What diagnostic tests should be ordered for a patient with chronic uncontrolled hypertension (high blood pressure)?

Diagnostic Testing for Chronic Uncontrolled Hypertension

For chronic uncontrolled hypertension, order basic laboratory tests (sodium, potassium, creatinine with eGFR, fasting glucose, lipid profile, urinalysis with albumin-to-creatinine ratio) and a 12-lead ECG as your initial workup, then proceed to additional testing based on clinical suspicion for target organ damage or secondary causes. 1, 2

Essential Initial Laboratory Tests

All patients with uncontrolled hypertension require the following baseline tests:

• Blood tests: Sodium, potassium, serum creatinine with estimated glomerular filtration rate (eGFR), fasting glucose (or HbA1c), and lipid profile (total cholesterol, LDL, HDL, triglycerides) 1, 2
• Urine tests: Dipstick urinalysis and urinary albumin-to-creatinine ratio to detect kidney damage 1, 2
• 12-lead ECG: To detect atrial fibrillation, left ventricular hypertrophy, and ischemic heart disease 1, 3, 2

Additional baseline tests when available include liver function tests, serum uric acid levels, and thyroid-stimulating hormone (TSH) 1, 2. These help identify cardiovascular risk factors, assess for target organ damage, and screen for secondary causes of hypertension 2.

Risk Stratification and Additional Testing

The extent of additional testing depends on your clinical assessment for hypertension-mediated organ damage (HMOD) and secondary hypertension.

When to Order Echocardiography:

• Mandatory: When ECG shows abnormalities, cardiac murmurs are present on examination, or patient has cardiac symptoms or signs of left ventricular dysfunction 1, 3, 2
• Consider: When detection of left ventricular hypertrophy would influence treatment decisions, even with normal ECG if resources permit 1, 3

When to Suspect Secondary Hypertension:

Order targeted testing when clinical features suggest specific causes 1:

• Primary aldosteronism: Hypokalemia, resistant hypertension → aldosterone-renin ratio 1, 2
• Pheochromocytoma: Sweating, palpitations, frequent headaches → plasma free metanephrines 1
• Cushing syndrome: Fatty deposits, colored striae, central obesity → late-night salivary cortisol or other cortisol excess screening 1
• Renal artery stenosis: Flash pulmonary edema, abdominal bruits → renal artery ultrasound/Duplex or CT/MR angiography 1, 2
• Obstructive sleep apnea: Snoring, daytime sleepiness, neck circumference >40 cm → sleep study 1

Additional Imaging When Indicated:

• Renal ultrasound: For suspected kidney disease, chronic kidney disease assessment, or resistant hypertension 1, 3, 2
• Carotid ultrasound: May be considered to detect atherosclerotic plaques or stenosis in patients with documented vascular disease elsewhere 1
• Fundoscopy: Essential in severe/uncontrolled hypertension to assess for retinal changes, hemorrhages, or papilledema 1, 2

Clinical Interpretation Pitfalls

Key laboratory findings that guide management:

• Hypokalemia suggests primary aldosteronism, while hyperkalemia indicates kidney dysfunction or medication effects 2
• Elevated creatinine or reduced eGFR (<60 mL/min/1.73m²) indicates moderate-to-severe chronic kidney disease and significantly influences treatment decisions 1, 2
• Proteinuria or albuminuria indicates kidney damage and serves as an independent cardiovascular risk factor 2
• Elevated glucose or HbA1c identifies comorbid diabetes, which significantly increases cardiovascular risk and lowers treatment thresholds 2

Important caveats:

• Cardiac biomarkers (troponin, NT-proBNP) should be interpreted cautiously in patients with reduced kidney function, as they may be elevated due to decreased renal clearance rather than cardiac damage 3
• Obtain baseline electrolytes and kidney function before initiating diuretics or renin-angiotensin system blockers to monitor for medication side effects 2
• More than 50% of hypertensive patients have additional cardiovascular risk factors (diabetes 15-20%, dyslipidemia 30%, obesity 40%), which proportionally increase risk of coronary, cerebrovascular, and renal diseases 1

Algorithmic Approach to Testing

Step 1: Order basic labs (electrolytes, creatinine/eGFR, glucose, lipids, urinalysis with albumin-to-creatinine ratio) and 12-lead ECG for all patients 1, 2

Step 2: If ECG abnormal, cardiac symptoms present, or murmurs detected → order echocardiography 1, 3, 2

Step 3: If clinical features suggest secondary hypertension → order targeted testing (aldosterone-renin ratio, plasma metanephrines, cortisol screening, renal imaging) 1, 2

Step 4: If severe hypertension (≥180/110 mmHg) → add fundoscopy and consider more comprehensive cardiovascular assessment 1, 2

Step 5: If resistant hypertension (uncontrolled on ≥3 medications) → screen aggressively for secondary causes and consider renal imaging 1, 2