Comparing analytic performance criteria: evaluation of HbA1c certification criteria as an example

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Analytical Chemistry

Background:

• Direct comparison of analytical performance criteria using different statistical methods poses challenges.
• Standardization programs like NGSP and CAP use distinct statistical approaches for HbA1c analysis criteria.
• Inconsistency between these schemes can complicate performance evaluations.

Purpose of the Study:

• To develop a mathematical approach for comparing analytical performance criteria for HbA1c.
• To enhance consistency between the NGSP and CAP standardization schemes.
• To mathematically compare CAP and proposed NGSP criteria for HbA1c analysis.

Main Methods:

• Calculated imprecision (CV) and bias combinations for passing criteria at various probabilities (0.95, 0.99, 0.999).
• Constructed contour plots to visually compare criteria.
• Mathematically determined CV/bias requirements for CAP (3/3 results within ±7%) and NGSP (33/40 to 40/40 results within ±7%) criteria; used simulations for existing NGSP criterion (95% CI of differences within ±0.75% HbA1c).

Main Results:

• Requiring 37 of 40 results to be within ±7% of the NGSP target closely matched the CAP criterion at zero bias.
• This specific NGSP criterion demonstrated a 95% chance of passing when aligned with the CAP standard.

Conclusions:

• The NGSP Steering Committee recommended a certification criterion of 37 of 40 results within ±7% (later reduced to ±6%).
• The developed mathematical evaluation approach can be applied to compare other performance criteria.
• This method aids in harmonizing performance standards across different laboratory accreditation bodies.