Does the handling time of unrefrigerated human fecal specimens impact the detection of Clostridium difficile toxins in a hospital setting?

BACKGROUND The stability of Clostridium difficile toxins is an important factor in determining the accuracy of the enzyme immunoassay (EIA). The Centers for Disease Control has stated that C. difficile toxins may become undetectable in unrefrigerated stool specimens within 2 h after collection. PURPOSE The purpose of our study was to determine how the unrefrigerated handling time of human fecal specimens affects the results of C. difficile infection (CDI) testing. METHODS A retrospective review of CDI testing with Premier™ Toxins A and B kit was conducted in northern New Jersey, USA. Stool collection times and receiving times were recorded for each specimen. The unrefrigerated handling time was calculated for each. RESULTS A total of 1126 fecal specimens were submitted. We excluded 72 fecal specimens due to incomplete documentation. We included 1054 fecal specimens collected from 636 hospitalized patients. A total of 132 out of 1054 specimens (12.5%) tested positive for C. difficile toxins. Nine hundred and fifty-four specimens were unrefrigerated for 13 h or less, of which 127 (13.3%) tested positive. Five (5%) of the 100 specimens that were unrefrigerated for more than 13 h tested positive (p = 0.02). CONCLUSION C. difficile toxins can still be detected up to 13 h after collection in unrefrigerated human fecal specimens. However, fecal specimens should be processed according to the current recommendations to ensure the reliability of EIA testing until the results of our study are confirmed with prospective studies.