HbA₁ determination by agar gel electrophoresis after elimination of labile HbA₁: a comparison with ion-exchange chromatography

Abstract

A rapid and simple method, Agar gel electrophoresis (Glytrac™, Corning Medical), for HbA₁ analysis was evaluated and compared with an ion-exchange chromatography method capable of estimating HbA_{1 (a+b)} and HbA_1c separately. Preincubated samples from diabetics and normals were analysed by both methods and showed good correlation (r=0.97, n=89). The following data were obtained with agar gel electrophoresis. Incubation of erythrocytes at a glucose concentration of 30 mmol/l for 6 h at 37°C gave an increase of 1.39% HbA₁. This increase was almost reversed by reincubation in low glucose medium. By preincubation of erythrocytes in saline HbA₁ decreased 0.90 ± 0.39% HbA₁ (mean±SD) in diabetics and 0.38 ± 0.26% HbA₁ in normal controls. This preincubation step is necessary to eliminate the labile HbA₁ fraction when HbA₁ is to be used as an index of long term glucose control in diabetes. The HbA₁ ranged from 5.1 to 7.4% (n=68), mean 5.8% (SD 0.5). HbA₁ in patients with juvenile diabetes ranged from 6.1 to 19.3%. Within-run precision (CV) was 2.3 and 2.5% in normal and diabetic samples, respectively. Between-run precision was 5.7%. Variation in temperature between 18.5 and 31.5°C did not affect the HbA₁ values significantly. Within-run and between-run precision for chromatography was 3.4 and 4.7% respectively. Agar gel electrophoresis is a simple and rapid method for HbA₁ determination, with acceptable precision and accuracy.

Key-words:

• diabetes mellitus
• glucose control
• fast-glycosylated HbA₁
• labile HbA₁
• HbA_1c
• glycosylated haemoglobin