Laboratory Tests for Hypertension Evaluation
The essential laboratory tests for hypertension evaluation include blood tests for sodium, potassium, serum creatinine with eGFR, lipid profile, fasting glucose, complete blood count, thyroid-stimulating hormone, urinalysis, and a 12-lead ECG. 1
Basic Laboratory Tests (Required for All Hypertensive Patients)
Blood Tests
- Sodium and potassium: To identify electrolyte abnormalities that may suggest secondary causes of hypertension 1
- Serum creatinine with estimated glomerular filtration rate (eGFR): To assess kidney function and establish baseline renal status 1
- Lipid profile: To evaluate cardiovascular risk and guide management decisions 1
- Fasting blood glucose: To screen for diabetes or prediabetes, which frequently coexists with hypertension (present in 15-20% of hypertensive patients) 1, 2
- Complete blood count: To evaluate for anemia or other hematologic abnormalities 1, 2
- Thyroid-stimulating hormone: To screen for thyroid dysfunction as a potential secondary cause 1, 2
Urine Tests
- Urinalysis: To screen for kidney disease and detect hematuria 1
- Urinary albumin-to-creatinine ratio: More sensitive than dipstick urinalysis for detecting early kidney damage (recommended over urine dipstick) 1, 2
Cardiac Assessment
- 12-lead ECG: To detect atrial fibrillation, left ventricular hypertrophy, or ischemic heart disease 1
Optional Tests (Based on Clinical Indications)
Cardiovascular Assessment
- Echocardiography: For patients with uncontrolled hypertension, suspected hypertensive heart disease, or abnormal ECG findings 1
- Carotid ultrasound: To detect plaques or stenosis indicating atherosclerosis 1
- Ankle-brachial index: To evaluate for peripheral artery disease 1
Additional Laboratory Tests
- Serum uric acid: Common in hypertensive patients (25%) and may provide additional risk stratification 1, 2
- Liver function tests: Particularly in patients with metabolic syndrome or suspected fatty liver disease 1
Tests for Suspected Secondary Hypertension
- Aldosterone-renin ratio: When primary aldosteronism is suspected (hypokalemia, resistant hypertension) 1
- Plasma free metanephrines: When pheochromocytoma is suspected (episodic hypertension, palpitations, sweating) 1
- Late-night salivary cortisol: When Cushing's syndrome is suspected (central obesity, facial rounding, striae) 1
Imaging Studies (When Indicated)
- Renal ultrasound/Doppler: To evaluate for renal parenchymal disease or renal artery stenosis 1
- CT/MR angiography: For suspected renal artery stenosis or adrenal pathology 1
- Brain CT/MRI: When hypertensive brain injury is suspected or in patients with neurological symptoms 1, 3
- Fundoscopy: To evaluate for retinal changes, hemorrhages, papilledema 1, 3
Clinical Pitfalls to Avoid
- Relying on urine dipstick alone instead of quantitative urinary albumin-to-creatinine ratio can miss early kidney damage 1, 2
- Failing to check standing blood pressure to detect orthostatic hypotension, especially in older adults 1, 2
- Not considering secondary causes of hypertension in patients with resistant hypertension, early-onset hypertension, or severe hypertension 1
- Overlooking the need for more extensive evaluation in patients with abnormal basic laboratory findings 1, 2
Risk Factor Assessment
- More than 50% of hypertensive patients have additional cardiovascular risk factors that should be identified and managed 1
- Common coexisting conditions include diabetes (15-20%), lipid disorders (30%), obesity (40%), hyperuricemia (25%), and metabolic syndrome (40%) 1
- Identifying these risk factors is crucial for comprehensive cardiovascular risk assessment and management 1