Chromogranin A

This ELISA (enzyme-linked immunosorbent assay) kit is intended for the quantitative determination of human chromogranin A levels in EDTA-plasma and serum samples. This assay exclusively measures human chromogranin A without the high dose “hook” effect up to 1,000,000 ng/mL. This test may be used as an aid for detecting patients with pheochromocytoma and neuroendocrine tumors (carcinoids). This ELISA is designed, developed and produced for the quantitative measurement of human chromogranin A in EDTA-plasma or serum sample. The assay utilizes the two-site “sandwich” technique with two selected antibodies that bind to different epitopes of human chromogranin A. Assay standards, controls and patient samples are added directly to wells of microplate that is coated with a polyclonal chromogranin A antibody. After the first incubation period, the antibody on the wall of microtiter well captures human chromogranin A in the sample and unbound protein in each microtiter well is washed away. Then a horseradish peroxidase (HRP)-labeled monoclonal anti-human chromogranin A antibody is added to each microtiter well and a “sandwich” of “monoclonal antibody - human chromogranin A – polyclonal antibody” is formed. The unbound monoclonal antibody is removed in the subsequent washing step. For the detection of this immunocomplex, the well is incubated with a substrate solution in a timed reaction and then measured in a spectrophotometric microplate reader. The enzymatic activity of the immunocomplex bound to the chromogranin A on the wall of the microtiter well is directly proportional to the amount of chromogranin A in the sample. A standard curve is generated by plotting the absorbance versus the respective human chromogranin A concentration for each standard with a 4 parameter curve fit. The concentration of human chromogranin A in test samples is determined directly from this standard curve.