CM - Chemical Test for Stool Specimen

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


Mechanism PSUEDOPEROXIDASE ACTIVITY OF

HEMOGLOBIN

Hemoglobin H2O2 Guiac

Oxidized Guiac +

H2O

Pseudo 0

peroxidase


AVOID [3 days] Red meat Horseradish Melons Raw broccoli Cauliflower Turnip


AVOID [7 days] Aspirin NSAIDS

AVOID [3 days] Vitamin C Iron supplements


PROCEDURE - Materials Filter Paper Reagent A: Guiac Reagent B: Hydrogen peroxide Applicator stick


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.


INTERPRETATION

POSITIVE: A trace of blue on the stool

NEGATIVE: No change of color


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

CM - Chemical Test for Stool Specimen

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