Stool: Clostridium difficile common antigen and toxin/toxin gene
CT2105A: Positive/Positive CT2105B: Positive/Positive
CMPT QA/QC
CT2105-A: C.difficile common antigen positive and gene/toxin positive, viable for 60 days
CT2105-B: C.difficile common antigen positive and gene/toxin positive, viable for 60 days
Reference Laboratories
CT2105-A: 9/11 labs reported both antigen and toxin positive; one lab did not test antigen but reported toxin positive; one lab did not test antigen and reported toxin negative
CT2105-B: 9/11 labs reported both antigen and toxin positive; two labs did not test antigen but reported toxin positive
Participants’ results
NOTE: grading for Clostridium difficile toxin testing has changed. Please click here for more details
Table 1. CT2105A - Antigen/Toxin or Toxin gene Total Grade
positive/positive 48 Acceptable/Acceptable
not tested/positive 4 Ungraded/Acceptable
not tested/negative 1 Ungraded/Unacceptable
not tested/not tested* 2 Ungraded/Ungraded
No report/No report 1 Unacceptable/Unacceptable
Total 56
*Labs could not process samples because of specific incidents.
Table 2. CT2105A - IC /PH Notification Total Grade
YES 50 Acceptable
NO (reported positive) 1 Unacceptable
NO (reported positive)** 1 Ungraded
Not applicable (reported negative, no reported) 4 Ungraded
Total 56
**PH authority does not require this lab to report to infection control for outpatients
Table 1. CT2105B - Antigen/Toxin or Toxin gene Total Grade
positive/positive 48 Acceptable/Acceptable
not tested/positive 5 Ungraded/Acceptable
not tested/not tested* 2 Ungraded/Ungraded
no report/no report 1 Unacceptable/Unacceptable
Total 56
*Labs could not process samples because of specific incidents.
Table 2. CT2105B - IC /PH Notification Total Grade
YES 51 Acceptable
NO (reported positive) 1 Unacceptable
NO (reported positive)** 1 Ungraded
Not applicable (not tested/no report) 3 Ungraded
Total 56
**PH authority does not require this lab to report to infection control for outpatients
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 60 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.
