Screening for primary aldosteronism - Normal ranges for aldosterone and renin in three South African population groups

Objective. To establish normal ranges for plasma aldosterone, renin and ald osterone/renin (A/R) ratio in South African normotensives under typical out patient conditions, and to estimate the prevalence of primary aldosteronism (PA) among hypertensives in primary care settings. Design and methods. One hundred and thirty-six normotensive subjects and 15 4 sex- and age-matched hypertensives at three primary care clinics had meas urements of blood pressure, plasma creatinine, K+, aldosterone, plasma reni n activity, and spot urine for urinary Na+/creatinine ratio. Medication was not withdrawn before testing. Results. Mean plasma renin activity in black normotensive subjects (0.95 +/ - 1.25 ng/ml/h, mean standard deviation (SD)) was significantly lower than in white (2.09 +/- 1.12 ng/ml/h; P < 0.0001) and Coloured (1.81 +/- 1.86 ng /ml/h, P = 0.013) normotensives. Mean plasma aldosterone in black normotens ives (306 +/- 147 pmol/l) was also significantly lower than in white (506 /- 324 pmol/l, P = 0.0002) and coloured (418 +/- 304 pmol/l, P = 0.0148) no rmotensives. In hypertensives, there were no significant differences in ren in or aldosterone levels between the three population groups. Urinary Na+/c reatinine ratios, an index of Na+ intake, were not significantly different in the three population groups. None of the normotensives had an A/R ratio greater than or equal to 1000 plus aldosterone greater than or equal to 750 , while 7.1% of hypertensives exceeded these levels, suggesting that they a re appropriate criteria for screening for PA.