Westguard Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Westguard and links to relevant pages within the course.
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| 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 greater than ± 2 standard deviations from the mean on the same day of testing or if the same control is greater than + 2 standard deviations on two consecutive measurements 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 states that the run should be rejected if four consecutive control measurements have exceeded the same mean plus 1 standard deviation or the same mean minus 1 standard deviation. | 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 |