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Second test improves diagnostic accuracy for primary aldosteronism
A combination of the captopril challenge test and saline infusion test improves the diagnostic accuracy for primary aldosteronism when compared with a saline infusion test alone, according to findings published in Clinical Endocrinology.
Confirmation testing is a crucial step in the diagnosis of primary aldosteronism, Jinbo Hu, MD, PhD, a consultant in the department of endocrinology at the First Affiliated Hospital of Chongqing Medical University, China, and colleagues wrote; however, one of the most commonly used tests, the saline infusion test, often produces indeterminate results.
“Adults with indeterminate saline infusion test results should undergo the captopril challenge test to increase the likelihood of reaching a definitive diagnosis of primary aldosteronism,” Hu told Healio. “This suggestion might be supplementary to the current guidelines for the addition of an alternative diagnostic strategy to confirm the primary aldosteronism diagnosis in the setting of an indeterminate saline infusion test.”
There is little guidance on how to interpret inconclusive saline infusion test results or subsequent steps to confirm the diagnosis. To our knowledge, this is the first study to assess the diagnostic accuracy of a combination of the captopril challenge test and saline infusion test.”
Lin and colleagues analyzed data from 280 people with hypertension considered at high risk for primary aldosteronism according to Endocrine Society guidelines. Participants agreed to undergo three confirmatory tests: the saline infusion test, the captopril challenge test and the fludrocortisone suppression test (used as reference standard). For the saline infusion test, a post-infusion plasma aldosterone concentration of 10 ng/dL was considered probable primary aldosteronism; a post-infusion plasma aldosterone concentration of 11 ng/dL or greater was considered positive for the captopril challenge test. Using the fludrocortisone suppression test as reference, researchers calculated diagnostic parameters including area under the receiver-operator characteristic curves, sensitivity and specificity.
Within the cohort, 65 patients (23.2%) were diagnosed as indeterminate after the saline infusion test. With the addition of the captopril challenge test, true positive numbers increased from 134 to 147, and false negative numbers decreased from 27 to 14.
Compared with the saline infusion test alone, a combination of the saline infusion test plus captopril challenge test showed a higher AUC (0.91 vs. 0.87; P = .041) and an increased sensitivity for the diagnosis of primary aldosteronism (0.91 vs. 0.83; P = .028). Specificity did not change with the additional test, according to the researchers.
“Subjects with indeterminate saline infusion test results should undergo the captopril challenge test to increase the likelihood of reaching a definitive diagnosis that has ramifications for long-term cardiovascular risk management,” the researchers wrote. – by Regina Schaffer
For more information:
Jinbo Hu, MD, PhD, can be reached at the First Affiliated Hospital of Chongqing Medical University, No. 1 Youyi St., Yuzhong District, Chongqing, China, 400016; email: hujinbo_568@163.com.
Disclosures: The authors report no relevant financial disclosures.
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