What laboratories should be requested to assess for end organ damage in hypertension?

Laboratory Assessment for End Organ Damage in Hypertension

All hypertensive patients should undergo a core panel of laboratory tests including serum creatinine with eGFR, electrolytes (sodium and potassium), urinalysis by dipstick, and a 12-lead ECG to screen for hypertension-mediated organ damage (HMOD). 1

Essential Laboratory Tests (Perform in All Hypertensive Patients)

Blood Tests

• Serum creatinine with estimated glomerular filtration rate (eGFR): Identifies renal dysfunction; moderate-severe CKD (eGFR <60 ml/min/1.73m²) indicates significant organ damage 1
• Serum electrolytes: Sodium and potassium levels help detect secondary causes (hypokalemia suggests primary aldosteronism) and establish baseline before initiating diuretics or RAAS blockers 1, 2
• Fasting blood glucose or HbA1c: Identifies comorbid diabetes, present in 15-20% of hypertensive patients, which significantly increases cardiovascular risk 1, 2
• Lipid profile: Total cholesterol, LDL-C, HDL-C, and triglycerides assess cardiovascular risk and guide statin therapy decisions 1, 2

Urine Tests

• Dipstick urinalysis: Screens for proteinuria and hematuria; a negative dipstick for both protein and hematuria has 100% sensitivity for ruling out acute creatinine elevation 1
• Urinary albumin-to-creatinine ratio (UACR): More sensitive than dipstick for detecting early kidney damage; albuminuria (30-300 mg/g) indicates end-organ damage and heightened CVD risk 1, 2

Cardiac Assessment

• 12-lead ECG: Detects left ventricular hypertrophy (using Sokolow-Lyon index ≥35 mm or Cornell voltage criteria), atrial fibrillation, and ischemic heart disease 1, 2

Additional Laboratory Tests (When Available or Clinically Indicated)

• Serum uric acid: Hyperuricemia is present in 25% of hypertensive patients and represents an additional cardiovascular risk factor 1
• Liver function tests: Part of comprehensive metabolic assessment 1, 2
• Hemoglobin/hematocrit: Complete blood count for baseline assessment 1, 2
• Thyroid-stimulating hormone (TSH): Screens for thyroid disease as a secondary cause of hypertension 1, 2

Rationale for This Testing Strategy

The 2020 International Society of Hypertension guidelines emphasize that these tests serve three critical purposes: (1) detecting HMOD to refine cardiovascular risk stratification, (2) screening for secondary causes of hypertension, and (3) establishing baseline values before initiating antihypertensive medications 1

Renal assessment is particularly crucial because kidney damage is both a cause and consequence of hypertension; eGFR <60 ml/min/1.73m² and albuminuria are independent predictors of cardiovascular events 1, 3

ECG-detected left ventricular hypertrophy, while less sensitive than echocardiography, remains a valuable screening tool as it independently predicts cardiovascular events, particularly in patients over 55 years 1, 3

Extended Evaluation for Suspected HMOD

When initial screening suggests organ damage or in patients with resistant/complicated hypertension, additional testing should include 1:

• Echocardiography: More sensitive than ECG for detecting LVH (LVMI >115 g/m² in men, >95 g/m² in women); assesses LV geometry, systolic/diastolic function, and left atrial dilation 1
• Fundoscopy: Essential in severe hypertension (grade 2 or higher) to detect retinal hemorrhages, microaneurysms, or papilledema indicating hypertensive emergency 1, 4
• Renal imaging: Ultrasound or CT/MR angiography when secondary hypertension (renal artery stenosis, adrenal lesions) is suspected 1
• Brain MRI: Indicated for neurologic symptoms or visual disturbances to detect ischemic/hemorrhagic injury, white matter lesions, or microinfarcts 1, 4
• Carotid ultrasound: Assesses for atherosclerotic plaques and intima-media thickness in patients with neurologic symptoms 1
• Ankle-brachial index: Screens for peripheral artery disease 1

Common Pitfalls to Avoid

Do not rely solely on dipstick urinalysis for albuminuria screening—UACR is more sensitive for detecting early kidney damage and should be the preferred test in hypertensive patients 1

Avoid ordering routine chest radiographs—a 1978 study found that only 2 of 116 hypertensive patients had therapeutic interventions based on chest X-ray, and none influenced hypertension management 1

Do not skip baseline laboratory values before starting medications—electrolytes and renal function must be documented before initiating diuretics or RAAS blockers to monitor for medication side effects 2

Recognize that ECG has low sensitivity for LVH—if high clinical suspicion exists or ECG is abnormal, proceed directly to echocardiography for definitive assessment 1