Pro50-10 Guide Westgard Rules PDF

Preview

Summary

Download Pro50-10 Guide Westgard Rules PDF

Description

SMILE Johns Hopkins University Baltimore, MD USA Guideline Number Westgard Rules - Guidelines Effective Date Author Heidi Hanes Subject Page Westgard Rules Guidelines

Pro50-10-G 12/18/06 1 of 2

SMILE Comments: This document is provided as an example only. It must be revised to accurately reflect your lab’s specific processes and/or specific protocol requirements. Users are directed to countercheck facts when considering their use in other applications. If you have any questions contact SMILE.

What are Westgard Rules? Westgard Rules are multirule QC rules to help analyze whether or not an analytical run is in-control or outof-control. It uses a combination of decision criteria, usually 5 different control rules to judge the acceptability of an analytical run. Westgard Rules are generally used with 2 or 4 control measurements per run, which means they are appropriate when two different control materials are measured 1 or 2 times per material, which is the case in many chemistries application. For hematology, coagulations, and immunoassays applications some alternate control rules are more suitable when three control materials are analyzed.

Explanation of Individual Rules 12s One control measurement exceeding 2 standard deviations of control limits either above or below the mean. This rule is used a warning rule to trigger careful inspection of the control data. 13s This rule is commonly used with a Levey-Jennings chart when the control limits are set as the mean +3 standard deviations of control limits. A run is rejected when a single control measurement exceeds the mean +3 control limits. 22s The control run is rejected with 2 consecutive control measurements 2 standard deviations of control limits on the same side of mean with this rule. R4s This rule rejects a run if two control measurements in a group exceed the mean with a 4 standard deviation difference between the 2 controls 41s This rule rejects a run with the 4th consecutive control measurement exceeding 1 standard deviation on the same side of the mean. 10x This rule rejects a control run when there are 10 consecutive controls on the same side of the mean.

How to perform multirule QC To perform multirule QC collect your control measurements in the same way as you would for a regular Levey-Jennings control chart; establish means and standard deviations for the control materials; then create a Levey-Jennings chart with the mean +3, +2, and +1 standard deviations. The only difference is the interpretation of the data.

681257b51af72a5dbff337326c8378cb.doc

Ver 1.0

5/2/2021

SMILE Johns Hopkins University Baltimore, MD USA The 12s rule is used as a warning to trigger application of the other rules. Any time a single measurement exceeds a 2 standard deviation control limit, you respond by inspecting the control data using the other rules. This doesn’t mean stop, it just means to look carefully at the data before proceeding.

By using the following diagram you should be able to decide what if any action is required.

Control Data

In-control Report Results

12s No

In-Control Report Results

Yes

no

no

no

13s

22s yes

no R4s

yes

no 41s

yes

10x yes

yes

Out-of-control, Reject analytical run

Why use a multirule QC procedure? The advantages of multirule QC procedures are that false rejection can be kept low while at the same time maintaining high error detection. This is done by selecting individual rules that have very low levels of false rejection, then building up the error detection by using these rules together. It is like running two liver function tests and diagnosing a problem if either one of them is positive. A multirule QC procedure uses two or more statistical test, (control rules) to evaluate the QC data, and then rejects a run if any one of these statistical tests is positive.

681257b51af72a5dbff337326c8378cb.doc

Ver 1.0

5/2/2021

SMILE Johns Hopkins University Baltimore, MD USA

Other common multirules used for analyzing 3 different controls 2of32s For this rule reject a control if 2 out of 3 control measurements exceed the same mean +2 or -2 control limits. 31s For this rule reject when 3 consecutive control measurements exceed the same mean +1 or -1 control limits. 6x For this rule reject when 6 consecutive control measurements of one control fall on one side of the mean.

Reference Westgard JO, Barry PL, Quam EF, Shrmeyer SS, Plaut D, Statland BE. Chapter 6 in Basic QC Practices, Training in Statistical Quality Control for Healthcare Laboratories, 2 nd Edition, Westgard QC, Inc, Madison, WI, 2002, pp77-88.

681257b51af72a5dbff337326c8378cb.doc

Ver 1.0

5/2/2021...