Rejection of Stool Specimens for Clostridium Difficile Testing
Patients with diarrhea caused by Clostridium difficile typically produce frequent stools that are watery, soft, or semi-formed in consistency. Patients who produce formed stool specimens are not likely to be infected with C. difficile. As such, the performance of C. difficile toxin testing on formed fecal samples represent an unnecessary use of laboratory resources and may occasionally result in false-positive test results.
In an effort to control these needless expenditures of laboratory time and resources, the following C. difficile Rejection Policy has been implemented by our Microbiology Department. In addition, because they may remain positive for weeks afterwards, specimens submitted within two weeks of a positive may be cancelled. A specimen for test-of-cure is contraindicated.
- Stool samples for Clostridium difficile toxin testing will only be performed on watery, soft, or semi-formed fecal samples. A watery, soft, of semi-formed stool sample is one in which the fecal material assumes the shape of the container used for specimen transport.
- Clostridium difficile toxin testing will not be performed on formed or hard stool samples or on patients who have had a positive specimen within the preceding two-week period.
- When such samples are received, the nursing floor (for inpatients) or the physician's office (for outpatients) will be notified by telephone of the unacceptability of the sample for toxin testing.
- Due to the sensitivity of the PCR test and the length of time it may continue to test positive, only one specimen will be tested per seven days if it tests negative, and one per 28 days if it tests positive.
NOTE: Physicians may request exception to this rule by contacting our Microbiology Department at 315-410-7067.