University of Texas Medical Branch Effective Date: Aug 92
Pulmonary Function Clinic Revised Date: Oct 05
Policy 04-12 Westgard Rules Review Date: May 14
Westgard Rules
________________________________________________________________________
Audience All personnel in the Pulmonary Function Clinic.
________________________________________________________________________
Purpose To explain the Westgard Rule Control Rules of quality control in detail.
________________________________________________________________________
Rule 1-2s Definition: The 1-2s Control Rule indicates one control result has
exceeded the established mean +/- 2SD range. This is a “warning rule,”
which does not indicate an “out-of-control” condition, but is intended to
initiate further testing.
Interpretation: If no other control rule is violated, then the warning is
attributed to normal random error. Patient results are acceptable.
Corrective Action: No corrective action is required. However, the
“warning” suggests a system error may be in the development. A
comprehensive check of the routine maintenance schedule and review of
the quality control ampoule handling and sampling technique is
recommended.
________________________________________________________________________
Rule 1-3s Definition: The 1-3s Control Rule indicates one control result has
exceeded the established mean +/- 3SD range. This is a “rejection rule,”
which is sensitive to random error.
Interpretation: Excessive random error exists. The analyzer is “out-of-
control.” Patient results are not acceptable and should be re-analyzed after
corrective actions have solved the problem.
Corrective Action: Rerun the quality control level that is in question,
emphasizing proper technique. If the repeated level is within +/- 2SD
range then the problem can be attributed to random error. If the repeated
level exceeds the +/- 2SD range, then further corrective action should be
conducted. The following are probable causes:
Inadequate or wrong +/- 2SD range.
Improper storage temperature correction of quality control results.
Improper technique when handling the quality control.
Change of quality control batch.
Inadequate maintenance of the instrument.
_______________________________________________________________________
Rule 2-2s Definition: The 2-2s Control Rule indicates that two consecutive control
results have exceeded the same mean +/- 2SD limit. This is a “rejection
rule,” which is sensitive to systematic errors.
______________________________________________________________________________________
Page 1 of 3
Pulmonary Function Clinic Revised Date: Oct 05
Policy 04-12 Westgard Rules Review Date: May 14
Westgard Rules
________________________________________________________________________
Audience All personnel in the Pulmonary Function Clinic.
________________________________________________________________________
Purpose To explain the Westgard Rule Control Rules of quality control in detail.
________________________________________________________________________
Rule 1-2s Definition: The 1-2s Control Rule indicates one control result has
exceeded the established mean +/- 2SD range. This is a “warning rule,”
which does not indicate an “out-of-control” condition, but is intended to
initiate further testing.
Interpretation: If no other control rule is violated, then the warning is
attributed to normal random error. Patient results are acceptable.
Corrective Action: No corrective action is required. However, the
“warning” suggests a system error may be in the development. A
comprehensive check of the routine maintenance schedule and review of
the quality control ampoule handling and sampling technique is
recommended.
________________________________________________________________________
Rule 1-3s Definition: The 1-3s Control Rule indicates one control result has
exceeded the established mean +/- 3SD range. This is a “rejection rule,”
which is sensitive to random error.
Interpretation: Excessive random error exists. The analyzer is “out-of-
control.” Patient results are not acceptable and should be re-analyzed after
corrective actions have solved the problem.
Corrective Action: Rerun the quality control level that is in question,
emphasizing proper technique. If the repeated level is within +/- 2SD
range then the problem can be attributed to random error. If the repeated
level exceeds the +/- 2SD range, then further corrective action should be
conducted. The following are probable causes:
Inadequate or wrong +/- 2SD range.
Improper storage temperature correction of quality control results.
Improper technique when handling the quality control.
Change of quality control batch.
Inadequate maintenance of the instrument.
_______________________________________________________________________
Rule 2-2s Definition: The 2-2s Control Rule indicates that two consecutive control
results have exceeded the same mean +/- 2SD limit. This is a “rejection
rule,” which is sensitive to systematic errors.
______________________________________________________________________________________
Page 1 of 3
