IFCC Working Group Recommendations for Assessing Commutability Part 3: Using the Calibration Effectiveness of a...

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Measurement Science

Background:

• Reference materials (RMs) are crucial for accurate laboratory testing.
• Ensuring commutability of RMs across different measurement procedures (MPs) is essential for reliable clinical sample (CS) results.
• Systematic errors in calibration models can arise from calibration fit, calibrator trueness, and commutability.

Purpose of the Study:

• To describe and illustrate a process for assessing the commutability of a reference material (RM) intended for use as a calibrator.
• To evaluate the RM's ability to yield equivalent clinical sample (CS) results across multiple measurement procedures (MPs).
• To confirm the RM's fitness for purpose in a calibration traceability scheme.

Main Methods:

• A process was developed to assess RM commutability by evaluating its performance in a calibration traceability scheme.
• Systematic errors (calibration fit, calibrator level trueness, commutability) were elucidated.
• An example using 40 CS results from 7 MPs demonstrated bias and variability estimation, followed by RM-based recalibration.

Main Results:

• Recalibration with the candidate RM reduced systematic error among MPs, confirming commutability when CS results achieved acceptable equivalence.
• The RM was deemed noncommutable for MPs where post-recalibration CS results did not agree with other MPs.
• Lack of agreement necessitated investigation into other causes, such as poor calibration fit, before concluding non-commutability.

Conclusions:

• The described process effectively assesses RM commutability for calibrator use.
• Commutability is demonstrated when an RM enables equivalent CS results across MPs after recalibration.
• The RM is considered fit for purpose for specific MPs where commutability is confirmed.