Open AccessA liquid chromatography tandem mass spectrometry assay for plasma renin activity using online solid-phase extraction
Author(s) -
S. Carter,
Laura Owen,
Michael Kerstens,
Robin P. F. Dullaart,
Brian Keevil
Publication year - 2012
Publication title -
annals of clinical biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.6
H-Index - 80
eISSN - 1758-1001
pISSN - 0004-5632
DOI - 10.1258/acb.2012.011186
Subject(s) - chromatography , chemistry , renin–angiotensin system , liquid chromatography–mass spectrometry , plasma renin activity , solid phase extraction , radioimmunoassay , primary aldosteronism , tandem mass spectrometry , mass spectrometry , ammonium hydroxide , detection limit , aldosterone , medicine , biochemistry , blood pressure , organic chemistry
Background 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).Methods 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).Results 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.Conclusions 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.