Relationship between analytical imprecision and coefficient of determination (R²) of the calibration curve

Quantitative measurement procedures rely on calibration curves, which describe the relationship between known concentrations from the calibrator material and signal intensity from the instrument, for the estimation of measurand concentration. In cases where a calibration curve is defined by a linear regression fit, acceptability criteria to determine if a calibration curve is suitable for patient reporting include a coefficient of determination (R²) of ≥ 0.99 or ≥ 0.995. However, it is unclear if such a universal criterion for R² is suitable for different analytical imprecision and measurement range profiles. Here, we examined the relationship between analytical imprecision and coefficient of determination when applied to a linear regression calibration curve.