Urinalysis and Body Fluids 6th Edition by Majorie DiLorenzo, Susan Strasinger

Exercise 46

Guaiac tests for detecting occult blood rely on the:

A. Reaction of hemoglobin with hydrogen peroxide

B. Pseudoperoxidase activity of hemoglobin

C. Reaction of hemoglobin with ortho-toluidine

D. Pseudoperoxidase activity of hydrogen peroxide

Step 1 of 2

gFOBT (guaiac-based Fecal Occult Blood Test):

• gFOBT is frequently used test to detect fecal occult blood

• The test depends on “pseudoperoxidase activity” of hemoglobin

• When hydrogen peroxide is added with the hemoglobin due to pseudoperoxidase activity the colorless compound is oxidized and produce a colored compound

• Guaiac, a less sensitive reagent is preferred for routine analysis

• To prevent false-positive reaction, the test sensitivity is reduced by altering the purity and amount of the guaiac reagent

Therefore, gFOBT test rely on “pseudoperoxidase activity” of hemoglobin to detect the occult blood. Hence, the correct answer is option.