Laboratory Tests for Congestive Heart Failure
Initial Laboratory Panel (Class I Recommendation)
For all patients with newly diagnosed CHF, order a comprehensive initial laboratory panel including: hemoglobin/WBC, sodium, potassium, urea, creatinine with eGFR, liver function tests (bilirubin, AST, ALT, GGTP), glucose, HbA1c, TSH, and iron studies (ferritin, transferrin saturation/TIBC). 1
Core Tests - Why Each Matters:
Hemoglobin/WBC: Identifies anemia that can mimic or worsen HF symptoms and affects prognosis 1, 2, 3
Renal function (creatinine/eGFR, BUN): Critical for medication dosing (ACE inhibitors, ARBs, diuretics), prognostic information, and detecting cardiorenal syndrome 1, 2, 3
Electrolytes (sodium, potassium): Essential for monitoring diuretic therapy and identifying disturbances affecting cardiac function 1, 2, 3
Liver function tests: Detect hepatic congestion from right heart failure and guide medication safety (especially amiodarone, warfarin) 1, 2
Glucose/HbA1c: Diabetes is both a risk factor and major comorbidity requiring management 1, 2, 3
TSH: Thyroid dysfunction is a reversible cause of HF that is easily missed 1, 2, 3
Iron studies (ferritin, TSAT/TIBC): Iron deficiency is common in HF and impacts symptoms and outcomes even without anemia 1
Natriuretic Peptides (Class IIa Recommendation)
BNP or NT-proBNP should be measured at initial assessment for diagnostic support, risk stratification, and establishing prognosis. 1, 2
- Measure at initial presentation, hospital admission, and prior to discharge 2
- Most useful as a "rule out" test due to high negative predictive value 2
- Critical caveat: Can be falsely elevated in advanced age, renal dysfunction, atrial fibrillation, pulmonary hypertension, and acute PE 2
- Critical caveat: May be falsely low in obesity, flash pulmonary edema, and HFpEF 2
Additional Tests Based on Clinical Suspicion (Class IIa)
Order these when specific pathology is suspected 1:
- Hemochromatosis screening: In younger patients with unexplained cardiomyopathy 2, 3
- HIV testing: In at-risk populations or unexplained cardiomyopathy 2, 3
- Rheumatologic disease testing: When clinical suspicion exists 2, 3
- Amyloidosis workup: In unexplained HFpEF, particularly older patients 2
- Cardiac troponin: For prognosis in acute decompensated HF and identifying ischemic etiology 2
Frequency of Monitoring
Renal function and electrolytes require serial monitoring in these specific situations: 2, 3
- After initiation or dose adjustment of diuretics, ACE inhibitors, ARBs, or aldosterone antagonists 1, 2
- During episodes of acute illness (especially diarrhea/vomiting causing sodium and water loss) 1
- When starting NSAIDs or adjusting diuretic doses 1
- In patients with severe HF requiring frequent medication adjustments 2
The 2016 ESC guidelines emphasize biochemical monitoring is particularly important during renin-angiotensin system blocker up-titration and during intercurrent illnesses. 1
Essential Non-Laboratory Tests
These must accompany laboratory evaluation 1, 2:
- 12-lead ECG: Required in all patients to determine rhythm, rate, QRS morphology/duration, and guide device therapy decisions 1, 2
- Chest X-ray: Detect alternative pulmonary diseases and identify pulmonary congestion (more useful in acute settings) 1, 2
- Echocardiography: Mandatory to confirm diagnosis and assess LVEF, cardiac structure, and valve function 2, 4
Common Pitfalls to Avoid
- Don't skip TSH testing - thyroid dysfunction is reversible and easily missed 3
- Don't omit calcium and magnesium from electrolyte panels - specifically recommended in guidelines 3
- Don't rely solely on BNP/NT-proBNP - interpret in clinical context given multiple confounders 2
- Don't forget iron studies - iron deficiency treatment improves outcomes even without anemia 1
- Monitor for hyponatremia, worsening renal function, and hyperkalemia - these complicate HF management 2