Stool: Clostridium difficile common antigen and toxin/toxin gene
CT2011A: Positive/Positive CT2011B: Negative/Negative
CMPT QA/QC
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 gene Total Grade
positive/positive 47 Acceptable/Acceptable
not tested/positive 4 Ungraded/Acceptable
negative/negative 1 Unacceptable/Unacceptable
NT/Indeterminate* 1 Ungraded/Ungraded
NT/NT** 1 Ungraded/Ungraded
Total 54
**Lab has discontinued testing
Table 2. CT2011A - IC /PH Notification Total Grade
YES 50 Acceptable
NO (reported positive)*** 1 Ungraded
NO (reported neg or indeterminate) 2 Ungraded
No report (Not tested) 1 Ungraded
Total 54
*** PH authority does not require this lab to report for outpatients
Table 3. CT2011B - Antigen/Toxin or Toxin gene Total Grade
negative/negative 46 Acceptable/Acceptable
not tested/negative 5 Ungraded/Acceptable
negative/NT 1 Acceptable/Ungraded
positive/positive 1 Unacceptable/Unacceptable
NT/NT** 1 Ungraded/Ungraded
Total 54
**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.
