White Blood Cells (WBC), Stool

Methodology: 
Simple stain
Performed: 
Monday - Friday
Use: 
This test is used to aassist in the differential diagnosis of diarrheal disease.
 

Limitations

Between 10 and 15 percent of stools that yield an invasive bacterial pathogen have an absence of fecal leukocytes. Fecal leukocytes are present in idiopathic inflammatory bowel disease.
Specimen Requirements: 
Type: Stool
 
Container/Tube: Parasite (O & P) transport (PVA) vial only
 

Sample Volume: 1 g

Minimum Volume: 0.7 mL (Repeat testing is not possible with this specimen volume.)

Storage: Store specimens at room temperature.

Rejection Criteria:
  • Quantity not sufficient for analysis
  • Improper specimen transport device
  • Improper labeling
  • Unlabeled specimen or name discrepancy between specimen and request label
  • Specimen received after prolonged delay
CPT Code (s): 
89055
Notes: 

UFHPL Test #: 78095

UFHPL Epic order code: LAB265

Conditions associated with marked fecal leukocytes, blood and mucus include:

  • Diffuse antibiotic associated colitis;
  • Ulcerative colitis;
  • Shigellosis;
  • Salmonellosis;
  • Campylobacter; and
  • Yersinia infection.

Salmonella typhi may evoke a monocyte response. Conditions associated with modest numbers of fecal leukocytes include early shigellosis involving small bowel, antibiotic associated colitis, and amebiasis. Conditions associated with an absence of fecal leukocytes include toxigenic bacterial infection, giardiasis and viral infections.
 
In a review, the methylene blue stain for polymorpholeukocytes had a high sensitivity (85 percent) and specificity (88 percent) for bacterial diarrhea (Shigella, Salmonella, Campylobacter). Positive predictive value was 59 percent. Negative predicative value was 97 percent. Combined with a history of abrupt onset, greater than four stools per day and no vomiting before the onset of diarrhea the stool methylene blue stain for fecal polymorphonuclear leukocytes was a very effective presumptive diagnostic test for bacterial diarrhea.1
 
A positive occult blood test may also be suggestive of acute bacterial diarrhea. Neither method is sufficiently sensitive or specific to preempt the use of culture.2 Similar findings including a sensitivity of 81 percent and specificity 74 percent were observed when both tests were positive.3
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