Prospective evaluation of the saline infusion test for excluding primary aldosteronism due to aldosterone-producing adenoma.
BACKGROUND
Data on the performance of the tests used to confirm the diagnosis of primary aldosteronism (PA) are limited.


OBJECTIVE
To prospectively investigate the accuracy of the saline infusion test (SIT).


METHODS
Three hundred and seventeen (26.9%) out of 1125 patients screened in the PAPY study underwent measurement of plasma aldosterone, cortisol and renin activity after infusion of 2 l of isotonic saline intravenously over 4 h. They comprised patients with a baseline aldosterone/renin ratio (ARR) > 40 and one every four patients not fulfilling such criterion. The area under the receiver-operator characteristic curves (AUC) of aldosterone values after SIT was used as a measure of accuracy for diagnosing PA, aldosterone-producing adenoma (APA) or idiopathic hyperaldosteronism (IHA).


RESULTS
One hundred and twenty (37.9%) patients had PA that was due to an APA in 46 (38.3%) and to IHA in 74 (61.7%). No untoward effect occurred with the SIT. The AUC (0.811 +/- 0.026, 0.878 +/- 0.040 and 0.784 +/- 0.034 for identification of PA, APA and IHA, respectively) was higher (P < 0.0001) than that under the diagonal. By sensitivity/specificity versus criterion values plot, the best aldosterone cut-off values for identifying APA and IHA were 6.75 and 6.91 ng/dl, respectively. However, even at these optimal cut-offs, sensitivity and specificity were moderate because of values overlapping between patients with and without the disease. Moreover, there were no differences of AUC and aldosterone cut-offs between APA and IHA.


CONCLUSIONS
In a multicenter study the SIT was safe and specific for excluding PA, but had no place for discriminating between an APA and IHA.
Rossi
Gian Paolo
GP
DMCS-Clinica Medica 4, University Hospital, Padova, Italy. gianpaolo.rossi@unipd.it
Belfiore
Anna
A
Bernini
Giampaolo
G
Desideri
Giovambattista
G
Fabris
Bruno
B
Ferri
Claudio
C
Giacchetti
Gilberta
G
Letizia
Claudio
C
Maccario
Mauro
M
Mallamaci
Francesca
F
Mannelli
Massimo
M
Montemurro
Domenico
D
Palumbo
Gaetana
G
Rizzoni
Damiano
D
Rossi
Ermanno
E
Semplicini
Andrea
A
Agabiti-Rosei
Enrico
E
Pessina
Achille Cesare
AC
Mantero
Franco
F
D000236:Adenoma / Q000097:blood* / Q000473:pathology; D000310:Adrenal Gland Neoplasms / Q000097:blood* / Q000473:pathology; D000450:Aldosterone / Q000097:blood*; D003937:Diagnosis, Differential; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D006929:Hyperaldosteronism / Q000097:blood / Q000150:complications / Q000175:diagnosis*; D006973:Hypertension / Q000097:blood / Q000175:diagnosis / Q000209:etiology; D007262:Infusions, Intravenous; D008875:Middle Aged; D011446:Prospective Studies; D012372:ROC Curve; D012083:Renin / Q000097:blood; D015203:Reproducibility of Results; D012965:Sodium Chloride / Q000008:administration & dosage
D012965:Sodium Chloride; D000450:Aldosterone; D012083:Renin; D006854:Hydrocortisone