What is the likelihood of heart failure (HF) in a patient with an NT-proBNP (N-terminal pro b-type natriuretic peptide) level of 125 pg/mL?

Interpretation of NT-proBNP Level of 125 pg/mL for Heart Failure Assessment

An NT-proBNP level of 125 pg/mL effectively rules out chronic heart failure, as this value is at the exact threshold used to exclude chronic HF in non-acute settings. 1

Diagnostic Value of NT-proBNP at 125 pg/mL

Rule-Out Value

• NT-proBNP of 125 pg/mL is the established cut-off point for excluding chronic heart failure in non-acute settings 1
• This threshold has a high negative predictive value (94-98%), making it excellent for ruling out heart failure 1
• For acute heart failure assessment, a higher threshold of 300 pg/mL is used for exclusion 1

Clinical Context Considerations

• While 125 pg/mL is exactly at the threshold, interpretation should consider:
  • Age: Age-adjusted thresholds are more specific for diagnosing acute HF (450 pg/mL for <50 years, 900 pg/mL for 50-75 years, and 1800 pg/mL for >75 years) 1
  • Body mass index: Obesity can lower NT-proBNP levels, potentially causing false negatives 2
  • Renal function: Impaired kidney function (GFR <60 mL/min/1.73m²) can elevate NT-proBNP levels 1

Algorithm for Clinical Decision-Making

1. For chronic heart failure assessment:

   • NT-proBNP = 125 pg/mL → At the exact threshold for ruling out chronic HF
   • If patient has no symptoms or signs of HF → Heart failure is effectively ruled out
   • If patient has symptoms or signs of HF → Further cardiac evaluation is warranted despite borderline value

2. For acute heart failure assessment:

   • NT-proBNP = 125 pg/mL → Well below the 300 pg/mL threshold for ruling out acute HF
   • Acute heart failure is very unlikely regardless of age 1

3. Special considerations:

   • In obese patients (BMI >35 kg/m²): 125 pg/mL may not reliably exclude HF, as obesity can lower NT-proBNP levels by 20-30% 1, 2
   • In elderly patients (>75 years): 125 pg/mL strongly excludes HF, as age typically increases NT-proBNP levels 1
   • In patients with atrial fibrillation: 125 pg/mL strongly excludes HF, as AF typically increases NT-proBNP levels by 20-30% 1

Clinical Implications

• The 2016 ESC guidelines recommend NT-proBNP testing as an initial diagnostic step when echocardiography is not immediately available 1
• A value of 125 pg/mL has high negative predictive value but lower positive predictive value (44-57%) in non-acute settings 1
• Even with a borderline value, clinical assessment remains crucial - symptoms (dyspnea, orthopnea) and signs (edema, jugular venous distention) should guide further evaluation 3

Pitfalls and Caveats

• NT-proBNP at exactly 125 pg/mL represents a borderline value that warrants careful interpretation
• False negatives can occur in obese patients, where HFpEF may be present despite NT-proBNP levels below 125 pg/mL 2
• False positives can occur with advanced age, renal dysfunction, and atrial fibrillation 1
• NT-proBNP should not be used in isolation but interpreted alongside clinical findings and other diagnostic tests, particularly echocardiography 1, 3

In summary, an NT-proBNP level of 125 pg/mL effectively rules out chronic heart failure in most clinical scenarios, but interpretation should be adjusted based on patient characteristics, particularly obesity, which can lead to falsely low values.