NPPB and congestive heart failure: Among CHF patients, we observed a significant correlation between plasma NT-proBNP and fresh urine NT-proBNP (r=0.45, p<0.001), between plasma NT-proBNP and frozen urine NT-proBNP (r=0.42, p<0.001) and between fresh urine NT-proBNP and frozen urine NT-proBNP (r=0.94, p<0.001).