Diurnal glucose-dependent fluctuations in glycosylated hemoglobin levels in insulin-dependent diabetes

Abstract

In order to evaluate the relationship between short-term glycemic control and the stable and labile fractions of GHb, we performed hourly blood glucose samplings for 24 hr on 31 occasions in 13 children with IDDM of varying duration. GHb was measured both in hemolysates of whole blood and after 48 hr incubation at 4°C in normal saline to remove the labile fraction of GHb. SI-GHb was always lower than WB-GHb ( p < 0.0001). MGB correlates closely with WB-GHb ( r = 0.58, p < 0.001) and less closely with SI-GHb ( r = 0.45, p < 0.05). The daily fluctuations in SI-GHb were always significantly less than in WB-GHb ( p < 0.005). The labile fraction correlated closely with MAGE ( r = 0.62, p < 0.0001). In one subject WB-GHb decreased by 4.4% and SI-GHb by 3.1% over a 7 wk period of good glycemic control. These results (1) confirm the presence of the stable and labile forms of GHb; (2) a closer correlation of short-term control with WB-than SI-GHb; and (3) highlight the possible relationship of the labile fraction of GHb to diabetic instability as assessed by MAGE.