WESTGARD RULES 2.pptx

WESTGARD RULES

1. WESTGARD RULES

2. In 1981 Dr.James Westgard Of The University Of Wisconsin Published An Article On Laboratory Quality Control That Set The Basis For Evaluating Analytical Run Quality For Medical Laboratories . The Elements Of The Westgard Systems Are Based On Principles Of Statistical Process Control Used In Industry Nation Wide Since The 1950’s These Rules Are Used Individually Or In Combination To Evaluate The Quality Of Analytical Runs.

3. The rules of how to use LJ correctly has been described by James westgard and these are called Westgard rules. These rules are used for detecting changes in the analytical system.

4. Rules for what ? To decide whether an analytical run is in-control or out –of –control These rules can be applied as single rules and as a group of rules(multi-rules) Westgard rules can be applied only if your qc are plotted with the range of ±3 SD

5. Two key factors to keep in mind while selecting / using rules : Maximize error detection: Per cent error detection ( P ed ) >90% Minimize false rejection : Percent false rejection ( P fr ) < 5 %

6. 2 sets of QC rule nomenclatures N and L Within / across (run / material)

7. Nomenclature 1:

8. Nomenclature 2 : Within-run / across material DATE QC LEVELS DAY I Level 1 Level 2 DAY 2 Level 1 Level 2 Across run / same material DATE QC LEVELS DAY 1 LEVEL 1 LEVEL2 DAY 2 LEVEL 1 LEVEL 2 2/3 LEVEL OF QC IN THE SAME RUN SAME LEVEL (MATERIAL) OF QC BUT IN 2 OR MORE CONSECUTIVE RUNS

9. Gaussian curve

10. 1:2S RULE

11. 1:2S RULE One control exceeding the ± 2 SD limit. Denotes a random error / beginning of a systematic error Warning rule It can be both in plus and in minus direction Even In absence of any analytical errors 4.5 % of data points in the region of 1:2S region If only one level of QC is being run in the lab 1:2S has to be a rejection rule

12. 1:3S RULE

13. one control result has exceeded the established mean +/- 3SD range. Rejection rule a run is rejected when a single control measurement exceeds the mean 3SD control limit This rule identifies unacceptable Random error Beginning of a large systematic error .

14. 2:2s RULE two consecutive control results have exceeded the same mean +/- 2SD limit. Rejection rule. Identifies only systematic errors only There are two applications to this rule With-in-run ( in the 2 levels of QC in the same run) Across runs ( in the same QC in 2 consecutive runs )

15. 2:2s RULE

16. If a normal (level 1) and abnormal (level 2) control are >2s On the same side of mean: This run violates the within-run application for systematic error If level 1 is accepatable and level 2 is 1:2s, the level 2 result from previous run is examined: If level 2 in previous run was At +2.0s or greater Then the across run application for systematic error is violated

17. 2 of 3 2 s RULE: When 2 out of 3 control measurements exceed the same ±2SD control limit. Denotes systematic error.

18. R 4S RULE : When 2 control measurements in a group exceeds the mean ±2SD on either side or if the sum of SD of two material >4 SD Only be interpreted within-run, not across-run Identifies random error only Applied only within the current run .

19. R 4S RULE:

20. 3 1S RULE : 3 consecutive control meaurements exceed the same mean plus 1s or mean minus 1s control limit. Denotes systematic error 3 consecutive results Greater than 1s On the same side of mean Applied for within control material or across control material

21. 3 1S RULE :

22. Within control material violations indicate systematic bias in a single area of the method curve. While violation across control materials indicates systematic error over a broader concentration.

23. 4 1S RULE :

24. 10 x RULE The 10-x Control Rule indicates ten consecutive control results have fallen on the same side of the mean. rejection rule

25. 10 x RULE

26. When 6 or 8 or 9 or 10 or 12 control results on the same side of mean regardless of the specific SD in which they are located. Within control material violations indicate systematic bias in a single area of the method curve While violation across control materials indicates systematic error over a broader concentration .

27. 7 T RULE :

28. 7 T RULE :

29. RULE VIOLATION SYSTEMATIC ERROR RANDOM ERROR 1 : 2s 2 : 2s 1 : 3s 4: 1s 2 of 3:2s 3 : 1s 10x 7T R : 4s

30. Within run errors (The power of daily monitoring) Stop and take corrective action if a single point exceeds, 1 : 3s limit Stop and take corrective action if two levels of control exceed, 2:2s Stop and take corrective action, R4s limit . meant only to be applied within run.

31. Across run errors : ( the power of periodic review)

32. What do you do now ?

33. Corrective actions Things that can go wrong Instrument malfunction Reagents preparations,contamination , volume Tech error Control specimen is old or prepared improperly Corrective action Identify malfunction New reagents Identify error and repeat test Use new control

34. THANK YOU