A test that detects the presence of hidden (occult) blood in the stool. The stool guaiac is the most common form of Fecal Occult Blood test (FOBT) in use today. Brand names include: Hemoccult, Hemoccult SENSA, ColoScreen, ColoScreen-ES, Seracult, and Seracult Plus®. Laboratory procedures may vary. A small sample of the stool is placed on a special paper card, pad or wipe containing guaiac (a leuco-dye) then a chemical developer solution is put on top of the sample. If the card, pad, or cloth turns blue, there is blood in the stool and the stool is consider guaiac-positive.