Handouts Quality Control and Quality Assurance for Antibiotic Testing

8/8/2019 Handouts Quality Control and Quality Assurance for Antibiotic Testing

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date zone size (mm)

23-Jan-10 23

24-Jan-10 27

25-Jan-10 26

26-Jan-10 25

27-Jan-10 25

28-Jan-10 24

29-Jan-10 24

30-Jan-10 26

31-Jan-10 271-Feb-10 29

2-Feb-10 29

3-Feb-10 23

4-Feb-10 23

5-Feb-10 22

6-Feb-10 23

7-Feb-10 238-Feb-10 22

9-Feb-10 22

10-Feb-10 23

11-Feb-10 23

12-Feb-10 22

date zone size (mm)

1-Jan-10 25

2-Jan-10 243-Jan-10 25

4-Jan-10 24

5-Jan-10 26

6-Jan-10 24

7-Jan-10 27

8-Jan-10 25

9-Jan-10 2610-Jan-10 27

11-Jan-10 27

12-Jan-10 26

13-Jan-10 28

14-Jan-10 23

15-Jan-10 24

16-Jan-10 27

17-Jan-10 26

18-Jan-10 26

19-Jan-10 28

20-Jan-10 25

21-Jan-10 25

22-Jan-10 24

Quiz: anything unusual about

QC zone sizes? QC ATCC

25923 (Saureus) with

Cefoxitin disc

(FOX)

CLSI: zone size

within 22-29mm


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Quality Control and QualityAssurance for Antibiotic Testing

22 Sep 2010

Microbiology Technical Workshop


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Introduction

Various standards

eg CLSI, CDS

Various methods

Eg disc susceptibility, microbroth dilution Follow QC instructions as stated


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Introduction (2)

Some general principles apply:

1. Materials and Procedures : strictly adhere to2. Able to detect abnormalities and take

necessary corrective actions


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Materials & Procedures

General: Expiry date & storage

conditions manufacturersrecommendation

1. Media:

sterility

Support growth

Does not interfere with activity of antibiotics


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Materials & Procedures (3)

Perform and interpret correctly

Technologists : adequately trained


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Detect Errors / Corrective actions

Documentation

Useful for monitoring / troubleshooting futureQC failures

CAP requirements


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What to do when QC is out

CLSI recommendations:

ID cause

Cause found repeat x 01

Repeat ok = case close

Repeat out of range repeat

No obvious

cause

5 consecutive days

All within range= case close

1 out ofrange

Re-examine


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Common sources of error

Media Storage

Thickness

Contamination

pH

Wrong media

Antibiotics

Storage Wrong disc

QC strains Wrong strains

Inoculum

Storage

Contamination

Old cultures

Procedures

Incubation conditions Disc placement

transcription


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Other Tools

Control charts and Westgard rules

CUSUM


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date zone size (mm)

b


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Control Chart ATCC 25923 SAU with FOX

20

21

22

23

24

25

26

27

28

29

30

1-Ja

n-1

0

3-Ja

n-1

0

5-Ja

n-1

0

7-Ja

n-1

0

9-Ja

n-1

0

11-Jan-1

0

13-Jan-1

0

15-Jan-1

0

17-Jan-1

0

19-Jan-1

0

21-Jan-1

0

23-Jan-1

0

25-Jan-1

0

27-Jan-1

0

29-Jan-1

0

31-Jan-1

0

2-Feb-1

0

4-Feb-1

0

6-Feb-1

0

8-Feb-1

0

10-Feb-1

0

12-Feb-1

0

date

1-Feb-10 29

2-Feb-10 29

3-Feb-10 23

4-Feb-10 23

5-Feb-10 22

6-Feb-10 23

7-Feb-10 238-Feb-10 22

9-Feb-10 22

10-Feb-10 23

11-Feb-10 23

12-Feb-10 22


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Warning rules

Warning 11112SD2SD2SD2SD : It is violated if the IQC value exceeds the

mean by 2SD. It is an event likely to occur normally in less

than 5% of cases.

Warning 22222SD2SD2SD2SD : It detects systematic errors and is violatedwhen two consecutive IQC values exceed the mean on the

same side of the mean by 2SD.

Warning 44441SD1SD1SD1SD : It is violated if four consecutive IQC valuesexceed the same limit (mean 1SD) and this may indicate the

need to perform instrument maintenance or reagent

calibration.


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Mandatory rules

Mandatory 11113SD3SD3SD3SD : It is violated when the IQC value exceeds

the mean by 3SD. The assay run is regarded as out of

control.

Mandatory RRRR4SD4SD4SD4SD : It is only applied when the IQC is tested induplicate. This rule is violated when the difference in SD

between the duplicates exceeds 4SD.

Mandatory 10x10x10x10x : This rule is violated when the last 10consecutive IQC values are on the same side of the mean or

target value.


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Scenario 1

New lot / new antibiotics

How frequently should you QC?


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Scenario 2

Check

Media Antibiotics

QC organism Procedure


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Scenario 1

New antibiotic introduced

CLSI Test for 30 consecutive days

If no more 3 (out of 30) are outsideacceptable range - convert to weekly testing


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Scenario 2

7 Oct 2009 - QC ATM 20mm (expected

23-29mm) What would you do?


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Scenario 2

Repeat testing performed by same staff

Correct QC organism, media, procedure,incubation, interpretation

Wrong inoculum - too heavy


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Scenario 3

14 Oct 2008

Vitek Gram positive panel QC Multiple drugs MIC - resistant

Expected - sensitive


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Scenario 3

Purity plate - contaminated with other

organisms


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Scenario 4

QC Vitek Gram positive panel

Multiple antibiotics - resistant Expected - sensitive


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Scenario 4

Test repeated

With organism from purity plate (prev run)- resistant

And separate set from weekly QC plate -sensitive

Wrong ATCC used.


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Quality assurance

Education

External Proficiency test, eg CAP Literature and publications

Accreditation

Handouts Quality Control and Quality Assurance for Antibiotic Testing

Documents

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