Abstract

Background: HbA_1c (glycohaemoglobin) is universally used in the ongoing monitoring of all patients with diabetes. There are many % HbA_1c target control rating recommendations by national, regional and international expert bodies for diabetes patients and these are variable around the world. General patient target control ratings are currently most often recommended as either <6.5% or <7.0% HbA_1c, with <6.0% HbA_1c stated for individual patients where clinically possible. This necessitates very precise HbA_1c assays and the same patient values, irrespective of HbA_1c method or area of the world.

Methods: HbA_1c targets recommended by major expert groups and published HbA_1c assay precision (coefficient of variation, %CV) levels have been detailed. These have been compared with published biological variation levels and with calculated HbA_1c error ranges at various HbA_1c levels and %CV levels. In addition, these have been compared with the analytical precision necessary to differentiate between the upper limit of the normal range for HbA_1c and targets recommended by expert groups for diabetes control.

Results: Intralaboratory analytical CVs of <2% are necessary and are achievable on automated HPLC analysers, and are supported on grounds of both clinical need and biological variation, as well as the need to differentiate the national, regional and international target recommendations from the upper limit of the normal range (<6.0% HbA_1c level).

Conclusions: Routine methods with tight long-term imprecision with CVs of <2% are recommended. International HbA_1c targets essentially require that all HbA_1c methods be precise, and have minimal standardisation bias and minimal methodological interferences in individual patients.

Clin Chem Lab Med 2007;45:1083–97.