C. difficile Diagnostic Testing

Diagnostic Performance and Recommendations

The Infectious Diseases Society of America recommends that perirectal swabs can be used as an alternative to stool specimens for C. difficile testing in patients with suspected severe C. difficile infection complicated by ileus who are unable to produce stool specimens, with excellent diagnostic performance 1, 2
Perirectal swab testing by PCR demonstrates 95.7% sensitivity, 100% specificity, 100% positive predictive value, and 99.1% negative predictive value compared to stool testing in patients with ileus 1, 2
The American College of Physicians recommends that diagnostic testing should be performed only on unformed stool samples from symptomatic patients as the standard approach, with testing limited to patients with ≥3 unformed stools in 24 hours with no obvious alternative explanation 3, 5
Stool specimens remain the gold standard sample type for C. difficile testing in most clinical scenarios, according to the Infectious Diseases Society of America 3, 6, 7
Testing formed stool can result in false positive results and unnecessary antibiotic therapy, as stated by the World Journal of Emergency Surgery 1, 2
Clinical context including recent antibiotic exposure, hospitalization history, fever, abdominal pain, and leukocytosis should guide interpretation of results, as recommended by the Infectious Diseases Society of America 1, 4

The Society for Healthcare Epidemiology of America recommends that when perirectal swabs are used in appropriate patients (those with ileus), they should be tested using the same multi-step algorithms recommended for stool specimens, including NAAT alone or a multistep algorithm (GDH plus toxin; GDH plus toxin arbitrated by NAAT; or NAAT plus toxin) 5
The Infectious Diseases Society of America recommends that without pre-agreed criteria, a stool toxin test should be used as part of a multistep algorithm rather than NAAT alone 5