As of August 1, 2000, the clinical microbiology laboratory will discontinue microscopic analysis for fecal leukocytes except in unusual circumstances and then only after laboratory consultation. Studies in the literature have documented the lack of both the sensitivity and positive predictive value of this test in the diagnosis of enteric infections. In particular, Fan et al. (J. Clin. Microbiol. 31: 2233; 1993) reported that the presence of fecal leukocytes had just a 29% sensitivity value and a positive predictive value of 20% for presence of Shigella sp., Salmonella sp. and Campylobacter sp. Similarly, Marx et al. (Diagn. Microbiol. Infect. Dis. 16: 313; 1993) demonstrated that while fecal leukocytes retained morphology when refrigerated for an extended duration, the sensitivity and positive predictive values of fecal leukocytes in predicting results of a Clostridium difficile toxin assay were only 28% and 27%, respectively.
Please direct questions or comments regarding this policy to Gary V. Doern, Ph.D., (6-8616) Director, Clinical Microbiology Laboratory.