Chemical Examination

• What are the 5 tests done in chemical examination of stool?

  Fecal pH and test for reducing sugar, fecal urobilinogen, sudan stain and estimation of fecal fat, fecal occult blood, and fecal osmotic gap
• PUSOO: mnemonics of clinical examination
• Fecal pH and test for reducing sugar: carbohydrate malabsorption
• Fecal urobilinogen: LIVER disease
• Sudan stain and estimation of fecal fat: FAT Malabsorption
• FECAL OCCULT BLOOD: Inflammatory, bowel disease, and neoplasm
• FECAL OSMOTIC GAP: Distinction between SECRETORY and OSMOTIC DIARRHEA
• Peroxidase-like activity of Hemoglobin: Principle behind occult blood test
• Hemoglobin has PEROXIDASE-LIKE ACTIVITY and releases OXYGEN from HYDROGEN PEROXIDE.
• Oxygen molecule then OXIDIZES the chemical reagent to produce a COLORED reaction product.
• What are different chemical reagents that can be used?

  Benzidine, orthotolidine, aminophenazone, or guaiac
• Which among the chemical reagents are CARCINOGENIC and are no longer used?

  Benzidine and orthotolidine
• Which among the chemical reagents are HIGLY SENSITIVE and can give FALSE-POSITIVE REACTION?

  Benzidine
• Since bleeding from lesion may be intermittent, repeated testing may be required.
• False-positive or false-negative: Ingestion of PEROXIDASE-CONTAINING Foods?

  False-positive
• Peroxidase-containing foods: red meat, fish, poultry, turnips, horseradish, cauliflower, spinach, or cucumber
• Diet should be free from peroxidase-containing foods for at least how many days prior to testing?

  3 days
• False-positive or false-negative: Drugs like ASPIRIN and other ANTI-INFLAMMATORY DRUGS?

  False-positive
• Drugs like aspirin and other anti-inflammatory drugs increases BLOOD LOSS from gastrointestinal tract in normal persons.
• False-positive or False-negative: Vitamin C?

  False-negative
• False-positive or false-negative: conversion of all HEMOGLOBIN to ACID HEMATIN during passage through the gastrointestinal tract?


  False-negative
• Do ACID HEMATIN have peroxidase-like activity?


  None