BLOOD DETECTION

It is used for the detection of blood loss from gastrointestinal tract. The examination involves the use of guaiacol, a colorless reagentthat changes color, in the presence of samples containing peroxide such as heme and hydrogen peroxide. Hemoglobin and myoglobin from meat as well as peroxidase from vegetables (e.g. radish, turnip, cabbage, ανθοκράμβη, citrus fruit, broccoli) may give false positive results. Hence, a dietary preparationis suggested three days before sampling. Guaiacol test demands higher hemoglobin concentration than 10 mg/g of faeces, which stands for about 10 mL daily blood loss. In minor blood loss, heme decomposes in the colon resulting in false negative reaction. So if blood presence is suspected, more than one faecal samples should be examined.