充附录中提供了其他详细信息。

Test Interpretation and Preliminary Diagnosis

After the patients had completed both tests, they weredischarged from the hospital with a preliminary diagnosis and treatmentrecommendation that were based on best current clinical practice. A follow-upvisit was scheduled for 3 months later to assess response to treatment andclinical outcome and to reevaluate the accuracy of the preliminary diagnosis.

测试解释和初步诊断

在患者完成两项测试后，他们从医院出院，并根据最新的临床实践进行初步诊断和治疗建议。计划在3个月后进行随访，以评估对治疗和临床结果的反应，并重新评估初步诊断的准确性。

Diagnostic Criteria

Indirect Water-Deprivation Test

In accordance with the original description of the indirectwater-deprivation test and the subsequent modification, complete centraldiabetes insipidus was diagnosed in patients who had a maximum urine osmolalityof less than 300 mOsm per kilogram and an increase in urine osmolality of morethan 50% after administration of desmopressin. Partial central diabetesinsipidus was diagnosed in patients who had a maximum urine osmolality of 300to 800 mOsm per kilogram and an increase in urine osmolality of 9 to 50% afteradministration of desmopressin. Primary polydipsia was diagnosed in patientswho had a maximum urine osmolality of 300 to 800 mOsm per kilogram and an increasein urine osmolality of less than 9% after administration of desmopressin.

诊断标准

间接缺水测试

根据间接剥夺水试验和随后修改的原始描述，在最大尿渗透压低于300mOsm / kg并且尿渗透压增加超过50％的患者中诊断出完全中枢性尿崩症,给予去氨加压素后。最大尿渗透压为300至800mOsm / kg且在给予去氨加压素后，尿渗透压增加9至50％的患者中诊断出部分中枢性尿崩症。在给予去氨加压素后，最大尿渗透压为300至800mOsm / kg且尿渗透压增加小于9％的患者中诊断出原发性烦渴。

Plasma Copeptin Stimulated by Water Deprivation

Previous data suggested that the diagnosticaccuracy of the indirect water-deprivation test could be improved by theadditional measurement of baseline (at 8 a.m.) as well as stimulated (beforeadministration of desmopressin) plasma copeptin levels. According to thoseresults, prespecified cutoff levels were used: a ratio of stimulated copeptin(the change in copeptin level over 8 hours during water deprivation, inpicomoles per liter) to plasma sodium (measured at the end of the test inmillimoles per liter) of 0.02 pmol or more per liter indicated primarypolydipsia, and a basal plasma copeptin level of less than 2.6 pmol per literindicated complete central diabetes insipidus. A ratio of less than 0.02 pmolper liter indicated partial central diabetes insipidus.

水剥夺刺激血浆和肽素

先前的数据表明间接水剥夺试验的诊断准确性可以通过额外测量基线（上午8点）以及刺激（施用去氨加压素前）血浆和肽素水平来改善。根据这些结果，使用预定的截止水平：刺激的和肽素的比例（在剥夺水中8小时内和肽素水平的变化，以每升皮摩尔为单位）与血浆钠（在试验结束时测量，以毫摩尔/升为单位）每升0.02pmol或更多表明原发性烦渴，并且基础血浆和肽素水平低于2.6pmol /升表明完全中枢性尿崩症。每升小于0.02pmol的比率表明部分中枢性尿崩症。

Plasma CopeptinStimulated by Hypertonic Saline Infusion

The diagnostic criteriafor hypertonic saline– stimulated copeptin in distinguishing primary polydipsiafrom central diabetes insipidus were suggested previously by our group and wereused in this study. A plasma copeptin cutoff level of 4.9 pmol or less perliter indicated complete or partial central diabetes insipidus, and a levelgreater than 4.9 pmol per liter indicated primary polydipsia.

高渗盐水灌注刺激血浆和肽素

高血压盐水刺激的和肽素区分原发性多饮症和中枢性尿崩症的诊断标准以前由我们小组提出并用于本研究。血浆和肽素截止水平为每升4.9pmol或更低表明完全或部分中枢性尿崩症，并且每升大于4.9pmol的水平表明原发性烦渴。

Final Reference Diagnosis

In the absence of adiagnostic standard, the final reference diagnosis was determined after thestudy was completed by two independent boardcertified experts in endocrinology,who were unaware of the copeptin levels, after careful consideration of eachpatient’s medical history and clinical symptoms, the results of the water-deprivation test, the available laboratory and imaging data, and thetherapeutic response at the 3-month follow-up. In the event of discordantdiagnoses (which occurred in 4 of 144 patients), a third expert was consulted,and results were discussed until a consensus was reached.

