The quantikine Human atrial natriuretic peptide immunoassay is a 4.5 hour solid phase elisa designed to measure anti-thrombin receptor levels in cell culture supernates, serum, and plasma. It contains e. Coli-expressed recombinant Human atrial natriuretic peptide and antibodies raised against recombinant Human atrial natriuretic peptide. This immunoassay has been shown to accurately quantitate the recombinant factor. Results obtained using natural Human atrial natriuretic peptide showed dose response curves that were parallel to the standard curves obtained using the recombinant quantikine kit standards. These results indicate that this kit can be used to determine relative mass values for natural Human atrial natriuretic peptide