From the Guidelines
The next step in diagnosing this 27-year-old woman with hypertension, hypokalemia, and metabolic alkalosis should be measuring plasma aldosterone and renin levels, as this combination of findings strongly suggests primary hyperaldosteronism (Conn's syndrome) or secondary causes of mineralocorticoid excess. This diagnostic approach is supported by the most recent and highest quality study, which recommends measuring plasma aldosterone and renin activity to assess for primary aldosteronism 1. The patient's presentation of hypertension, hypokalemia, and metabolic alkalosis is consistent with primary hyperaldosteronism, and measuring the aldosterone-to-renin ratio is a useful screening test for this condition.
Before testing, the patient should discontinue medications that affect the renin-angiotensin-aldosterone system, including diuretics, ACE inhibitors, ARBs, and beta-blockers for at least 2 weeks if possible. The test should be performed in the morning with the patient seated, and blood samples should be collected simultaneously. An elevated aldosterone-to-renin ratio (typically >30 ng/dL per ng/mL/hr) with an absolute aldosterone level >15 ng/dL suggests primary hyperaldosteronism. If positive, confirmatory tests like a saline suppression test would follow. Additional workup may include 24-hour urinary free cortisol to rule out Cushing's syndrome, urinary metanephrines to exclude pheochromocytoma, and renal artery imaging if renovascular hypertension is suspected.
Key points to consider in the diagnosis and management of primary hyperaldosteronism include:
- Measuring plasma aldosterone and renin activity to assess for primary aldosteronism 1
- Discontinuing medications that affect the renin-angiotensin-aldosterone system before testing
- Performing confirmatory tests like a saline suppression test if the aldosterone-to-renin ratio is elevated
- Considering additional workup to rule out other causes of hypertension and hypokalemia
- Guiding treatment based on the specific cause of primary hyperaldosteronism, whether it's surgical removal of an aldosterone-producing adenoma or targeted medical therapy.
The most recent study 1 provides the best evidence for the diagnostic approach, and its recommendations should be followed in this case. The other studies 1 provide additional context and support for the diagnostic approach, but the most recent study takes precedence.
From the Research
Diagnosis of Primary Aldosteronism
The patient's symptoms of hypertension, hypokalemia, and metabolic alkalosis suggest primary aldosteronism. The next step in diagnosis is to confirm the presence of autonomous aldosterone production.
- The aldosterone-to-renin ratio (ARR) is a key step for early detection of primary aldosteronism 2.
- A high ARR suggests primary aldosteronism, which can be caused by an aldosterone-producing adenoma or bilateral adrenal hyperplasia 3, 4.
- The diagnosis of primary aldosteronism should be suspected when spontaneous hypokalemia or easily provoked hypokalemia is found in a patient with hypertension 4.
- The Expanding Spectrum of Primary Aldosteronism suggests that primary aldosteronism manifests across a wide spectrum of severity, ranging from mild to overt, that correlates with cardiovascular risk 5.
Diagnostic Tests
The following diagnostic tests can be used to confirm the diagnosis of primary aldosteronism:
- Measurement of plasma aldosterone and renin concentrations to calculate the ARR 2, 6.
- A 24-hour urine collection for measurement of cortisol concentration may not be necessary as an initial step, but can be used to confirm the diagnosis of primary aldosteronism 3.
- Echocardiography and renal artery duplex scan may not be directly relevant to the diagnosis of primary aldosteronism, but can be used to evaluate the effects of hypertension on the heart and kidneys.
Next Step
Based on the patient's symptoms and laboratory results, the most appropriate next step in diagnosis is to measure the serum aldosterone:renin ratio (ARR) to confirm the presence of autonomous aldosterone production.
- The correct answer is D) Measurement of serum aldosterone:renin ratio.