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Aldosterone-Renin Ratio in Primary Hyperaldosteronism
Determining the ARR was enough to confirm or exclude diagnoses of primary aldosteronism in some, but not all, cases; it's probably best to make sure that patients are evaluated by experienced physicians.
The aldosterone-renin ratio (ARR) has gained popularity as a screening test for primary hyperaldosteronism, a probably underdiagnosed cause of hypertension. However, studies have yielded varying definitions of a positive test.
In this retrospective study from Hong Kong, researchers analyzed results from 62 patients referred to a hospital's endocrine unit with suspected primary hyperaldosteronism (usually because of hypertension plus hypokalemia). Final diagnoses were based on surgical pathology, saline suppression tests, computed tomography findings, and adrenal venous sampling (not all patients underwent all tests). ARRs were determined in each patient after overnight recumbency, after sitting for 30 minutes, and after 4 hours of ambulation.
Primary hyperaldosteronism ultimately was diagnosed in 45 patients; the other 17 were presumed to have essential hypertension. After reviewing all ARR results, the authors conclude that testing patients after 30 minutes seated is acceptable for screening. An ARR cutoff of 23.6 ng/dL per ng/mL · hour had a sensitivity of 97% and specificity of 94%. A cutoff of 66.9 yielded 100% specificity: All patients with levels above this cutoff had primary hyperaldosteronism. The median ARR was 136.4 among patients with hyperaldosteronism and 5.6 among controls.
Comment: In this study, an ARR >66.9 after 30 minutes seated confirmed primary hyperaldosteronism, whereas an ARR <23.6 excluded it with near certainty. Between these two cutoffs, additional tests were needed to confirm or exclude the diagnosis. Because of other important variables (e.g., performance of specific test kits, differing patient populations across studies), it's probably best to have patients evaluated by physicians with experience in diagnosing primary hyperaldosteronism.
— Allan S. Brett, MD
Published in Journal Watch General Medicine February 11, 2005
Citation(s):
Tiu S-C et al. The use of aldosterone-renin ratio as a diagnostic test for primary hyperaldosteronism and its test characteristics under different conditions of blood sampling. J Clin Endocrinol Metab 2005 Jan; 90:72-8.
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