What labs are recommended for a patient with essential hypertension?

Laboratory Investigations for Essential Hypertension

All patients with essential hypertension require a core set of basic laboratory tests to assess cardiovascular risk, detect target organ damage, and screen for secondary causes: sodium, potassium, serum creatinine with eGFR, lipid profile, fasting glucose, urinalysis (dipstick), and 12-lead ECG. 1

Core Laboratory Panel (Required for All Patients)

Blood Tests

• Sodium and potassium: Essential electrolytes to screen for primary aldosteronism (unprovoked hypokalemia suggests this diagnosis) and assess baseline renal function 1, 2
• Serum creatinine and estimated glomerular filtration rate (eGFR): Identifies chronic kidney disease (eGFR <60 ml/min/1.73m² indicates moderate-severe CKD and hypertension-mediated organ damage) 1
• Lipid profile: Detects dyslipidemia present in 30% of hypertensive patients, which proportionally increases cardiovascular risk 1
• Fasting glucose: Screens for diabetes, present in 15-20% of hypertensive patients and a major cardiovascular risk modifier 1

Urine Test

• Dipstick urinalysis: Screens for proteinuria and hematuria indicating renal parenchymal disease or hypertension-mediated kidney damage 1, 3

Electrocardiogram

• 12-lead ECG: Detects left ventricular hypertrophy, atrial fibrillation, and ischemic heart disease—all clinically silent conditions that dramatically alter prognosis and treatment 1, 3

Additional Laboratory Tests (When Available or Indicated)

Cardiovascular Risk Assessment

• Serum uric acid: Common in hypertensive patients (25% have hyperuricemia) and represents an additional cardiovascular risk factor 1
• Liver function tests: Part of comprehensive metabolic assessment, particularly before initiating certain antihypertensive medications 1

Enhanced Renal Assessment

• Urinary albumin-to-creatinine ratio: More sensitive than dipstick for detecting early kidney damage and should be measured when available 1, 4

Screening for Secondary Hypertension (Selective Testing)

The 2024 European Society of Cardiology guidelines represent a major paradigm shift by recommending aldosterone-to-renin ratio measurement in all adults with confirmed hypertension (Class IIa recommendation), departing from traditional selective screening 2. However, other specialized tests remain indicated only when clinical clues suggest specific secondary causes:

When to Screen for Specific Secondary Causes

• Aldosterone-renin ratio: Now recommended for all hypertensive patients per ESC 2024; particularly important if unprovoked hypokalemia, muscle weakness, tetany, or resistant hypertension present 1, 2, 4
• Plasma free metanephrines or 24-hour urinary catecholamines: Only if episodic sweating, palpitations, or frequent headaches suggest pheochromocytoma 1, 2
• Late-night salivary cortisol or other cortisol screening: Only if physical stigmata (fatty deposits, colored striae, central obesity) suggest Cushing syndrome 1
• Renal artery imaging (Doppler ultrasound, CT/MR angiography): Only if onset after age 50, flash pulmonary edema, or abdominal bruit suggest renovascular disease 2, 4

Clinical Context for Laboratory Selection

Essential vs. Secondary Hypertension

More than 90% of hypertension is essential (primary), but secondary causes affect 5-10% overall and increase substantially in resistant hypertension populations 2. The basic laboratory panel above is sufficient for essential hypertension, while specialized testing should be reserved for specific clinical scenarios 1, 5, 6.

Red Flags Requiring Expanded Workup

• Age of onset <30 years or >50 years 2, 4
• Resistant hypertension (>140/90 mmHg despite ≥3 medications including a diuretic) 2, 4
• Sudden onset or deterioration of previously controlled hypertension 2, 4
• Hypertensive urgency/emergency 2, 3
• Target organ damage disproportionate to hypertension duration 2

Critical Pitfalls to Avoid

Common Errors in Laboratory Evaluation

• Ordering extensive secondary hypertension workup without clinical clues: This approach is expensive, time-consuming, and exposes patients to unnecessary risk 7, 5, 6
• Skipping urinalysis: This is the single most sensitive screening test for renal damage and has 100% sensitivity for ruling out acute creatinine elevation 3
• Failing to check medication history before extensive workup: Oral contraceptives, NSAIDs, decongestants, glucocorticoids, cyclosporine, cocaine, and amphetamines all cause drug-induced hypertension—a common and costly diagnostic error 2
• Assuming normal physical exam excludes organ damage: Physical findings lag behind actual organ injury; laboratory testing is essential because end-organ damage is often clinically silent and present in 5-33% of asymptomatic patients 3

Practical Algorithm

1. Initial screening: Perform core laboratory panel (electrolytes, creatinine/eGFR, lipids, glucose, urinalysis, ECG) in all hypertensive patients 1
2. Risk stratification: Use laboratory results to identify additional cardiovascular risk factors (diabetes, dyslipidemia, CKD) that proportionally increase morbidity and mortality 1
3. Selective advanced testing: Reserve specialized tests for secondary hypertension only when clinical clues warrant further investigation 2, 5, 6
4. Medication review: Always exclude drug-induced causes before proceeding with expensive secondary hypertension workup 2