Relation of fasting and postprandial and plasma glucose with hemoglobinA 1 c in diabetics

Context: Control of plasma glucose could prevent the progression of most of the complications of diabetes and hemoglobinA1c (HbA1c) is the most important criterion controlling these long-term complications. Aims: This study was performed to assess the effect of fasting plasma glucose (FPG) and twohour postprandial plasma glucose (2hpp) levels on HbA1c. Materials and Methods: In this descriptive, cross-sectional study; 300 patients were enrolled, assessed, and followed up at the clinic of the Diabetic Center of the University of Medical Science, Hamadan, Iran. All studied patients were diagnosed type 1 or 2 diabetes mellitus. Sampling was performed; we assessed FPG and 2hpp plasma glucose at baseline and at every two weeks to one month-as needed. HbA1c was assessed at the end of study. Results were analyzed by Pierson Covariance and Multiple Regression methods. Results: The mean plasma glucose in three groups of HbA1c (good to fair) were 148.5 56.80 mg/dl at fasting, and 199.70 53.01 mg/dl at two hours after breakfast (2hpp) and mean concentration of HbA1c were 8.41 1.1 %. The plasma glucose level and HbA1c were 0.312 for fasting and, 0.416 for 2hpp at covariant value. Conclusion: The postprandial (after breakfast) plasma glucose has closer association to glycosylated hemoglobin than fasting plasma glucose, therefore evaluating postprandial plasma glucose should be our focus.


Introduction
Diabetes, the most common metabolic disease, is associated with major micro and macrovascular complications. [1][4][5] Because the fl uctuations of plasma glucose level do not lend to easy analysis, we can use the hemoglobinA1c (HbA1c), which refl ects the mean plasma glucose, in the last eight to 12 weeks. [6][9] Since fl uctuations of fasting plasma glucose and postprandial could aff ect HbA1c, this study was performed to assess the relationship of fasting plasma glucose and two-hour postprandial on HbA1c.

Materials and Methods
The study was performed as a descriptive, cross-sectional, on 300 diabetic patients, type 1 or 2, at the Clinic of Diabetic Center, University of Medical Science, Hamadan, Iran.
Blood sampling was done every two to four weeks by the glucose oxidase method, at fasting and two-hour aft er breakfast (postprandial); three samples were taken on each patient in the three-month period.Mean plasma glucose was compared at fasting and postprandial separately with HbA1c level, which had been assessed at end of the study with HbA1c analyzer calibrated to give DCCT equivalent results by the chromatographicion exchange method (biosystem kit, spain).

Results
A total of 300 patients (173 female and 127 male) were included, with the minimum age of 12 years and maximum of 67 years (there was no statistical diff erence in glycemic status between 3 groups of males and females).Two hundred and thirty seven patients were diagnosed as diabetes mellitus type 2, and 63 had type 1 diabetes.Out of 237 type 2 diabetic patients, 53 patients were on insulin therapy and the others (184 patients) were on treatment with oral medications [Table 1].
The mean fasting plasma glucose and two hours aft er breakfast plasma glucose level in all three groups-of total patients were 148.0 Ϯ 56.8 mg/dl and 199.7 Ϯ 53 mg/ dlfor type1 DM; 148.9 Ϯ 51 mg/ dl and 198.56 Ϯ 52 mg/ dl and for type-2 DM were 150.6 Ϯ 48 mg/ dl and 200.3 Ϯ 47 mg/ dl-respectively and the diff erence was statistically signifi cant (P Ͻ 0.0001).
There was a linear relation, using multiple regression analyzers between HbA1c and plasma glucose level in type 1, type 2 and all patients (P Ͻ 0.0001).

Discussion
Our results indicate that postprandial glucose level increased in all three groups, and has a strong relationship with the rising of HbA1c level.Increasing of HbA1c has shown more dependency with postprandial plasma glucose as compared to with fasting plasma glucose level.
6] A number of studies have demonstrated that HbA1c has more relation to postprandial plasma glucose level, than fasting plasma glucose, [17,18] but on the contrary, Bonora et al., have observed that HbA1c has close relation to fasting plasma glucose and not to the postprandial plasma glucose level. [19,20][23] The UKPDS study, with its focus on fasting plasma glucose, did not show signifi cant reduction in macrovascular complications [15] but in those studies where focus was on postprandial plasma glucose monitoring, bett er reduction of macrovascular complications.was[9] The results of this study have shown that more than two-thirds of the patients are in poor glycemic control and exposed to the possibility of late-onset diabetic complications.