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 aldosterone/renin (A/R) ratio in South African normotensives under typical outpatient conditions, and to estimate the prevalence of primary aldosteronism (PA) among hypertensives in primary care settings.


METHODS
One hundred and thirty-six normotensive subjects and 154 sex- and age-matched hypertensives at three primary care clinics had measurements of blood pressure, plasma creatinine, K+, aldosterone, plasma renin 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 Medication was not withdrawn before testing.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 normotensives (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) normotensives. In hypertensives, there were no significant differences in renin or aldosterone levels between the three population groups. Urinary Na+/creatinine ratios, an index of Na+ intake, were not significantly different in the three population groups. None of the normotensives had an A/R ratio > or = 1,000 plus aldosterone > or = 750, while 7.1% of hypertensives exceeded these levels, suggesting that they are appropriate criteria for screening for PA.


CONCLUSIONS
A large fraction of black normotensive subjects had low renin and aldosterone levels compared with whites, suggesting a salt-retaining tendency in black subjects. These results have important implications for the interpretation of plasma renin and aldosterone levels in hypertensive patients. In primary care settings, 7.1% of hypertensives had biochemical results indicating the need for investigation of PA.
Rayner
B L
BL
Hypertension Clinic, Groote Schuur Hospital and University of Cape Town.
Myers
J E
JE
Opie
L H
LH
Trinder
Y A
YA
Davidson
J S
JS
D000450:Aldosterone / Q000097:blood*; D005006:Ethnicity; D005260:Female; D006801:Humans; D006929:Hyperaldosteronism / Q000175:diagnosis* / Q000453:epidemiology*; D006973:Hypertension / Q000097:blood / Q000150:complications* / Q000188:drug therapy; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012016:Reference Values; D012083:Renin / Q000097:blood*; D012964:Sodium / Q000652:urine; D013019:South Africa / Q000453:epidemiology; D018709:Statistics, Nonparametric
D000450:Aldosterone; D012964:Sodium; D012083:Renin