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Fecal Leukocytes

The presence of fecal leukocytes indicates bowel mucosal inflammation, which occurs in invasive bacterial enteritis and ulcerative colitis. The sensitivity of the fecal leukocyte test is approximately 70% for diarrheal disease caused by Shigella, but lower for other bacterial pathogens. Even in a children’s hospital setting, the sensitivity of fecal leukocyte test for bacterial pathogens is only 65%. The fecal leukocyte test has low sensitivity because leukocytes degrade rapidly in stored samples, are only present intermittently, and are unevenly distributed in stool. Toxins of organisms, such as Clostridium difficile, can destroy fecal leukocytes. Because of this mediocre test performance, the most recent guidelines for the management of diarrhea from the American College of Gastroenterology (ACG) and the Infectious Diseases Society of America (IDSA) do not recommend performing the fecal leukocyte assay.

Fecal lactoferrin, a glycoprotein present in neutrophil granules, is purportedly a more sensitive marker of intestinal inflammation. Recent guidelines, however, state that even fecal lactoferrin testing is imprecise and unnecessary. ACG does not recommend the use of lactoferrin to establish the cause of acute diarrhea. Fecal leukocyte or lactoferrin testing also has no defined role in the management of inflammatory bowel disease.

Fecal calprotectin, another marker of intestinal inflammation, is largely used as an ad- junctive test in the management of inflammatory bowel disease. Neither fecal lactoferrin nor fecal calprotectin testing are likely to have a role in the management of patients with acute diarrhea because of the inability of these test results to guide treatment. This lack of utility is attributable to the inability of these tests to predict stool culture results and response to antimicrobials, not necessarily their inability to detect inflammation.

Newer multiplex molecular tests for enteric pathogens cannot accurately distinguish between infection and colonization, shedding of organisms after an infection has resolved, and remnant nucleic acid. There are currently no data to support the use of fecal leukocyte assays to confirm the pathogenicity of molecularly detected pathogens.

Because of these limitations, a recent opinion article published in JAMA called on clinicians, pathologists, clinical laboratories, professional societies and health care systems to discontinue the use of the fecal leukocyte assay.


HerbertME.Medical myth:measuring white blood cells in the stools is useful in the management of acute diarrhea. West J Med. 2000;172(6):414.

Pickering LK, DuPont HL, Olarte J, Conklin R, Ericsson C. Fecal leukocytes in enteric infections. Am J Clin Pathol. 1977;68(5):562-565

Granville LA, Cernoch P, Land GA, Davis JR. Performance assessment of the fecal leukocyte test for inpatients. J Clin Microbiol. 2004;42(3):1254-1256.

Riddle MS, DuPont HL, Connor BA. ACG clinical guideline: diagnosis, treatment, and prevention of acute diarrheal infections in adults. Am J Gastroenterol. 2016;111(5):602-622.

Shane AL, Mody RK, Crump JA, et al. 2017 Infectious Diseases Society of America clinical practice guidelines for the diagnosis and management of infectious diarrhea. Clin Infect Dis. 2017;65(12):e45-e80

Gupta A, Johnson DH and Agrawal D. Devolution and Devaluation of Fecal Leukocyte Testing: A 100-Year History. JAMA published online July 9, 2018, E1-E2.





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