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

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 degrees C in normal saline to remove the labile fraction of GHb. SI-GHb was always lower than WB-GHb (p less than 0.0001). MGB correlates closely with WB-GHb (r = 0.58, p less than 0.001) and less closely with SI-GHb (r = 0.45, p less than 0.05). The daily fluctuations in SI-GHb were always significantly less than in WB-GHb (p less than 0.005). The labile fraction correlated closely with MAGE (r = 0.62, p less than 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 liable forms of GHb; (2) a closer correlation of short-term control with WB-then SI-GHb; and (3) highlight the possible relationship of the labile fraction of GHb to diabetic instability as assessed by MAGE.