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
| Table 1. CT173-A - Antigen/Toxin or Toxin gene | Total | Grade |
|---|---|---|
| Negative / Negative | 43 | 8/8 |
| Negative/NT | 4 | 4/4 |
| NT / Negative | 9 | 4/4 |
| Total | 56 |
| Table 1. CT173-B - Antigen/Toxin or Toxin gene | Total | Grade |
|---|---|---|
| Positive / Positive | 47 | 8/8 |
| NT / Positive | 9 | 4/4 |
| Total | 56 |
| Table 2. CT173B - IC /PH Notification | Total | Grade |
|---|---|---|
| Yes | 50 | 4 |
| No | 5 | 0 |
| comment (only positives that are part of an outbreak are reportable to the MHO) | 1 | ungraded |
| Total | 56 |
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.
