Temperature dependence of the chromatographic assay of hemoglobin A 1 and application of a temperature controlled assay to clinical evaluation of diabetic control

Abstract

We investigated the temperature dependence of the cation-exchange Chromatographie properties of hemoglobin A 1 using the “Fast Hemoglobins Test System” obtained from Isolab, Inc., Akron, OH U.S.A. and a temperature control chamber constructed in our laboratory. Six patient samples, two each from the “normal” range (5–8.5%), “transitional” range (8.5–12.0%) and “uncontrolled diabetic” range (12–20%) described by Isolab (as measured at 24°C) were collected, hemolyzed and assayed according to product insert instructions. Each sample was assayed in triplicate in three separate runs at 20°C, 22°C, 24°C, 26°C and 28°C in the temperature controlled (±0.25° C) chamber. Resultant mean increases in assay results of 0.8, 1.1 and 1.6% hemoglobin A 1 per 2°C increase in temperature for the three ranges respectively, indicate that the temperature dependence of the microcolumn assay for hemoglobin A 1 is at least partially a function of the relative percentage of glycosylated hemoglobin in the sample. By controlling assay temperature we have reduced interassay variation throughout all concentration ranges by more than one-half to less than 5%. We applied this temperature controlled assay to measurement of hemoglobin A 1 levels in 33 non-diabetic subjects and to the screening of hemoglobin A 1 levels in 77 diabetic patients regularly attending the diabetic-endocrine outpatient clinic of this hospital. No non-diabetic subject had a HbA 1 level above 8.5% and of the diabetic patients, 26% fell within the “normal” range, 43% within the “transitional” range and 31% within the “uncontrolled diabetic” range.