Plasma and urine aldosterone to plasma renin activity ratio in the diagnosis of primary aldosteronism.
OBJECTIVE
To establish the best cut-off value of the aldosterone (ALD)/plasma renin activity (PRA) ratio when screening patients for primary aldosteronism. One hundred and six patients with primary aldosteronism and 100 essential hypertensive patients were investigated in rigorous standardized conditions.


METHODS
The ALD/PRA cut-off values were calculated from both the plasma and urine ALD/PRA ratio and analyzed by receiver operating characteristic (ROC) curve. In patients with PRA below 0.2 ng/ml/h [our radioimmunoassay detection limit], values were calculated both with PRA levels set at 0.2 ng/ml/h ('adjusted') and with PRA levels detected ('unadjusted') in the assay.


RESULTS
ROC analysis on the ALD/PRA ratio indicated that the best performance was obtained when the plasma ALD (ng/dl)/PRA ratio was used in comparison with that observed in the urine ALD (microg/day)/PRA ratio. In patients with primary aldosteronism, as a whole group, the cut-off value of 69 corresponded to the best compromise value between sensitivity (96%) and specificity (85%), with and without PRA adjustment. In patients with aldosterone-producing adenoma, the cut-off to obtain 100% sensitivity with high specificity (85%) proved to be 69, with and without PRA adjustment. In patients with bilateral adrenal hyperplasia, both with and without PRA adjustment, the best compromise between sensitivity (94%) and specificity (86%) was a cut-off value of 71.


CONCLUSIONS
The best cut-off to identify patients with primary aldosteronism, corresponding to 69, was obtained by using the plasma ALD/PRA ratio. Adjustment of PRA to 0.2 ng/ml/h does not interfere with calculation of the plasma ALD/PRA ratio cut-off.
Bernini
Giampaolo
G
Department of Internal Medicine, University of Pisa, Via Roma 67, 56100 Pisa, Italy. g.bernini@med.unipi.it
Moretti
Angelica
A
Orlandini
Cinzia
C
Berti
Piero
P
Miccoli
Paolo
P
Bardini
Michele
M
Taurino
Chiara
C
Bernini
Matteo
M
Salvetti
Antonio
A
D000450:Aldosterone / Q000097:blood* / Q000652:urine*; D005260:Female; D006801:Humans; D006929:Hyperaldosteronism / Q000175:diagnosis*; D006973:Hypertension / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D012016:Reference Values; D012083:Renin / Q000097:blood*; D012189:Retrospective Studies
D000450:Aldosterone; D012083:Renin