Primary aldosteronism: diagnostic accuracy of the losartan and captopril tests.
BACKGROUND
To assess whether angiotensin-II receptor blockers (ARBs) offer any additional advantage in confirming the diagnosis of primary aldosteronism (PA) and their use in the differentiation of PA subtypes.


METHODS
A prospective, cohort, head-to-head study was conducted between July 2003 and July 2006. A total of 135 patients received captopril and losartan tests to confirm the diagnosis of PA in the TAIPAI (Taiwan Primary Aldosteronism Investigation) intervention.


RESULTS
In total, 71 patients were diagnosed with PA. The area under the receiver-operating characteristic (ROC) curve of the postcaptopril plasma aldosterone concentration (PAC) was significantly less than that of the postlosartan PAC (0.744 vs. 0.829, P = 0.038). Using an aldosterone-renin ratio (ARR, ng/dl per ng/ml/h) >35 with a PAC >10 ng/dl, the specificity was 89.1% vs. 93.8% and the sensitivity was 66.2% vs. 84.5 % for the captopril test vs. the losartan test, respectively. With respect to the losartan test, the accuracy was 88.9%, the agreement was good (k = 0.778), and there was no disagreement with the McNemar test (P = 0.118). Losartan had the advantage of a better negative predictive value to exclude PA when patients were referred with a serum potassium (SK) level <3.8 mmol/l. When a postlosartan ARR >60 was the cutoff value, the positive predictive value was 82% with a negative predictive value of 57% in distinguishing aldosterone-producing adenomas (APAs) from idiopathic hyperaldosteronism (IHA).


CONCLUSIONS
The postlosartan ARR and PAC were shown to have better accuracy for the diagnosis of PA than the captopril test. With a postlosartan ARR >60, APAs can be adequately differentiated from IHA.
Wu
Vin-Cent
VC
Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
Chang
Hung-Wei
HW
Liu
Kao-Lang
KL
Lin
Yen-Hung
YH
Chueh
Shih-Chieh
SC
Lin
Wei-Chou
WC
Ho
Yi-Luwn
YL
Huang
Jeng-Wen
JW
Chiang
Chih-Kang
CK
Yang
Shao-Yu
SY
Chen
Yung-Ming
YM
Wang
Shuo-Meng
SM
Huang
Kuo-How
KH
Hsieh
Bor-Sen
BS
Wu
Kwan-Dun
KD
D000328:Adult; D047228:Angiotensin II Type 1 Receptor Blockers; D000806:Angiotensin-Converting Enzyme Inhibitors; D019540:Area Under Curve; D002216:Captopril; D015331:Cohort Studies; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D006929:Hyperaldosteronism / Q000145:classification / Q000175:diagnosis*; D019808:Losartan; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D013624:Taiwan; D014057:Tomography, X-Ray Computed
D047228:Angiotensin II Type 1 Receptor Blockers; D000806:Angiotensin-Converting Enzyme Inhibitors; D002216:Captopril; D019808:Losartan