The need to concentrate 10 of the saliva samples from HF patients before the detection of NT-proBNP, suggested the presence of endogenous salivary proteins or mucins (>30 K Dalton) that could reduce the analytical sensitivity or these proteins by blocking binding sites of our bead based salivary NT-proBNP immunoassay. The gene discussed is NPPB; the disease is hydrops fetalis.