Clostridium difficile – misconceptions about testing

Confine testing to symptomatic patients. Testing of patients with formed stools may generate false positives due to asymptomatic carriage of toxigenic strains. An unfortunate side effect of multiplex PCR stool assays, are that tests that are inappropriate to the clinical circumstance may be performed, generating false positives.

Also test at-risk (i.e. antibiotic or ppi-exposed) symptomatic patients from the communityrecent Australian data showed up to 26% of diagnoses of CDI occurred in patients who have had no contact with healthcare.

Avoid re-testing CDI patients post recovery – persistent carriage of the toxigenic organism is the norm despite treatment.  A recovered patient may remain positive for at least one month.

Patients with C. difficile generally do not go under the radar, although there are well-documented cases of severe C. difficile that only get recognised post mortem (for instance, severe C. difficile may be associated with an ileus and/or sepsis and significant enteritis may not get considered).

For a consideration of advised ANZ laboratory testing practice for CDI, see this Pathology 2011 reference or this more recent review.

CDI= C. difficile infection  PPI = proton pump inhibitor drug, also a risk factor for CDI

Image from



  1. Christina VAndenbroucke-Grauls · · Reply

    Thanks for this excellent list of misconceptions. Fully agree!
    I was wondering where the figure comes from and on what data the 30-36 hours effects are based? As far as I am aware of, time interval between acquisition and development of disease is not known?


    1. Hi- the graphic described data obtained from a mouse experiment. Agree no similar data from humans! regards John


  2. […] C. difficile infections are particularly associated with broad spectrum antibiotics. Appropriate diagnosis is important. Current treatment guidelines recommend repeat treatment with antibiotics in order to […]


  3. […] information is also available in our previous posts on C. difficile testing and faecal microbiota […]


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