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VIDAS LPT - Summary 2012
EUROFINS IPL Nord SAS
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1 rue du Professeur Calmette
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59046 LILLE cedex
p 2/14
CONTENT
1
Introduction ........................................................................................................................................................... 3
1.1
Validation reference ..................................................................................................................................... 3
1.2
VIDAS
®
UP Listeria method: Principle and protocol .................................................................................... 3
1.2.1
VIDAS® UP Listeria principle .................................................................................................................. 3
1.2.2
General protocol ...................................................................................................................................... 3
1.2.3
Specific protocol for surface samples ...................................................................................................... 4
1.2.4
Confirmation of positive results................................................................................................................ 4
1.3
Scope ........................................................................................................................................................... 4
1.4
Reference method ....................................................................................................................................... 5
2
Comparative study of methods............................................................................................................................. 5
2.1
Relative accuracy, relative specificity and relative sensibility...................................................................... 5
2.1.1
Number and nature of samples ............................................................................................................... 5
2.1.2
Artificial samples contamination .............................................................................................................. 5
2.1.3
Relative accuracy (AC), relative specificity (SP) and sensitivity (SE) calculations.................................. 6
2.1.4
Analysis of discrepant results .................................................................................................................. 6
2.1.5
Comments on confirmations .................................................................................................................... 7
2.1.6
Comments on results obtained after storage at 2-8°C ............................................................................ 7
2.2
Relative detection level ................................................................................................................................ 7
2.3
Inclusivity and exclusivity............................................................................................................................. 7
3
Inter-laboratory study............................................................................................................................................ 8
3.2
Experimental parameter tests...................................................................................................................... 8
3.2.1
Levels obtained after artificial contamination........................................................................................... 8
3.2.2
Temperature recorded (transport, receipt) and reception times .............................................................. 8
3.2.3
Conclusion ............................................................................................................................................... 9
3.3
Results of analyses...................................................................................................................................... 9
3.3.1
Total viable count..................................................................................................................................... 9
3.3.2
Results obtained by collaborating laboratories ........................................................................................ 9
3.3.3
Comments (discrepancies with respect to expected results, exclusions, etc.)...................................... 10
3.4
Calculation ................................................................................................................................................. 10
3.4.1
Specificity (%SP) and sensitivity (%SE) for both methods .................................................................... 10
3.4.2
Relative accuracy (AC) .......................................................................................................................... 10
3.4.3
Study of discrepant results .................................................................................................................... 11
3.5
Interpretation.............................................................................................................................................. 11
3.5.1
Comparison of relative accuracy (AC), specificity (SP) and sensitivity (SE) values ............................. 11
3.5.2
Accordance (DA).................................................................................................................................... 11
3.5.3
Concordance (COR) .............................................................................................................................. 12
3.5.4
Odds Ratio (COR).................................................................................................................................. 12
4
Practicability ....................................................................................................................................................... 12
5
General conclusion............................................................................................................................................. 14