Stool: Clostridium difficile common antigen and toxin/toxin gene

CT2011A: Positive/Positive     CT2011B: Negative/Negative


CT2011-A: C.difficile common antigen positive and gene/toxin positive, viable for 40 days

CT2011-B: C.difficile common antigen negative and gene/toxin negative, viable for 40 days

Reference Laboratories

CT-A: 9 laboratories reported positive antigen and positive toxin/toxin gene; 2 reported only toxin/toxin gene positive

CT-B: 8 laboratories reported both antigen and toxin negative; one lab each reported only antigen or toxin negative.

Participants’ results

NOTE: grading for Clostridium difficile toxin testing has changed. Please click here for more details

Table 1. CT2011A - Antigen/Toxin or Toxin geneTotalGrade
not tested/positive4Ungraded/Acceptable

**Lab has discontinued testing

Table 2. CT2011A - IC /PH NotificationTotalGrade
NO (reported positive)***1Ungraded
NO (reported neg or indeterminate)2Ungraded
No report (Not tested)1Ungraded

*** PH authority does not require this lab to report for outpatients


Table 3. CT2011B - Antigen/Toxin or Toxin geneTotalGrade
not tested/negative 5Ungraded/Acceptable

**Lab has discontinued testing

NT: not tested

Suitability for Grading

A challenge is considered suitable for grading if agreement is reached by 80 percent of selected reference group and at least 70 percent of the participants.

Antigen and toxin detection was correctly performed by at least 80 percent of reference laboratories and greater than 70 percent of all laboratories thus, both challenges were determined to be suitable for grading.

Grading: Please note that grading for Clostridium difficile toxin testing has changed. Please click here for more details

The samples are assessed for homogeneity and stability using in-house quality control methods and random selection of samples before and during production, and post sample delivery. The number of random samples selected is based on selection tables within Military standard 105E (1).

The challenge sample lot was confirmed to be homogeneous and stable for at least 15 days.

Grading of Clostridium difficile common antigen and toxin/toxin gene detection is based on a Positive / Negative result, no further statistical analysis is performed on the results beyond that described under “Suitability for grading(1) Famum NR. Acceptance sampling. In: Modern Statistical Quality Control and Improvement. Belmont, California.: Duxbury Press; 1994:305.

Posted in Clostridium difficile Results, critiques