Which factor would most likely cause a shift in quality-control data when a new reagent lot is introduced?

• A. Change in laboratory personnel
• B. Recalibration
• C. A new reagent lot
• D. Using the same reagents

Answer: (C)

When quality-control data shifts, the most common cause is a change in the materials used, especially reagents. A new reagent lot can differ from the previous lot in potency, concentration, purity, or stabilizers, introducing a systematic bias to assay readings. That lot-to-lot variability means the same test can yield different control values with the new lot, moving QC data away from the established baseline. To handle this, laboratories validate the new reagent lot against the current one and reestablish QC expectations before relying on results.

Using the same reagents wouldn’t cause a shift because there’s no change in the material being measured. Changes in personnel can introduce variability, but they’re not tied to the introduction of a new batch of reagents. Recalibration addresses instrument drift, not inherent differences between reagent lots.