最终参考诊断

在缺乏诊断标准的情况下，在仔细考虑每位患者的病史和临床症状后，由两名独立的内分泌专家组成的完整的参考诊断确定最终参考诊断，他们不知道和肽素水平，在3个月的随访中，水剥夺试验的结果，可用的实验室和成像数据以及治疗反应。 如果出现不一致的诊断（144例患者中有4例发生），则咨询第三位专家，讨论结果直至达成共识。

Laboratory Measurements

Blood samples wereobtained and processed for measurement of plasma copeptin and for routinelaboratory measurements (urine and plasma osmolality, hematocrit, and plasmasodium, potassium, creatinine, urea, calcium, albumin, glucose, and hemoglobinlevels). Plasma copeptin was measured centrally in one batch with the use of acommercial automated immunofluorescence assay (B.R.A.H.M.S KRYPTOR CopeptinproAVP, Thermo Scientific Biomarkers). Details are provided in theSupplementary Appendix.

实验室测量

获得血液样品并进行处理以测量血浆和肽素并用于常规实验室测量（尿液和血浆渗透压，血细胞比容和血浆钠，钾，肌酸酐，尿素，钙，白蛋白，葡萄糖和血红蛋白水平）。使用商业自动化免疫荧光测定法（B.R.A.H.M.S KRYPTOR Copeptin proAVP，ThermoScientific Biomarkers）在一批中集中测量血浆和肽素。 详情见补充附录。

Statistical Analysis

The primary end point wasthe overall diagnostic accuracy — the percentage of correctly diagnosedpatients — in the differentiation of central diabetes insipidus from primarypolydipsia. Only patients with a final diagnosis were included in the analysis;however, the three patients with nephrogenic diabetes insipidus were onlydescriptively assessed. Details concerning the fullanalysis population and theper-protocol population, as well as additional statistical details, areprovided in the Supplementary Appendix.

主要终点是中枢性尿崩症与原发性多饮症的鉴别诊断准确性 - 正确诊断患者的百分比。只有最终诊断的患者才被纳入分析;然而，仅对3例肾性尿崩症患者进行了描述性评估。有关全面分析人口和每个议定书人口的详细信息以及其他统计细节见补充附录。

The primary objectiveswere first to determine whether the measurement of copeptin during hypertonicsaline infusion and during water deprivation was superior to the indirect waterdeprivation test, and then to determine whether copeptin measurement duringhypertonic saline infusion was noninferior to copeptin measurement during waterdeprivation; the second objective would be tested only if superiority could beshown for the first objective. The primary hypothesis thus consisted of twocomponents, with a two-step statistical testing procedure. Sample size was estimated for the noninferiority test: assuming a diagnostic accuracy of 90%for water deprivation–stimulated copeptin and a noninferiority margin of 10%, atotal of 115 patients who could be evaluated would provide 90% power toestablish the noninferiority of hypertonic saline–stimulated copeptin measurement to water-deprivation–stimulated copeptin measurement. To assesswhether the diagnostic accuracy varied depending on the severity of centraldiabetes insipidus, a prespecified subgroup analysis was performed to assessthe diagnostic accuracy of hypertonic saline–stimulated copeptin andwater-deprivation–stimulated copeptin as compared with the indirectwater-deprivation test in specifically distinguishing primary polydipsia frompartial central diabetes insipidus.

主要目的是首先确定高渗盐水输注期间和水剥夺期间的和肽素的测量是否优于间接水驱除测试，然后确定高渗盐水输注期间的和肽素测量是否不劣于水剥夺期间的和肽素测量;只有在第一个目标可以表现出优势时才会测试第二个目标。因此，主要假设由两部分组成，具有两步统计测试程序。估计非劣效性测试的样本量：假设水剥夺刺激的和肽素的诊断准确度为90％，非劣效率为10％，总共115名可以评估的患者将提供90％的能力来确定高渗的非劣效性盐水刺激的和肽素测量对水剥夺刺激的和肽素测量。为了评估诊断准确性是否根据中枢性尿崩症的严重程度而变化，进行预先指定的亚组分析以评估高渗盐水刺激的和肽素和水剥夺刺激的和肽素的诊断准确性，与间接水剥夺试验相比较。特别区分原发性多饮和部分中枢性尿崩症。

Baseline Characteristics

Of the 141 patients (66