From the Guidelines
Laboratory tests for secondary hypertension should include a comprehensive panel to identify underlying causes, with initial screening consisting of basic metabolic panel (BMP), complete blood count (CBC), urinalysis, and thyroid-stimulating hormone (TSH), as recommended by the 2024 ESC guidelines for the management of elevated blood pressure and hypertension 1.
Initial Screening Tests
- Basic metabolic panel (BMP) to assess kidney function and electrolytes
- Complete blood count (CBC)
- Urinalysis
- Thyroid-stimulating hormone (TSH)
Additional Tests Based on Clinical Suspicion
- For suspected primary aldosteronism: measure plasma aldosterone concentration and plasma renin activity, with an aldosterone-to-renin ratio >20-30 suggesting the condition
- Pheochromocytoma evaluation: 24-hour urine collection for metanephrines and catecholamines or plasma free metanephrines
- For Cushing's syndrome: 24-hour urinary free cortisol test or overnight dexamethasone suppression test
- Renal ultrasound to detect kidney abnormalities
- In younger patients, especially females, consider testing for fibromuscular dysplasia These tests should be ordered in a stepwise approach based on clinical suspicion, patient demographics, and presentation, as outlined in the 2020 International Society of Hypertension global hypertension practice guidelines 1 and the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults 1. Early identification of secondary causes is crucial as they may require specific treatments beyond standard antihypertensive therapy, potentially leading to cure rather than lifelong medication management.
From the Research
Laboratory Tests for Secondary Hypertension
The diagnosis of secondary hypertension involves a range of laboratory tests to identify the underlying cause. Some of the key tests include:
- Electrolytes, urea, and creatinine to assess renal function 2
- Aldosterone:renin ratio to screen for primary aldosteronism, which should be done before starting antihypertensive drugs if possible 2
- Urinalysis and urine albumin:creatinine ratio to evaluate kidney function and detect potential renal causes 2
- Tests to identify primary aldosteronism, such as confirmatory testing after an abnormal aldosterone:renin ratio 3
- Tests to diagnose renovascular hypertension, such as imaging studies or renal function tests 3
- Tests to diagnose pheochromocytoma, including genetic testing and biochemical assays 3
- Tests to diagnose rarer monogenic forms and other renal and endocrine causes of arterial hypertension 3
Selection of Patients for Testing
It is essential to select patients with a high pre-test probability of secondary forms of hypertension to undergo laboratory testing 3. This includes patients with:
- Early-onset or severe hypertension
- Resistant hypertension
- Suggestive family history or clinical clues pointing to a specific secondary cause
- History of renal disease, primary aldosteronism, or obstructive sleep apnoea
- Use of medicines, illicit substances, or alcohol that may contribute to hypertension 2