A three-way comparison of glycated haemoglobin: are results from the three platforms interchangeable?

To determine whether glycated haemoglobin (HbA1c) results from three commonly used platforms can be interpreted cumulatively and used interchangeably in individuals with common haemoglobinopathies. A secondary goal was to assess the relationship between HbA1c concentrations, and haemoglobin and mean corpuscular volume in this population.

One hundred and forty-five samples, mostly with haemoglobinopathies, were tested by each of: Roche Gen.3 Cobas c513, Capillarys 2 Flex-Piercing and Bio-Rad D-100 platforms. Statistical comparisons and limits of performance based on biological variation, international recommendations, and local diagnostic cut-offs were drawn upon to determine comparability of results.

Inter-platform measurements were not significantly different for the large majority of results. The four HbA1c results that showed maximum discrepancy between triplicates had the following abnormalities: heterozygous haemoglobin S/ beta thalassemia, heterozygous haemoglobin S/ alpha thalassemia, beta thalassemia trait and alpha thalassemia trait. Six triplicates of results in the thalassemia groups (7.5% of thalassemia samples) had levels that misclassified patients' glycaemic status. There was no correlation between HbA1c concentration and mean corpuscular volume, and a weak negative correlation between HbA1c concentration and haemoglobin concentration.

HbA1c concentrations measured by Cobas c513, Capillarys 2 Flex-Piercing and the Bio-Rad D-100 were found to be comparable in the large majority of samples. While discordance was due to assay imprecision in some cases, in others no biological or analytical explanation could be found.