Westgard Rule R4s

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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.

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Westgard Rule R4s

The R4s rule applies to controls within a run. If two controls exceed 4SD, that is, if one control exceeds +2SD and the other control (or another control, if more than 2 controls are tested) exceeds -2SD, the run should be rejected. This is the case on day 13, as seen on the normal and abnormal L-J QC charts on the right.