NPPB and hepatitis C virus infection: This study and others have also found that hepatitis C infection and anemia are independently associated with elevated NT-proBNP, and renal disease is known to affect NT-proBNP levels.[34,46,47] We excluded persons with reduced renal function and used the calculated creatinine clearance in modeling to eliminate potential confounding from significant renal disease that would alter NT-proBNP level and mortality; however, there may be residual confounding from these factors that could explain the association we find between NT-proBNP level and mortality.