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CT163

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Stool: Clostridium difficile common antigen and toxin/toxin gene – Shipped November 07, 2016

CT163A: Positive/Positive      CT163B: Negative/Negative

Reference Laboratories

CT163A: 12/12 laboratories reported C.difficile common antigen/gene/toxin positive/positive or not tested/positive

CT163B: 12/12 laboratories reported C.difficile common antigen/gene/toxin negative/negative, negative/not tested or not tested/negative

Participants’ results

Table 1. CT163-A - Antigen/Toxin or Toxin geneTotalGrade
Positive / Positive468/8
Not tested/Positive94/4
Total55

Table 2. CT163A - IC /PH NotificationTotalGrade
Yes484/4
No report60/4
n/a (PH lab does not report directly to IC)1ungraded
Total55

Table 3. CT163-B - Antigen/Toxin or Toxin geneTotalGrade
Negative / Negative418/8
Negative / Not tested54/4
Not tested / Negative64/4
Total 55

PH: Public Health; IC: infection control

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: CT163A: 12 , CT163B: 8

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.

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