Stool: Clostridium difficile common antigen and toxin/toxin gene
CT1911A: negative/negative CT1911B: positive/positive
CT1911-A: C.difficile common antigen negative and gene/toxin negative, viable for 40 days
CT1911-B: C.difficile common antigen positive and gene/toxin positive, viable for 40 days
CT1911-A: 9/12 labs reported common Antigen/Toxin or Toxin gene negative/negative, 3 labs reported not tested/negative
CT1911-B: 9/12 labs reported common Antigen/Toxin or Toxin gene positive/positive, 3 labs reported not tested/positive
NOTE: grading for Clostridium difficile toxin testing has changed. Please click here for more details
Table 1. CT1911A - Antigen/Toxin or Toxin gene Total Grade
negative/negative 47 Acceptable/Acceptable
not tested/negative or negative/not tested 8 Ungraded/Acceptable or Acceptable/Ungraded
positive/positive 2 Unacceptable/Unacceptable
Total 57 Table 3. CT1905B - Antigen/Toxin or Toxin gene Total Grade
positive/positive 50 Acceptable/Acceptable
not tested/positive 5 Ungraded/Acceptable
negative/negative 2 Unacceptable/Unacceptable
Total 57 Table 4. CT1905B - IC /PH Notification Total Grade
Yes 54 Acceptable
No 3 Unacceptable
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 40 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.