NT-proBNP Level of 152 pg/ml in a 70-Year-Old with One Kidney and Low Ferritin
A NT-proBNP level of 152 pg/ml is within normal range for a 70-year-old patient and does not indicate heart failure, as this value falls well below the age-specific upper limit of 225 pg/ml for females and 98 pg/ml for males over 60 years of age. 1
Interpretation of NT-proBNP Value
Age-Specific Reference Ranges
- For patients >60 years old:
- Males: <98 pg/ml
- Females: <225 pg/ml 1
Factors Affecting NT-proBNP Levels
- Chronic kidney disease can increase NT-proBNP levels due to decreased renal clearance 1
- Low ferritin (iron deficiency) can potentially increase NT-proBNP levels independent of heart failure status
- Having one kidney may affect NT-proBNP clearance, but the measured value remains within normal range
Clinical Significance
Diagnostic Thresholds
- For ruling out heart failure:
- NT-proBNP <300 pg/ml has a 98% negative predictive value 1
- Your value of 152 pg/ml is well below this threshold
Risk Stratification
- NT-proBNP values correlate with heart failure severity and prognosis:
- <300 pg/ml: Heart failure unlikely
- 300-900 pg/ml: "Gray zone" requiring clinical correlation
900-1800 pg/ml: Heart failure likely (age-dependent) 1
Special Considerations
Renal Function Impact
- Having one kidney may affect NT-proBNP clearance
- However, even with mild to moderate renal dysfunction, a value of 152 pg/ml remains reassuringly low
- For patients with significant renal dysfunction, higher NT-proBNP thresholds are used (typically 1200 pg/ml) 1
Iron Deficiency Considerations
- Low ferritin levels may be associated with:
- Anemia, which can increase cardiac workload
- Potential impact on myocardial function
- However, these factors would typically increase NT-proBNP, not decrease it
Clinical Approach
When to Consider Further Cardiac Evaluation
- Despite normal NT-proBNP, cardiac evaluation may be warranted if:
- Symptoms of heart failure are present (dyspnea, edema, fatigue)
- Physical examination findings suggest cardiac dysfunction
- Other cardiac risk factors exist
Monitoring Recommendations
- If clinically indicated, serial NT-proBNP measurements provide better prognostic information than a single value 2
- A significant increase (>70%) from baseline would warrant further investigation
Common Pitfalls in NT-proBNP Interpretation
- Failing to consider age, sex, and renal function when interpreting values 2
- Using BNP and NT-proBNP cutoffs interchangeably (they are not equivalent) 2
- Interpreting a single value without clinical context 2
- Not recognizing that NT-proBNP cannot reliably discriminate between systolic and diastolic heart failure 2
In conclusion, the NT-proBNP level of 152 pg/ml in this 70-year-old patient with one kidney and low ferritin levels is within normal range and does not suggest heart failure, regardless of gender.