Abstract
We read with interest the recent editorial which discussed the advantages offered by haemoglobin A1c (HbA1c) for the diagnosis of diabetes. 1 Routine assessment of HbA1c for establishing altered glucose homeostasis will represent a major breakthrough from both clinical and economic perspectives, influencing organization as well as resource allocation of most clinical laboratories. However, while HbA1c may have less preanalytical caveats than plasma glucose, there are several questions that, to our knowledge, are still unanswered. While we agree that diabetes is better defined in term of increased microvascular risk than glucose homeostasis, the use of HbA1c is likely to introduce a paradigm shift in the conventional diagnostic approach to diabetes, for which definitive proof of effectiveness is lacking. Moreover, blood glucose measurement is more easily, reliably and economically measured, and directly mirrors glycaemic status. 2 There are also doubts as to whether HbA1c reflects the same degree of chronic hyperglycaemia across different ages, 3 ethnicities 4 and co-morbidities (e.g. anaemia, haemoglobin variants, renal failure and alcohol abuse 5 ) and between patients with low and high glycation indices. 6 The potential adverse impact of these issues on laboratory and health-care costs is significant.
What must be clearly understood by clinicians and laboratory professionals is that HbA1c and plasma glucose are likely to be measures of two different metabolic processes and are not interchangeable. It is likely that the use of HbA1c as a surrogate of plasma glucose or the oral glucose tolerance test for diagnosing diabetes may identify a different subset of patients with impaired glucose metabolism, as well as miss others classically defined as low ‘glycators’, who might require a rather different therapeutic approach.
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