What are the key diagnostic criteria for confirming a Clostridium difficile infection in a patient presenting with diarrhea?

Confirming a Clostridioides difficile infection (CDI) in a patient presenting with diarrhoea primarily relies on a positive C. difficile toxin test ¹. However, this test result must be interpreted in conjunction with strong clinical suspicion ¹.

It is important to note that C. difficile may be an incidental finding in the stools of people with diarrhoea caused by other factors, and indiscriminate testing increases the likelihood of a false-positive result ¹. Colonisation with C. difficile is common, and individuals who are colonised may be asymptomatic ¹ (Winslow, 2014; Ong, 2017; McDonald, 2018).

If a patient has a negative C. difficile toxin test result but there is a strong clinical suspicion of CDI, or if there is doubt, it is advisable to consider seeking specialist advice and potentially retesting ¹. North American guidelines also recommend considering repeat testing in symptomatic individuals with a negative result if there is a high clinical suspicion of CDI ¹ (McDonald, 2018). This approach is consistent with European guidelines and Public Health England advice, which acknowledge that a single negative result can occur ¹ (Crobach, 2016; PHE, 2018).