Westgard rules

To assure that our tests results are correct, we run control materials. Based on the control material , we decide whether our results are acceptable.

What is Multirule QC? “Multirule QC uses a combination of decision criteria, or control rules, to decide whether an analytical run is in-control or out-of-control” In-control = acceptable Out-of-control= unacceptable “The advantages of multirule QC procedures are that false rejection can be kept low while at the same time maintaining high error detection.”

Westgard rules The formulation of Westgard rules were based on statistical methods. Westgard rules are commonly used to analyse data in Shewhart control charts. Westgard rules are used to define specific performance limits for a particular assay and can be used to detect both random and systematic errors.

Mean & Standard deviation Mean= the average of the numbers: a calculated "central" value of a set of numbers. To calculate: Just add up all the numbers, then divide by how many numbers there are. Standard deviation = quantity expressing by how much the members of a group differ from the mean value for the group

6 Basic Rules

How do you perform multirule QC? 1-collect your control measurements 2- Find mean and Standard deviation 3- Draw (+3, +2 +1 , 0 , -1 , -2 , -3) lines on the Levey-Jennings chart

12s Rule 1= one point 2S= position exceeds 2S “12srefers to the control rule that is commonly used with a Levey-Jennings chart when the control limits are set as the mean plus/minus 2s. In the original Westgard multirule QC procedure, this rule is used as a warning rule to trigger careful inspection of the control data by the following rejection rules. ”

12s Rule

13sRule “13s refers to a control rule that is commonly used with a Levey-Jennings chart when the control limits are set as the mean plus 3s and the mean minus 3s. A run is rejected when a single control measurement exceeds the mean plus 3s or the mean minus 3s control limit”

22s Rule “22s reject when 2 consecutive control measurements exceed the same mean plus 2s or the same mean minus 2s control limit.”

41s Rule “41s - reject when 4 consecutive control measurements exceed the same mean plus 1s or the same mean minus 1s control limit.”

R4s Rule “R4s - reject when 1 control measurement in a group exceeds the mean plus 2s and another exceeds the mean minus 2s. The graphic below should really imply that points 5 and 6 are within the same run.”

8x ,10x , 12x Rule reject when 8 , 10 or 12 consecutive control measurements fall on one side of the mean.

10x Rule

8x Rule

12x Rule

SUMMARY Westgard rules are used to know whether to accept or reject the run. If one point exceeds 2s control limit (12s) Look carefully but no stop require ( accept run) Look carefully means is there any of the other rules in the graph Stop required ( reject run) for 13s , 22s , R4s , 41s 8x ,10x , 12x Rules

Reference https://www.westgard.com/mltirule.htm