What lab work indicates heart failure in adults with a history of hypertension, diabetes, or coronary artery disease?

Laboratory Workup for Heart Failure

The initial laboratory evaluation for suspected heart failure should include complete blood count, urinalysis, serum electrolytes (including calcium and magnesium), blood urea nitrogen, serum creatinine, fasting blood glucose (or glycohemoglobin), lipid profile, liver function tests, and thyroid-stimulating hormone. 1, 2

Core Laboratory Panel

The ACC/AHA guidelines establish a comprehensive baseline laboratory assessment that serves multiple purposes: identifying reversible causes, detecting comorbidities, and guiding treatment decisions 1.

Essential Tests

• Complete blood count (CBC): Identifies anemia, which can exacerbate heart failure symptoms or mimic the clinical presentation entirely 2, 3

• Serum electrolytes: Sodium, potassium, calcium, and magnesium levels reveal imbalances that may contribute to or result from heart failure, particularly in patients on diuretic therapy 1, 2

• Renal function tests (BUN and creatinine): Critical for evaluating cardiorenal syndrome, which is present in over half of heart failure patients and significantly affects prognosis and treatment decisions 2, 4

• Fasting blood glucose or HbA1c: Screens for diabetes mellitus, a major risk factor for heart failure development and progression 1, 2

• Lipid profile: Assesses cardiovascular risk and guides management of underlying coronary artery disease, the most common cause of heart failure 2, 3

• Liver function tests: Detects hepatic congestion from right-sided heart failure or identifies alternative causes of symptoms 1, 2

• Thyroid-stimulating hormone (TSH): Both hyperthyroidism and hypothyroidism can cause or contribute to heart failure; this is a reversible cause that must not be missed 1, 2

• Urinalysis: Screens for proteinuria indicating renal disease and other abnormalities 1, 2

Natriuretic Peptide Testing

BNP or NT-proBNP measurement is the single most powerful laboratory test for heart failure, particularly useful when the clinical diagnosis remains uncertain after initial evaluation. 1, 2

• BNP < 100 pg/mL or NT-proBNP < 300 pg/mL: Makes systolic heart failure very unlikely (negative LR = 0.11 for BNP and 0.09 for NT-proBNP), providing the best test to exclude heart failure 5, 6

• Elevated natriuretic peptides: Confirm the diagnosis and assist with risk stratification, with Level A evidence supporting their use 1

• Interpretation caveat: NT-proBNP levels are influenced by age, sex, body weight, and renal function, requiring clinical context for proper interpretation 2

• Quantitative value: Adding NT-proBNP to clinical assessment increases diagnostic accuracy (c-statistic from 0.83 to 0.86) with a net reclassification improvement of 69% 7

Additional Testing in Selected Patients

Beyond the core panel, specific clinical scenarios warrant targeted testing 1, 2:

• Hemochromatosis screening (fasting transferrin saturation): Consider in patients of Northern European descent, as iron overload causes reversible cardiomyopathy 2

• HIV testing: Recommended in high-risk patients, though HIV-related cardiomyopathy typically presents after other HIV manifestations 2

• Rheumatologic panel (ANA, rheumatoid factor): When connective tissue disease is suspected based on clinical features 2

• Pheochromocytoma screening (plasma or urine metanephrines): If clinical features suggest this diagnosis 2

• Chagas disease antibodies: In patients with travel to or immigration from endemic regions 2

Critical Non-Laboratory Components

While not laboratory tests, these are mandatory parts of the initial evaluation 1, 2:

• 12-lead electrocardiogram: Assesses for arrhythmias, conduction abnormalities, left ventricular hypertrophy, or prior myocardial infarction; any ECG abnormality increases probability of heart failure 2, 5

• Chest radiograph (PA and lateral): Evaluates for cardiomegaly, pulmonary congestion, and pleural effusions; pulmonary venous congestion has a positive LR of 12.0 2, 5

• Two-dimensional echocardiography with Doppler: The definitive diagnostic test to assess left ventricular ejection fraction, chamber size, wall thickness, and valve function 1, 2

Common Pitfalls

• Missing reversible causes: Failure to check TSH or screen for hemochromatosis in appropriate patients can miss treatable etiologies 2

• Ignoring renal function: Over half of heart failure patients have moderate-to-severe chronic kidney disease, which affects both prognosis and medication dosing 4

• Misinterpreting natriuretic peptides: BNP levels between 100-200 pg/mL have much lower diagnostic value (LR 0.29) than higher concentrations (1000-1500 pg/mL; LR 7.12), requiring clinical correlation 6

• Routine neurohormone measurement: Do not routinely measure circulating norepinephrine or endothelin levels, as this is not recommended 1