Introduction: The plasma N-terminal probrain natriuretic peptide (NT-proBNP) level is an important diagnostic and prognostic marker of heart failure. Recent studies have suggested urinary NT-proBNP as a new and simple test for diagnosis of heart failure. We aim to compare diagnostic value of plasma, fresh and frozen urine levels of N-terminal probrain natriuretic peptide (NT-proBNP) for detecting heart failure.
Methods: Between January 2010 and January 2012, we measured urine and plasma levels of NTproBNP in 98 patients with chronic heart failure (CHF) and 29 age- and sex-matched healthy control subjects.
Results: There were significant correlations between plasma NT-proBNP and fresh (r=0.45, p<0.001) and frozen (r=0.42, p<0.001) urine NT-proBNP concentrations in CHF patients. Due to receiver operating curve analysis, fresh and frozen urine NT-proBNP could diagnose HF with are aunder curve (AUC) of 0.73±0.04 (p<0.001) and 0.65±0.05 (p=0.01) with sensitivity and specificity of 73.97%, 58.62%, and 65.31%, 62.07%, for a cut-off of 94.2 and 96 pg/mL, respectively. Plasma NT-proBNP had greater AUC (0.94±0.02, p<0.001) and better sensitivity and specificity (94.9%, 89.66% for cut-off of 414.5 pg/mL). There was no significant correlation between LVEF and plasma, fresh and frozen urine NT-proBNP levels in CHF patients.
Conclusion: Plasma NT-proBNP is still the best diagnostic marker with high sensitivity and specificity; however, urinary especially fresh urine NT-proBNP may be a surrogate to plasma NTproBNP for diagnosing HF with acceptable accuracy.
Keywords: Fresh Urine; Frozen Urine; Heart Failure; NT-proBNP; Plasma.