Morganti A, Pelizzola D, Mantero F, Gazzano G, Opocher G, Piffanelli A
Centro Fisiologia Clinica e Ipertensione, Milan, Italy.
J Hypertens. 1995 Jan;13(1):19-26.
The measurement of plasma renin activity (PRA) is very convenient for estimating the action of the renin system, but its interlaboratory reproducibility is notoriously poor. This multicentre study aimed to examine whether an immunoradiometric assay which quantifies renin directly with monoclonal antibodies can reduce this limitation of the enzymatic assay. The study also aimed to establish the reference values of immunoreactive renin (IrR) in a large sample of normotensive subjects and patients with various pathophysiological conditions.
PRA and IrR were measured once in each of the eight participant centres in eight pool plasma samples with a wide range of renin content; in seven centres these measurements were repeated twice more in order to compare the intralaboratory interassay reproducibility of both methods. Finally, PRA and IrR were measured in the supine and standing positions in 503 subjects including normal controls, patients with various forms of hypertension, patients with Cushing's and Bartter's syndromes, patients with hepatic cirrhosis and pregnant women.
We found that both the inter- and intralaboratory coefficients of variation for PRA measurements were higher than those for IrR. In plasma samples from normal subjects and from patients, mean +/- SEM supine PRA and IrR ranged, respectively, from 0.08 +/- 0.03 ng/ml per h and 2.6 +/- 0.5 pg/ml in patients with Conn's syndrome to 7.2 +/- 2.5 ng/ml per h and 138 +/- 51 pg/ml in patients with hepatic cirrhosis. PRA and IrR were found to be significantly correlated in all laboratories (mean +/- SEM of correlation coefficients 0.84 +/- 0.03) and for all of the conditions (correlation coefficient ranging from 0.98 in patients with Cushing's syndrome to 0.50 in pregnant women). However, for the pregnant women the slope of the regression line depicting the PRA-IrR relationship was significantly steeper than for all of the other conditions.
In our experience the inter- and intralaboratory reproducibilities of the immunoradiometric assay appear to be greater than can be achieved with the enzymatic assay, the difference being probably due to the greater complexity of the latter. The two methods provide superimposable information on the renin-angiotensin system activity, except in pregnancy, during which the PRA:IrR ratio is much higher than in the other conditions. Therefore, in this and other pathophysiological situations associated with marked angiotensinogen concentration alterations, the enzymatic assay may be still preferable for assessing the activity of the system accurately.
血浆肾素活性（PRA）的测定对于评估肾素系统的作用非常方便，但其实验室间的可重复性很差。这项多中心研究旨在检验一种用单克隆抗体直接定量肾素的免疫放射分析方法是否能减少酶法分析的这一局限性。该研究还旨在确定大量血压正常的受试者以及患有各种病理生理状况的患者中免疫反应性肾素（IrR）的参考值。
在八个参与中心对八个肾素含量范围广泛的混合血浆样本各进行一次PRA和IrR测定；在七个中心对这些测定再重复两次，以比较两种方法在实验室内的批间可重复性。最后，对503名受试者（包括正常对照组、各种类型高血压患者、库欣综合征和巴特综合征患者、肝硬化患者及孕妇）进行仰卧位和站立位的PRA和IrR测定。
我们发现PRA测定的实验室间和实验室内变异系数均高于IrR。在正常受试者和患者的血浆样本中，仰卧位PRA和IrR的平均值±标准误范围分别为：原发性醛固酮增多症患者中为0.08±0.03 ng/ml·h和2.6±0.5 pg/ml，至肝硬化患者中为7.2±2.5 ng/ml·h和138±51 pg/ml。在所有实验室（相关系数平均值±标准误为0.84±0.03）以及所有状况下（相关系数范围从库欣综合征患者中的0.98至孕妇中的0.50），PRA和IrR均显著相关。然而，对于孕妇，描绘PRA-IrR关系的回归线斜率比所有其他状况下的斜率显著更陡。
根据我们的经验，免疫放射分析的实验室间和实验室内可重复性似乎高于酶法分析所能达到的水平，差异可能是由于后者更为复杂。这两种方法在肾素-血管紧张素系统活性方面提供了可叠加的信息，但在孕期除外，孕期PRA:IrR比值远高于其他状况。因此，在这种以及其他与血管紧张素原浓度显著改变相关的病理生理情况下，酶法分析可能仍更适合准确评估该系统活性。
