Significance of 2-hour blood glucose after standardized steamed bread meal in diabetic screening

Abstract

To explore the significance of 2-hour blood glucose after standardized steamed bread meal (SB-2 hBG) in diabetic screening. A retrospective study was conducted for diabetic screening data of annual check-up at PLA General Hospital from May 1996 to June 2002. And 100 g standardized steamed bread meal test was performed for non-diabetic subjects. Those subjects with SB-2 h BG ≥ 7.2 mmol/L underwent a 75 g oral glucose tolerance test (OGTT) within 2 weeks to determine whether the diagnosis of diabetes mellitus (DM) could be established (WHO, 1985, 1999, Diagnostic Criteria for Diabetes). By extracting the data for 7 consecutive years, we analyzed the significance and the cut-off point of SB-2 hBG in the diagnosis of DM and investigated the changes of blood glucose curves in different glucose tolerance status after different glucose loading tests. A total of 3 343 subjects with complete information were recruited. There were 3 101 males and 242 females with an age range of 40-94 years. According to the results of OGTT, 429 (12.8%) subjects were diagnosed as DM, 1 405 (42.1%) were diagnosed as impaired glucose regulation (IGR) and 1 509(45.1%) had normal glucose tolerance (NGT).With a deterioration of glucose tolerance status, the difference between SB-2 hBG and OGTT-2 hBG increased gradually in 3 group (P < 0.01), namely the NGT group 1.7 (0.8-2.8) mmol/L, IGR group -0.4 (-1.2-0.6) mmol/L, DM group -2.7(-3.8-1.1) mmol/L. The cut-off points of FBG for the diagnosis of IGR and DM were 5.3 (sensitivity of 46.2%, specificity of 68.5%) and 5.6 (sensitivity of 57.4%, specificity of 76.4%) mmol/L respectively. The cut-off points of SB-2 h BG were 8.2 mmol/L for the diagnosis of IGR (sensitivity of 63.8%, specificity of 59.9%) and 9.2 mmol/L for the diagnosis of DM (sensitivity of 66.4%, specificity of 76.4%).If the cut-off point of SB-2 h BG was set at 7.2 mmol/L, the diagnostic specificity became quite low.However, at 11.1 mmol/L, the sensitivity was 31.5% and the specificity 95.7% for the diagnosis of DM. The coincidences of cut-off points of FBG and SB-2 hBG for the diagnosis of IGR and DM were equal (P > 0.05).When the cut-off point of SB-2 h BG was set at 7.8 mmol/L, the sensitivity was 77.4% and the specificity 41.8% for the diagnosis of IGR. And it was much better than FBG at 5.6 mmol/L (P < 0.01). With a deterioration of glucose tolerance, the difference between SB-2 hBG and OGTT-2 hBG increases gradually. Compared to the diagnostic criteria of OGTT, the optimal cut-off points for the diagnosis of IGR and DM were 5.3 vs 5.6 mmol/L for FBG and 8.2 vs 9.2 mmol/L for SB-2 hBG respectively.For diabetic screening in middle-aged and elders, the cut-off points of FBG at 5.3 mmol/L and SB-2 hBG at 7.8 mmol/L are indicators for further OGTT.