Westgard Rule 22S

How to Subscribe
MLS & MLT Comprehensive CE Package
Includes 173 CE courses, most popular
$95Add to cart
Pick Your Courses
Up to 8 CE hours
$50Add to cart
Individual course$20Add to cart
Need multiple seats for your university or lab? Get a quote
The page below is a sample from the LabCE course Quality Control. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

Learn more about Quality Control (online CE course)
Westgard Rule 22S

  • Westgard rule 22s states that if two consecutive control measurements exceed the same mean +2SD or -2 SD or, within a run, if two consecutive control values are outside the same 2 SD, 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," but would have been rejected on the next QC run if the same control was again out +2SD.