Which laboratory tests are indicated for the initial work‑up of suspected heart failure?

Laboratory Tests for Heart Failure Work-Up

For patients with suspected heart failure, obtain a comprehensive laboratory panel including complete blood count, urinalysis, serum electrolytes (sodium, potassium, calcium, magnesium), blood urea nitrogen, serum creatinine, glucose, fasting lipid profile, liver function tests, iron studies (serum iron, ferritin, transferrin saturation), and thyroid-stimulating hormone, along with BNP or NT-proBNP measurement and a 12-lead ECG. 1

Core Laboratory Panel (Class I Recommendation)

The 2022 AHA/ACC/HFSA guidelines provide a Class I, Level C-EO recommendation for this comprehensive laboratory evaluation 1. This panel serves multiple critical purposes:

• Identifies comorbidities that influence treatment selection and prognosis
• Detects specific causes of heart failure requiring disease-specific therapies
• Establishes baseline values for monitoring treatment effects and adverse reactions
• Assesses suitability for guideline-directed medical therapy

Essential Components:

Hematologic and metabolic assessment:

• Complete blood count (anemia affects oxygen delivery and may worsen HF)
• Serum electrolytes including sodium, potassium, calcium, and magnesium
• Blood urea nitrogen and serum creatinine (renal function critical for medication dosing)
• Glucose and fasting lipid profile

Organ function and specific etiologies:

• Liver function tests (hepatic congestion, medication monitoring)
• Iron studies: serum iron, ferritin, transferrin saturation (iron deficiency common and treatable)
• Thyroid-stimulating hormone (both hypo- and hyperthyroidism cause HF)
• Urinalysis

Natriuretic Peptide Testing (Class I Recommendation)

BNP or NT-proBNP measurement is essential for diagnostic confirmation and risk stratification 1, 2. The 2022 guidelines give this a Class I, Level A recommendation for multiple indications:

Diagnostic Use:

• In acute dyspnea: BNP or NT-proBNP helps confirm or exclude HF diagnosis
• BNP cutoff: 100 pg/mL (sensitivity 90%, specificity 76%) 2
• NT-proBNP cutoffs:
  • <50 years: 450 pg/mL
  • ≥50 years: 900 pg/mL
  • Rule-out threshold: <300 pg/mL (negative predictive value 99%) 2

Prognostic Use:

• At hospital admission for risk stratification
• Pre-discharge to establish trajectory and post-discharge prognosis
• Serial measurements in chronic HF for ongoing risk assessment

Important Caveats:

Factors that lower natriuretic peptides:

• Obesity (interpret cautiously in obese patients)
• ACE inhibitors, ARBs, spironolactone treatment

Factors that elevate natriuretic peptides:

• Renal dysfunction
• Advanced age
• Atrial fibrillation
• Right ventricular dysfunction
• Pulmonary embolism

Do not use BNP/NT-proBNP when HF diagnosis is clinically obvious or as a replacement for echocardiography 2.

Electrocardiography (Class I Recommendation)

A 12-lead ECG is mandatory at initial evaluation 1. It provides:

• Rhythm assessment (atrial fibrillation common in HF)
• QRS duration and morphology (guides cardiac resynchronization therapy)
• Evidence of prior myocardial infarction
• Left ventricular hypertrophy patterns
• Conduction abnormalities

Additional Testing for Specific Etiologies

When clinical suspicion exists, pursue targeted testing for:

• Ischemic cardiomyopathy: Troponin, coronary angiography
• Cardiac amyloidosis: Serum/urine protein electrophoresis, free light chains
• Hemochromatosis: Iron studies, genetic testing
• Infectious causes: HIV, Chagas serology, COVID-19 testing
• Cardiotoxicity: History of chemotherapy exposure
• Peripartum cardiomyopathy: Recent pregnancy history

Practical Algorithm

1. Initial presentation: Order complete laboratory panel + BNP/NT-proBNP + ECG simultaneously
2. Interpret BNP/NT-proBNP: Use age-adjusted cutoffs; consider confounding factors
3. Review basic labs: Identify treatable comorbidities (anemia, thyroid disease, iron deficiency)
4. Assess for specific etiologies: Based on history and initial findings, add targeted tests
5. Repeat labs: Monitor electrolytes and renal function with diuretic initiation/titration

Common Pitfalls to Avoid

• Don't skip iron studies: Iron deficiency is highly prevalent and independently treatable in HF
• Don't dismiss low BNP in obesity: Obese patients may have falsely reassuring natriuretic peptide levels
• Don't order BNP when diagnosis is obvious: Wastes resources and doesn't change management
• Don't forget thyroid testing: Both hypo- and hyperthyroidism are reversible HF causes
• Don't use BNP as sole diagnostic tool: Must integrate with clinical assessment and echocardiography