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Clostridium difficile

Item Value
Approval req'd? Contact microbiology lab to obtain approval for repeat testing within 7 days.

Contact Pediatric Infectious Disease to obtain approval to do testing on patient's <1 year old.

Testing for NAP1 epidemic strain of C. difficile is available with Infectious Disease approval.
Available Stat? No
Test code P328
Test group Clostridium difficile
Performed by Microbiology
In House Availability
Weekdays Day & Evening shift
Weekends Day shift only
Method Rapid membrane EIA +/- PCR
Collection Instructions Potentially interfering substances include Vagisil cream and zinc oxide paste.

If C. difficile is clinically suspected in a patient with ileus, a rectal swab may be submitted. The swab should be visibly soiled with stool and submitted in a clean container.
Container type Urine cup
Amount to Collect 2 ml stool
Sample type Unformed stool

If C. difficile is clinically suspected in a patient with ileus, a rectal swab may be submitted. The swab should be visibly soiled with stool and submitted in a clean container.
Preferred volume 2 mL stool
Min. Volume 1 mL stool
UCSF Rejection Criteria Formed stool. Stool in preservative. More than one sample in 7 days Samples on patients <1 year old.
Processing notes Samples from children <1 year old: TND as CONSUL and add code CDPED C. difficile testing not performed on children <12 month old unless prior approval obtained from Pediatric ID Service
Normal range Negative for C. difficile
Critical value First sample positive for C. difficile toxin on an inpatient or ED patient
Synonyms Clostridium difficile Ag; Enterocolitis; Pseudomembranous enterocolitis; Clostridium difficile toxin; enterotoxin; CDI
Stability Room temperature 1 day, refrigerated 3 days
Turn around times Same or next day
Reflex? PCR for toxin will be performed, and billed separately, when the rapid membrane EIA is positive for only GDH antigen or only toxin.
Additional information Asymptomatic carriage is common, so only symptomatic patients should be tested. Submit stools from patients with diarrhea ONLY (≥ 3 unformed stools in ≤ 24 hours, stool must conform to shape of container). Patients with ileus will also be tested - note this in Apex. Most patients with clinical C. difficile associated diarrhea have had prior antimicrobial therapy."

Due to high rates of colonization in children, C. difficile testing will not be performed on children < 12 months old unless prior approval is obtained from pediatric infectious disease service.

Stools samples are screened for bacterial glutamate dehydrogenase (GDH) somatic antigen, along with an immunoassay for toxin. Stools with one positive result for GDH antigen or toxin will be tested by PCR.

Negative results are reported as NEGATIVE toxin assay. NEGATIVE somatic antigen assay. (Interpretation: NEGATIVE TEST)

A positive somatic antigen result indicates the presence of this organism in the fecal specimen. A positive somatic antigen result is accompanied by the toxin result as either:
NEGATIVE toxin assay. Positive somatic antigen assay.(Interpretation: NEGATIVE TEST, not consistent with C. difficile induced disease.) or POSITIVE toxin assay. POSITIVE somatic antigen assay. (Interpretation: POSITIVE TEST consistent with C. difficile induced disease.)

If C. difficile is clinically suspected in a patient with ileus, a rectal swab may be submitted. The swab should be visibly soiled with stool and submitted in a clean container.

Testing for the NAP1 epidemic strain of C. difficile is available with Infectious Disease approval.
CPT coding Rapid membrane EIA: 87324, 87449
PCR: 87493
LOINC code 31308-0
Last Updated 5/31/2016 9:52:34 PM
Entry Number 1149
Image caption Testing Algorithm
Image see image caption
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