Why are internal QC materials selected with known concentrations near medical decision levels?

• A. Because they are cheaper.
• B. Because they are easier to obtain.
• C. Because they are more stable.
• D. Because deviations at concentrations near medical decision levels are more likely to affect clinical decisions.

Answer: (D)

Focusing QC materials in the range around clinical decision levels ensures we catch errors that would actually change patient management. Small biases or imprecision near the cutoff can push a result from one category to another, leading to a different treatment or diagnostic conclusion. By using known concentrations close to these thresholds, the assay’s accuracy and precision are continuously checked where it matters most, so any drift or bias that could affect decisions is detected promptly. Other factors like cost, availability, or general stability are less directly tied to the goal of keeping decision outcomes trustworthy.