Clostridioides difficile Infection (CDI) Surveillance

Incident case

When the following criteria are met for a patient who lives in the surveillance area:

• A patient with a positive C. difficile toxin assay or a positive C. difficile molecular assay (e.g., PCR) performed on a stool specimen, without a positive specimen in the prior 8 weeks.
  • Patient must be at least 1 year old.
  • For surveillance purposes, an individual may be classified and captured as a new incident case if 8 consecutive weeks have elapsed since their last C. difficile-positive test.

Recurrent episodes

• Patients with a positive C. difficile stool specimen between 2 and 8 weeks of the last positive specimen.

Duplicate episodes

• Patients with a positive C. difficile stool specimen less than 2 weeks since the last positive specimen.

EIP site staff identify cases based on reports of positive C. difficile toxin assays or C. difficile nucleic acid amplification assays from clinical, reference and commercial laboratories serving residents of the surveillance areas.

EIP site staff record information on additional positive specimens from the same patient to identify and track recurrent or duplicate episodes, as well as new cases.

To determine epidemiologic class, EIP site staff perform a brief medical record review of all* incident CDI cases to collect the following data:

• Basic demographic characteristics.
• Location of stool collection.
• Healthcare exposures.

EIP site staff do not review records of recurrent or duplicate episodes.

*In Colorado and Georgia (the EIP sites with the largest surveillance populations), EIP site staff review a random sample of incident cases.

1. Healthcare facility-onset (HCFO) if the positive stool specimen collected is either:
   1. Greater than three calendar days after hospital admission.
   2. In a resident of a long-term care facility.
2. Community-onset healthcare facility-associated (CO-HCFA) if the positive stool specimen collected is:
   1. Either in an outpatient setting or within 3 calendar days after hospital admission.
   2. In a person with documented overnight stay in a healthcare facility (i.e., hospitalization or long-term care facility stay) in the 12 weeks before stool specimen collection.
3. Community–associated (CA) if positive stool specimen collected is:
   1. Either in an outpatient setting or within 3 calendar days after hospital admission.
   2. In a person with no documented overnight stay in a healthcare facility during the 12 weeks before the specimen collection.

A portion of cases subsequently undergo a comprehensive medical record review for clinical information and relevant risk factors.

Laboratory characterization

EIP site staff collect a convenience sample of stool specimens from incident CDI cases for whom case report forms have been completed. Stool specimens are sent to reference laboratories for culture. C. difficile isolates obtained from these cultures are sent to CDC for molecular typing and characterization.