The diagnostic utility of the captopril challenge test for primary aldosteronism in a Bangladeshi population: a prospective study.

Abstract

Primary aldosteronism (PA) is the most common cause of endocrine hypertension. Current screening uses the plasma aldosterone-to-renin ratio (ARR) followed by confirmatory testing with one of several tests. The saline suppression test (SST) is widely used but contraindicated in patients with renal insufficiency or congestive heart failure. The captopril challenge test (CCT) offers a safe, inexpensive and convenient alternative to the SST, but diagnostic thresholds and reported accuracy vary between centres. Furthermore, none of the previous comparative studies have been carried out in low- and middle-income countries, where the affordability of the CCT may offer distinct advantages. This study aimed to evaluate the diagnostic accuracy of the CCT compared to the SST in a Bangladeshi population. In this prospective study, consecutive hypertensive patients with an ARR >50 ​pmol/mIU underwent both the SST and CCT. Using the SST as the reference standard, where plasma aldosterone concentration (PAC) post SST ≥170 ​pmol/L is considered diagnostic of PA, the area under the receiver operating characteristic curve (AUC), sensitivity, specificity, and negative and positive predictive values of different diagnostic criteria for the CCT were calculated. A total of 103 patients completed both confirmatory tests. The diagnostic accuracy of the post-captopril PAC at both 1 ​h and 2 ​h outperformed post-captopril ARR or the percentage suppression of PAC (AUC 0.77, 0.70 and 0.56, respectively; p<0.001). PACs >333 ​pmol/L at 1 ​h and 2 ​h post administration of captopril demonstrated sensitivities of 54.5% and 44.4%, with specificities of 91.5% and 93.6%, respectively. A post-captopril PAC <151 ​pmol/L effectively ruled out PA with 96.4% sensitivity, while a PAC >380 ​pmol/L ruled in the diagnosis of PA with 95.7% specificity. Overall, our findings indicate that the CCT, based on post-captopril PAC, achieves comparable diagnostic accuracy to the seated SST. The diagnostic performance was similar at either 1 ​h or 2 ​h post administration of captopril, suggesting that 1 ​h may be preferred in a CCT protocol for efficiency. The CCT represents a safe and convenient confirmatory test to guide decisions on PA subtyping or medical treatment, especially in resource-limited settings.