Westguard Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Westguard and links to relevant pages within the course.
Learn more about laboratory continuing education for medical technologists to earn CE credit for AMT, ASCP, NCA, and state license renewal and recertification. Or get information about laboratory safety and compliance courses that deliver cost-effective OSHA safety training and continuing education to your laboratory's employees.
| Using Westgard Rules In 1981, Dr. James Westgard and his associates developed a multi-rule procedure for interpreting control data. Since then, a number of sophisticated quality control schemes or analogues based on this multi-rule logic have evolved. To show how the Westgard Rules may be applied in quality control, three of the most common rejection limits will be illustrated in the following pages. | View Page |
| Westgard Rule 13S Westgard rule 13s states that if a control is greater than ± 3 standard deviations from the mean, it should be rejected and rerun. This is because either a random error or a very large systematic error has occurred, as less than 1% of all test values exceed ± 3SD. In the accompanying example, the control for Day 13(noted by the arrow) is greater than +3SD from the mean. Consequently rule 13s applies and the run is rejected. Troubleshooting must be performed before further testing can be done. | View Page |
| Westgard Rule 22S Westgard rule 22s states that if two or more controls are ± 2 standard deviations or greater from the mean on the same day of testing, then the run must be rejected. If this circumstance occurs, a systematic error is likely. The top chart represents the day's "normal" control, while the bottom chart shows the day's "elevated" control. The L-J plots on the 13th day for both the normal and elevated controls show greater than +2SD. Troubleshooting must be performed before testing can continue. Had only one of the controls been greater than ± 2SD, the run would have been accepted as “in control”. | View Page |
| Westgard Rule 41s (1) Westgard Rule 41s has two main parts. The first part states that a run is to be rejected if the control values were beyond ±1SD for four consecutive testing days, the control for the fourth day is rejected. In the illustration to the right, you will notice that on the 10th, 11th, and 12th of the month, the control results were greater than ±1SD from the mean. The control was again greater than 1SD on the 13th, resulting in the testing procedure being out of control for the 13th. | View Page |
| Westgard Rule 41s (2) The second part of Westgard Rule 41s says that a run must be rejected if control values have fallen on the same side of the mean for six consecutive testing days, regardless of standard deviation. Looking closely at the plots you will observe that there has been a movement of the values from one level of the control chart to another, as though the mean has changed. Both parts of this rule reveal systematic errors and troubleshooting must be done before testing can resume. | View Page |
| CUSUM and Westgard Rules Looking at the Levey-Jennings chart you will notice that the plots correspond with the Westgard rule 41s. What type of movement and error do you think this reflects? | View Page |
| Which Westgard rule is illustrated by these normal and elevated Levey-Jennings plots? | View Page |
| Does the Levey-Jennings chart to the right show acceptable quality control results? | View Page |
| Does the Levey-Jennings chart to the right show acceptable quality control results? | View Page |
| According to the Westgard Rules, the glucose run should have been rejected on day: | View Page |