CT173

Stool: Clostridium difficile common antigen and toxin/toxin gene

CT173A: Negative/Negative      CT173B: Positive/Positive     

Reference Laboratories

CT173-A: 12/12 laboratories reported either or both antigen/toxin or toxin gene negative

CT173-B: 12/12 labs reported either or both antigen/toxin or toxin gene positive

Participants’ results

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.

Maximum grade: CT173A: 8 , CT173B: 12

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.