cm - chemical test for stool specimen
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CHEMICAL TEST FOR STOOL SPECIMENMary Christelle G. Aquitania
UST Medical Techonology Intern
Fecal Occult Blood Test Quantitative Fecal Fat Testing
Fecal Occult Blood Test
Most frequently performed test Positive result suggests
BLEEDING of GI tract UPPER: black, tarry stool LOWER: overly bloody stool
Early detection of colorectal cancer
>2.5ml/150g stool
Fecal Occult Blood Test
Mechanism PSUEDOPEROXIDASE ACTIVITY OF
HEMOGLOBIN
Hemoglobin H2O2 Guiac
Oxidized Guiac +
H2O
Pseudo 0
peroxidase
Fecal Occult Blood Test
AVOID [3 days] Red meat Horseradish Melons Raw broccoli Cauliflower Turnip
Fecal Occult Blood Test
AVOID [7 days] Aspirin NSAIDS
AVOID [3 days] Vitamin C Iron supplements
Fecal Occult Blood Test
PROCEDURE - Materials Filter Paper Reagent A: Guiac Reagent B: Hydrogen peroxide Applicator stick
Fecal Occult Blood Test
PROCEDURE Place a smear of stool specimen on the filter
paper in circular form. Add 2 gtts. of Reagent A then Reagent B on
the smear. Read after 1 minute.
Fecal Occult Blood Test
INTERPRETATION
POSITIVE: A trace of blue on the stool
NEGATIVE: No change of color
Fecal Occult Blood Test
FALSE POSITIVE Aspirin & anti-
inflammatory medication
Red meat Horseradish Raw broccoli,
cauliflower, radish, turnip
Melon Menstrual &
hemorrhoid contamination
FALSE NEGATIVE Vitamin C >
250mg/day Iron supplements
Containing VIT C
Developments
Hemoquant Fluorometric test for hemoglobin and
porphyrin Immunochemical FOBT
Specific for globin of human Hb Uses Anti-human hemoglobin antibodies
Hemoccult ICT Uses Anti-human hemoglobin antibodies Early detection of colon cancer OK: patients taking aspirin and other anti-
inflammatory medication Does not detect other source of bleeding
Quantitative Fecal Fat Testing Confirmatory test for steatorrhea (Gold Std. -
fat) Collection: at least 3-day specimen. Patient: maintain a regulated intake of fat (100
g/day) prior to and during the specimen collection period
Containers: Paints cans Specimen must be homogenized prior to analysis(conventional paint-can shaker)
Refrigeration: prevents bacterial degeneration.
Quantitative Fecal Fat Testing Routine Method: Van de Kamer titration
Gravimetric methods are also available Fecal lipids are converted to fatty acids and
titrated to a neutral endpoint with sodium hydroxide.
Manner of reporting: gram of fat coefficient of fat retention per 24 hours.
Quantitative Fecal Fat Testing Routine Method: Van de Kamer titration
Normal values based on a 100 g/day intake are 1 to 6 g/day or a coefficient of fat retention of at least 95%. The coefficient of fat retention is calculated as follows:
Quantitative Fecal Fat Testing Acid steatocrit
rapid test: estimates the amount of fat excretion
similar to the microhematocrit test more convenient than a 72-hou stool
collection
reliable tool to monitor a patient’s response to therapy and screen for steatorrhea in pediatric population