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Clostridium difficile

Item	Value
Test Update Information	On October 11, 2010 the Microbiology laboratory instituted a new testing algorithm for C. Difficile testing that utilizes an immunoassay to detect Somatic antigen/toxin with confirmatory PCR for Toxin B.
Approval req'd?	Yes, for repeat testing within 72 hours Testing for the 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 72 hours
Processing notes	Refrigerate sample
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 ≤ 2 hours, refrigerated ≤ 24 hours, frozen at -70C indefinite
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." 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	3/24/2013 7:29:17 PM
Entry Number	1149
Image caption	Testing Algorithm
Image

If you have additional questions regarding this test, please call: 415-353-1667