Stool: Clostridium difficile common antigen and toxin/toxin gene – Shipped May 09, 2017
CT171A: Positive/Positive CT171B: Positive/Positive .
Reference Laboratories
CT171A: 12/12 laboratories reported C.difficile common antigen/gene/toxin positive/positive or not tested/positive
CT171B: 12/12 laboratories reported C.difficile common antigen/gene/toxin positive/positive or not tested/positive
Participants’ results
| Table 1. CT171-A - Antigen/Toxin or Toxin gene | Total | Grade |
|---|---|---|
| Positive / Positive | 44 | 8/8 |
| NT / Positive | 9 | 4/4 |
| Indeterminate / Negative (1) | 1 | 0/4 |
| Positive / Negative (2) | 1 | 4/8 |
| Total | 55 |
| Table 2. CT171A - IC /PH Notification | Total | Grade |
|---|---|---|
| Yes | 47 | 4 |
| No | 6 | 0 |
| n/a | 2 | ungraded |
| Total | 55 |
| Table 3. CT171-B - Antigen/Toxin or Toxin gene | Total | Grade |
|---|---|---|
| Positive / Positive | 43 | 8/8 |
| NT / Positive | 9 | 4/4 |
| No Report / Positive | 1 | 4/4 |
| Indeterminate / Negative (1) | 1 | 0/4 |
| Positive / Negative (2) | 1 | 4/8 |
| Total | 55 |
| Table 4. CT171B - IC /PH Notification | Total | Grade |
|---|---|---|
| Yes | 46 | 4 |
| No | 7 | 0 |
| n/a | 2 | ungraded |
| Total | 55 |
NT: not tested; (1) Ag positive/tox negative, QC visible; Referred for further testing; (2) Unable to confirm presence of Clostridium difficile toxin. Referred sample for Toxin PCR testing.
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: CT171A: 12 , CT171B: 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.
