A 40-year-old woman with treatment-resistant hypertension (BP 162/98 mmHg on amlodipine 10 mg + lisinopril 40 mg + chlorthalidone 25 mg) is evaluated. Aldosterone-to-renin ratio is 42 (ng/dL)/(ng/mL/h), with aldosterone 22 ng/dL and suppressed PRA <0.5 ng/mL/h. What is the next confirmatory test?
- A Salt loading test (oral or IV sodium loading with aldosterone suppression) ✓
- B CT adrenal glands
- C Dexamethasone suppression test
- D Adrenal venous sampling (AVS)
Correct answer: A. Salt loading test (oral or IV sodium loading with aldosterone suppression)
Explanation
An elevated ARR (>30 ng/dL per ng/mL/h) is a screening test for primary hyperaldosteronism requiring confirmatory testing before proceeding to imaging or AVS. The Endocrine Society 2016 guidelines recommend one of four confirmatory tests: oral sodium loading (24-hr urine aldosterone >12 μg/day), IV saline suppression test (4L normal saline over 4 hours; aldosterone >10 ng/dL confirms), fludrocortisone suppression test, or captopril challenge test. CT is performed only after biochemical confirmation to localise the lesion.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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