White Blood Cells (WBC), Stool

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% and specificity 88% for bacterial diarrhea (Shigella, Salmonella, Campylobacter). Positive predictive value was 59%. Negative predicative value was 97%. 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 preëmpt the use of culture.² Similar findings including a sensitivity of 81% and specificity 74% were observed when both tests were positive.³