How are C.diff. infection  cases best defined?

  1. To increase comparability between clinical settings, use available standardized case definitions for surveillance of (1) healthcare facility-onset (HO) CDI; (2) community-onset, healthcare facility–associated (CO-HCFA) CDI; and (3) community-associated (CA) CDI (good practice recommendation).

How is a C. diff. infection diagnosed?

Diagnosing a patient with C. diff. is done by obtaining a stool specimen.

  • This stool specimen has to be liquid in nature, and should take the shape of the cup.
  • The stool test will reveal the presence of toxins A & B produced by Clostridium difficile (C.diff) bacteria which can usually be detected in the stool sample.
  • There are many types of lab tests to make this diagnosis more rapid including enzyme immunoassay (EIA), polymerase chain reaction (PCR), and tissue culture assay.

There are laboratories that use both the EIA test and the tissue assay testing to ensure accurate results. There are also many laboratories that only use the PCR testing.  There are many positive and negative attributes as they carry different percentages in regards to sensitivity/specificity, but it is important to know what you are testing for when diagnosing.

For example, the PCR is detecting for the gene that encodes for the toxin, whereas the EIA and assays are looking at the presence of the toxin. Regardless of which test is used, it is important to determine if the patient has had 3 or more watery stools within 24 hours without any underlying precepting reason i.e. laxatives, chronic diarrhea,   Any of these tests coupled with watery diarrhea is the true diagnosis of C. diff. infection  also known as a CDI (clostridium difficile infection).

In combination with the above testing, a physician may order a sigmoidoscopy to look for areas of inflammation and pseudomembranes in the lower colon. When there are concerns of complications of CDI, a CT scan may be ordered to check for thickening of the walls of the colon associated with pseudomembranous colitis.

What is the preferred population for C. difficile testing, and should efforts be made to achieve this target?

  1. Patients with unexplained and new-onset 3 or more unformed stools in 24 hours are the preferred target population for testing for CDI (weak recommendation, very low quality of evidence).

What is the best-performing method (ie, in use positive and negative predictive value) for detecting patients at increased risk for clinically significant C. difficile infection in commonly submitted stool specimens?

  1. Use a stool toxin test as part of a multistep algorithm (ie, glutamate dehydrogenase [GDH] plus toxin; GDH plus toxin, arbitrated by nucleic acid amplification test [NAAT]; or NAAT plus toxin) rather than a NAAT alone for all specimens received in the clinical laboratory when there are no preagreed institutional criteria for patient stool submission (Figure 2) (weak recommendation, low quality of evidence).
Figure 2.

Clostridium difficile infection laboratory test recommendations based on preagreed institutional criteria for patient stool submission. Abbreviations: CDI, Clostridium difficile infection; EIA, enzyme immunoassay; GDH, glutamate dehydrogenase; NAAT, nucleic acid amplification test.

What is the most sensitive method of diagnosis of CDI in stool specimens from patients likely to have CDI based on clinical symptoms?

  1. Use a NAAT alone or a multistep algorithm for testing (ie, GDH plus toxin; GDH plus toxin, arbitrated by NAAT; or NAAT plus toxin) rather than a toxin test alone when there are preagreed institutional criteria for patient stool submission (Figure 2) (weak recommendation, low quality of evidence).

What is the role of repeat testing, if any? Are there asymptomatic patients in whom repeat testing should be allowed, including test of cure?

  1. Do not perform repeat testing (within 7 days) during the same episode of diarrhea and do not test stool from asymptomatic patients, except for epidemiological studies (strong recommendation, moderate quality of evidence).

Does detection of fecal lactoferrin or another biologic marker improve the diagnosis of CDI over and above the detection of toxigenic C. difficile Can such a subset predict a more ill cohort?

  1. There are insufficient data to recommend use of biologic markers as an adjunct to diagnosis (no recommendation).



When should a neonate or infant be tested for C. difficile?

  1. Because of the high prevalence of asymptomatic carriage of toxigenic C. difficile in infants, testing for CDI should never be routinely recommended for neonates or infants ≤12 months of age with diarrhea (strong recommendation, moderate quality of evidence).

When should a toddler or older child be tested for C. difficile?

  1. Clostridium difficile testing should not be routinely performed in children with diarrhea who are 1–2 years of age unless other infectious or noninfectious causes have been excluded (weak recommendation, low quality of evidence).
  2. In children ≥2 years of age, C. difficile testing is recommended for patients with prolonged or worsening diarrhea and risk factors (eg, underlying inflammatory bowel disease or immunocompromising conditions) or relevant exposures (eg, contact with the healthcare system or recent antibiotics) (weak recommendation, moderate quality of evidence).

More information can be found at: