[Clinical evaluation of the renin-aldosterone system: comparison of two methods in different clinical conditions].

INTRODUCTION

Measurement of plasma aldosterone/renin ratio is the key step in the diagnosis of primary aldosteronism.

AIM: The aim of the authors was to analyze and compare the diagnostic utility of plasma aldosterone/renin activity and plasma aldosterone/renin concentration ratios.

METHODS

Plasma aldosterone and plasma renin activity were determined by radioimmunoassays and plasma renin concentration was measured by immunoradiometric assay in 134 subjects (80 women and 54 men, aged 46±15.5 years) including 49 healthy blood donors (control group), 59 patients with hypertension (25 treated and 34 untreated) and 26 patients with incidentally discovered adrenal adenomas.

RESULTS

There was a weak correlation (r = 0.59) between plasma renin activity and plasma renin concentration in the lower range (plasma renin activity, 0.63±0.41 ng/ml/h; plasma renin concentration, 8.1±4.9 ng/l). Considering the cut-off value of plasma aldosterone/renin ratios determined in controls (plasma aldosterone/renin activity ratio, 30 ng/dl/ng/ml/h; plasma aldosterone/renin concentration ratio, 3.0 ng/dl/ng/l), high proportion of falsely positive results were found among patients on beta-receptor blocker therapy (plasma aldosterone/renin activity ratio, 22.2%; plasma aldosterone/renin concentration ratio, 44.4%)

CONCLUSION

The widely used plasma aldosterone/renin activity ratio can only be replaced with plasma aldosterone/renin concentration ratio with precaution on different clinical conditions.