In this sandwich ELISA, NAG-1 was captured from human serum using the following antibodies (see Related Products below): anti-NAG-1/GDF15 (C terminal specific), anti-NAG-1/GDF15 (N terminal specific (PAN)), anti-NAG-1/GDF15 (H-variant) and anti-NAG-1/GDF15 (D-variant) polyclonal antibodies. Micro titer plates were coated with capture antibody at 1 µg/mL. Control plates received PBS only (data not shown). After overnight incubation and blocking, independent experiments using 20 random normal human sera were performed. Neat normal sera were applied and incubated for 1 h at 37 °C. After washing, HRP conjugated anti-NAG-1/GDF15 (C terminal specific) antibody was added for detection at 100 µL per well at 1 µg/mL. Following further incubation for 1 hr at 37°C, the plates were washed and TMBE was added as an HRP substrate for 30 min. The reaction was stopped by 1 M H2SO4 and values were measured at 450nm.