Analytical goal setting prior to selection of a method for glycated haemoglobin

Abstract

Without a consensus on either a reference method or a single glycated haemoglobin standard, the individual laboratory has to establish and secure its own assay method.

Prior to selection of a method for glycated haemoglobin we used an assessment model and defined our clinical goals. Based on clinical goals it was possible to set up goals of analytical quality and evaluate available literature concerning the performance characteristics of different assay methods. We wanted a method that measured HbA_]c, without measuring the labile intermediate pre-HbA1_c, and that provided separate detection of haemoglobin variants. Low imprecision was required to secure the measured, non-diabetic reference interval, and to minimize random analytical error. We found the isoelectric focusing method the only one able to meet our goals, and a method evaluation was carried out.

Clinical goals of analytical quality should always be defined before method selection and implementation. Using this model, we were able to establish a precise isoelectric focusing method that fulfilled our clinical goals by measuring HbA1_c with a total coefficient of variation of 2.1% and a non-diabetic reference interval from 5.2% to 6.8% HbA1_c.

Key Words:

• assessment model
• glycated haemoglobin
• imprecision
• inaccuracy
• specificity