Are there new (Erna Lenters-)"Westra Rules" for HbA1c?

Posted by Sten Westgard, MS

Erna Lenters-Westra and Emma English have a new paper in CCLM:

Evaluating new HbA1c methods for adoption by the IFCC and NGSP reference networks using international quality targets, Erna Lenters-Westra, Emma English, Clin Chem Lab Med. 2017 Aug 28;55(9):1426-1434. doi: 10.1515/cclm-2017-0109

They continue the standard set by the IFCC Task Force on Implementation of HbA1c standardization (TF-HbA1c) that advocates the Sigma-metric approach as the model for setting and evaluating quality targets for HbA1c. "The TF-HbA1c has set default risk levels of 2 [Sigma] for routine laboratories and 4 [Sigma] for laboratories performing clinical trials."

Further, the paper established its own allowable total error for evaluation:

"The total allowable error (TAE) for HBA1c has been set by the TF-HbA1c as a default of 5 mmol/mol (0.45% DCCT) at an HbA1c level of 50 mmol/mol (6.7% DCCT), which corresponds with a relative TAE of 10%... in SI units [6.9% DCCT units...]"

In conversation with Dr. Lenters-Westra, she has outlined a fleshed-out set of analytical performance acceptability specifications:

• CV in CLSI EP-5 should be at 48 mmol/mol and 75 mmol/mol < or equal to 3% in SI units or < or equal to 2% in DCCT units
• Bias in CLSI EP-9 at 48 mmol/mol and 75 mmol/mol compared with the mean of at least 3 certified secondary reference measurement procedures should < or equal to 2 mmol/mol or < or equal to 0.2% DCCT units.

Perhaps we should refer to these as (Lenters-)"Westra Rules" for HbA1c?

Want to hear more about this? We encourage you to attend the Quality in the Spotlight Conference in 2018, where Dr. Lenters-Westra will lecture extensively on her work (as well as receive the Westgard Award).