Westgard rules are used in quality control to:

• A. Interpret control results and decide if a run is acceptable.
• B. Label specimens.
• C. Set reagent lot numbers.
• D. Train personnel.

Answer: (A)

Westgard rules are a quality control tool used to interpret control results and decide whether a laboratory run is acceptable. They consist of a set of criteria applied to control measurements to detect both random and systematic errors, helping to distinguish when results are reliable from when the run should be flagged or rejected. By looking at how control values behave over time and applying these rules, a lab can determine if the assay performance is in control or if a problem has occurred that could affect patient results. This focused purpose—evaluating control data to make an acceptance decision for the run—explains why it’s the best choice.

They are not about labeling specimens, setting reagent lot numbers, or training personnel, which are different aspects of lab workflow and quality management.