NPPB and congestive heart failure: The positive correlation between plasma and urine (fresh and frozen) NT-proBNP concentrations in CHF patients is demonstrated in previous studies with correlation coefficients ranging between r=0.53 and r=0.78.15,17,18,21 The report by Jungbauer et al.22 about fresh urine NT-proBNP showed a correlation coefficient 0.79.