On the importance of a prolonged dialysis for haemoglobin AIc determination

The determination of haemoglobin A,, (Hb A,,) has been demonstrated to be a valuable index of glucose equilibrium in diabetic patients [l]. Since 1978, a rapid increase in the demand for this test has caused many laboratories to utilize commercial fast evaluation kits, which give the percentage of glycosylated Hb (Hb A Ia+b+c) in less than 3 h. Unfortunately, the methods used with these kits do not eliminate the labile form of Hb A,, (Hb pre A,,) [2] containing a molecule of glucose reversibly bound through an aldimine linkage to the NH,-terminus of the P-chain of Hb A, [3]. Recent findings by Svendsen et al [4] and others [5] have shown that this unstable precursor is eluted with the true Hb A,, in the chromatographic techniques. The labile form is able to fluctuate very quickly with rapid changes of blood glucose and thus may artificially increase the level of glycosylated Hb as measured by the kits. In this paper, we introduce further evidence that prolonged dialysis of the patient’s hemolyzates against a glucose-free buffer is necessary for completely eliminating the unstable Hb Ale, and that such a step should be added to all the chromatographic techniques in order to obtain reproducible results.