Department of Clinical Biochemistry, University Hospital of South Manchester, Southmoor Road, Manchester M23 9LT, UK.
Ann Clin Biochem. 2012 Nov;49(Pt 6):570-9. doi: 10.1258/acb.2012.011186. Epub 2012 Sep 27.
The plasma renin activity (PRA) assay measures the ability of renin to generate angiotensin I (AngI) from angiotensinogen. It is used to monitor mineralocorticoid therapy and to screen hypertensive individuals for primary aldosteronism (PA).
Samples were incubated in the presence of protease inhibitors for 6.5 and 24 h. The reaction was stopped by the addition of 2% ammonium hydroxide. AngI was then quantified by liquid chromatography tandem mass spectrometry using online solid-phase extraction (XLC-MS/MS).
This method requires a sample volume of 50 μL and has an inter-assay precision <14% across the working range. A 6.5-h incubation gave a lower limit of quantification (LLOQ) of 0.3 nmol/L/h and this can be reduced to 0.08 nmol/L/h using a 24-h incubation. Comparison to a radioimmunoassay revealed excellent correlation (r(2) = 0.98), but a 37% negative bias. We also found that renin is stable in whole blood for up to 24 h at room temperature. In contrast, storage at 4°C should be avoided as prorenin cryoactivation can affect the PRA result in some patient groups.
We have developed and fully validated a semi-automated XLC-MS/MS method for the measurement of PRA. In addition, a reference range specific to this assay has been defined. We have also demonstrated that renin is stable for up to 24 h at room temperature. This will enable this assay to be extended to samples taken in primary care, potentially increasing the number of hypertensive patients who can be screened for PA.
血浆肾素活性（PRA）测定法可测量肾素将血管紧张素原转化为血管紧张素 I（AngI）的能力。它用于监测皮质激素治疗，并筛查原发性醛固酮增多症（PA）的高血压个体。
样品在存在蛋白酶抑制剂的情况下孵育 6.5 和 24 小时。通过加入 2％氨水溶液来终止反应。然后通过在线固相萃取（XLC-MS/MS）使用液相色谱串联质谱法定量 AngI。
该方法需要 50 μL 的样品量，在工作范围内的批内精密度<14％。6.5 小时孵育的定量下限（LLOQ）为 0.3 nmol/L/h，通过 24 小时孵育可将其降低至 0.08 nmol/L/h。与放射免疫测定法相比，相关性非常好（r²=0.98），但存在 37％的负偏倚。我们还发现，室温下全血中的肾素在长达 24 小时内稳定。相比之下，应避免在 4°C 下储存，因为前肾素的低温激活可能会影响某些患者群体的 PRA 结果。
我们已经开发并全面验证了一种用于测量 PRA 的半自动化 XLC-MS/MS 方法。此外，已经定义了特定于该测定法的参考范围。我们还证明，室温下肾素稳定长达 24 小时。这将使该测定法能够扩展到初级保健中采集的样本，从而可能增加可以筛查 PA 的高血压患者数量。
