Commonly marketed hemoglobin color tests are based on the pseudo-peroxidase activity of hemoglobulin (so-called guaiac-assay: oxidation of the substrate guajak results in a color change). Several food components can lead to false positive or false negative results (e.g. animal hemoglobin and myoglobin, peroxidases from animal or plant origin, or antioxidants, like vitamin C).
This hemoglobin ELISA is based on antibodies specific for human hemoglobin, whereby the above-mentioned contaminants do not affect the immunoassay. Therefore, no special diet is necessary, and certain drugs needn't be discontinued before analysis.
This hemoglobin ELISA is 100 times more sensitive than the guaiac-assay. This prevents false negative results and - based on the antibody selection - false positive results are almost eliminated.