Rapid screening test for primary hyperaldosteronism: ratio of plasma aldosterone to renin concentration determined by fully automated chemiluminescence immunoassays.

BACKGROUND

The ratio of plasma aldosterone concentration to plasma renin activity (PAC/PRA) is the most common screening test for primary hyperaldosteronism (PHA), but it is not standardized among laboratories. We evaluated new automated assays for the simultaneous measurement of PAC and plasma renin concentration (PRC).

METHODS

We studied 76 healthy normotensive volunteers and 28 patients with confirmed PHA. PAC and PRC were measured immunochemically in EDTA plasma on the Nichols Advantage chemiluminescence analyzer, and PRA was determined by an activity assay.

RESULTS

In volunteers, PAC varied from 33.3 to 1930 pmol/L, PRA from 1.13 to 19.7 ng.mL(-1).h(-1) (0.215 ng.mL(-1).h(-1) = 1 pmol.L(-1).s(-1)), and PRC from 5.70 to 116 mU/L. PAC/PRA ratios ranged from 4.35 to 494 (pmol/L)/(ng.mL(-1).h(-1)) and PAC/PRC ratios from 0.69 to 71.0 pmol/mU. In PHA patients, PAC ranged from 158 to 5012 pmol/L, PRA from 0.40 to 1.70 ng.mL(-1).h(-1), and PRC from 0.80 to 11.7 mU/L. PAC/PRA ratios were between 298 and 6756 (pmol/L)/(ng.mL(-1).h(-1)) and PAC/PRC ratios between 105 and 2328 pmol/mU. Whereas PAC or PRC showed broad overlap between PHA patients and volunteers, the PAC/PRC ratio indicated distinct discrimination of these two groups at a cutoff of 71 pmol/mU.

CONCLUSION

The PAC/PRC ratio offers several practical advantages compared with the PAC/PRA screening method. The present study offers preliminary evidence that it may be a useful screening test for PHA. Further studies are required to validate these results, especially in hypertensive cohorts.