fecal analysis flashcards

What is the normal color of stool and what causes it?

Brown, due to urobilin from bile pigments.

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What does pale or clay-colored stool indicate?

Post-hepatic (bile duct) obstruction.

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What does black, tarry stool (melena) indicate?

Upper GI bleeding (or certain foods/meds like iron, beets).

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What does bright red stool indicate?

Lower GI bleeding (e.g., hemorrhoids, colon lesion).

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What is the normal consistency and appearance of stool?

Formed, cylindrical masses.

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What does mucus in stool indicate?

Intestinal irritation, inflammation, colitis, or dysentery.

Define diarrhea.

200g/day, increased water content and frequency (>3x/day).

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What causes secretory diarrhea?

Increased intestinal secretions (bacterial/viral toxins, IBD, laxatives, endocrine disorders).

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What causes osmotic diarrhea?

Poor absorption → increased water retention (lactose intolerance, antibiotics, antacids).

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What causes altered motility diarrhea?

Irritable bowel syndrome, stress, exercise, certain foods.

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Define steatorrhea.

Excess fat in stool (>6 g/day); due to malabsorption or pancreatic insufficiency.

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What is the principle behind the microscopic fecal WBC test?

Detection of neutrophils in stool using Wright or methylene blue stain; presence indicates intestinal inflammation.

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What is the reference range for fecal leukocytes?

None present.

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What organisms cause inflammatory diarrhea with fecal WBCs?

Shigella, Salmonella, Campylobacter, C. difficile.

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What is the principle behind the LEUKO EZ VUE® test?

Immunochromatographic detection of lactoferrin, a stable neutrophil protein, using anti-lactoferrin antibodies conjugated to gold particles.

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What does a positive LEUKO EZ VUE® test look like?

Two red lines (test + control).

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What does a negative LEUKO EZ VUE® test look like?

One red line in the control area only.

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Why is lactoferrin used instead of whole WBCs?

It remains stable even when WBCs are lysed by toxins (e.g., C. difficile).

What is the principle behind the Guaiac fecal occult blood test (Hemoccult®)?

Detects the pseudo-peroxidase activity of heme; oxidizes guaiac in presence of hydrogen peroxide → blue color = positive.

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What are dietary restrictions before Guaiac testing?

Avoid red meat, certain fruits/vegetables, vitamin C, iron, aspirin, and NSAIDs.

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How many stool samples should be collected for a Guaiac test?

Three samples from three separate bowel movements.

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What does a blue color on Hemoccult® indicate?

Positive for occult blood.

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What is the principle behind the Immunochemical Fecal Occult Blood Test (Hemoccult ICT / iFOBT)?

Immunochromatographic detection of human hemoglobin globin portion using anti-human Hgb antibodies.

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What is a key difference between Guaiac and iFOBT?

iFOBT is specific for human blood → no dietary restrictions; detects lower GI bleeding.

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What conditions can iFOBT help screen for?

Diverticulitis, ulcerative colitis, polyps, adenomas, colorectal cancer.

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What does a positive iFOBT result show?

Visible red line in the test window (plus control line).

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What does a negative iFOBT result show?

Only the control line appears.

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What is the principle behind the qualitative fecal fat test?

Fat globules are stained with Sudan III; viewed microscopically to detect fat malabsorption or pancreatic insufficiency.

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How is fecal fat reported?

60 fat globules per high power field = abnormal (steatorrhea).

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What does an increase in fecal fat indicate?

Malabsorption or maldigestion (e.g., cystic fibrosis, pancreatitis).

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What is the principle behind the fecal reducing substances test?

Benedict’s copper reduction test detects reducing sugars (e.g., lactose, glucose) that indicate carbohydrate malabsorption.

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What is the principle behind the fecal pH test?

Stool is mixed with water and tested; acidic pH indicates fermentation of unabsorbed carbohydrates.

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What is normal fecal pH?

7.0–7.5.

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What pH suggests carbohydrate malabsorption?

<5.6 (acidic stool). ⸻

What causes C. difficile infection?

Overgrowth of C. difficile after antibiotic use; spores spread via contaminated surfaces/hands.

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What toxins does C. difficile produce?

Toxins A & B.

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What is the principle behind the ImmunoCard Toxins A&B test?

Enzyme immunoassay (EIA) using antibodies to toxins A & B conjugated to peroxidase; color change indicates toxin presence.

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What does a positive C. difficile toxin test indicate?

Active infection causing antibiotic-associated diarrhea (CDAD).

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What are clinical signs of C. difficile infection?

Watery diarrhea, fever, nausea, abdominal pain; may progress to sepsis or colon perforation.

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How should stool samples be collected?

In a clean, leak-proof container; avoid urine, toilet water, tissue.

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How long are fecal samples stable for WBC testing?

Must be tested within minutes (WBCs lyse quickly).

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How long are fecal samples stable for lactoferrin testing (LEUKO EZ VUE)?

Up to 2 weeks refrigerated (2–8°C), longer if frozen (-20°C).

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How long are samples stable for iFOBT testing?

Up to 14 days.

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What tests require multiple-day collections?

Quantitative fecal fat (2–3 days) and Guaiac occult blood (3 days).

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What fecal test is used for carbohydrate intolerance?

Fecal reducing substances test.

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What fecal test detects neutrophil granule protein?

LEUKO EZ VUE® (lactoferrin detection).

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What fecal test detects peroxidase activity?

Guaiac (Hemoccult®) occult blood test.

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What fecal test detects human hemoglobin specifically?

Immunochemical (Hemoccult ICT / iFOBT).

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What fecal test detects fat metabolism disorders?

Sudan III fecal fat stain.

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What fecal test detects toxins from C. difficile?

ImmunoCard Toxins A&B enzyme immunoassay.

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