Background: Serum B-type natriuretic peptide (BNP) and the amino-terminal cleavage product of the prohormone (NT-proBNP) have been shown to be valuable parameters for the diagnosis of heart failure (HF) in the general population. Urinary BNP and NT-proBNP have also been suggested for diagnosis of HF. The present study investigated the diagnostic value of both serum and urinary NT-proBNP in selected groups of controls and patients diagnosed with HF.
Methods: Creatinine clearance and serum and urinary NT-proBNP were measured in 76 controls and in 47 patients diagnosed with HF (NYHA III and IV). Echocardiography was used to exclude cardiac dysfunction in the control population by the combined normality of left ventricular ejection fraction (LVEF), E/A ratio (echocardiographic early [E] and late, or atrial [A] phases of ventricular filling), deceleration time and LV mass index. All patients diagnosed with HF had LVEF <40%.
Results: NT-proBNP measurements in urine samples are subject to high variability. Receiver-operating characteristic area under the curve (AUC) for serum, urinary NT-proBNP and their products were 0.94, 0.72 and 0.93, respectively. Correction of urinary NT-proBNP for urinary creatinine content improved the AUC from 0.72 to 0.80. Negative predictive values for ruling out HF were 0.94, 0.67 and 0.89, respectively. Linear regression analysis revealed that creatinine clearance was more important in determining serum NT-proBNP concentrations than age.
Conclusions: Serum NT-proBNP is the best parameter to rule out HF. The product of the serum and urinary concentrations has equal value. Urinary NT-proBNP alone performs rather poorly. Renal function influences NT-proBNP concentrations more than age in this selected population.