Evaluation of Glycaemic Indices in the Assessment of Diabetic Patients
The aim of the study was to compare between the use of biochemical parameters: fasting plasma glucose (FPG), two hour postprandial plasma glucose (2hr.PPG), glycated hemoglobin (HbA1c) and fructosamine in evaluating the glycaemic control in diabetic patients and to assess the contribution effect of FPG and 2hr.PPG levels on the HbA1c, as well as to diagnose the prediabetic cases by 75gm Oral Glucose Tolerance Test (OGTT).
A case-control study design was adopted at Al-Wafaa diabetic clinic in Mosul. A total of 180 subjects were recruited during the period from November 2010 to April 2011. Thirty apparently healthy normoglycaemic volunteers as control group, one hundred and twenty diabetic patients were classified into four groups according to the types of treatment and thirty borderline cases of diabetic mellitus were subjected to OGTT. Fasting and 2hr. postprandial blood samples were separated and used to measure the biochemical parameters using commercially available kits. The Body mass index (BMI) was calculated.
The biochemical parameters measured were FPG, 2hr PPG, glycated hemoglobin (HbA1c), serum fructosamine and albumin.
The study revealed that in the four groups of various treatment, 2hr PPG showed a highly significant correlation with HbA1c, more than that of FPG (P<0.001), while FPG showed a significant correlation with fructosamine more than that of 2hr.PPG. More than 60% of patients had poor glycaemic control with HbA1c level ≥ 8%, by using Receiver Operating Characteristics Curve (ROCC). The area under the curve (AUC) of FPG was not different from that of HbA1c while that of PPG smaller.
The patients on glibenclamide therapy showed a significant difference from the diet group on the 2hr.PPG, also the patients on insulin with metformin showed a significant difference from the diet group in FPG, 2hr. PPG, HbA1c and fructosamine. The duration of diabetes mellitus showed a significant correlation with HbA1c level, but not significant with age and sex. The fructosamine showed a significant correlation with HbA1c (P < 0.001),but with Area Under the Curve (AUC) was less than fasting and postprandial plasma glucose. The results of patients who underwent Oral Glucose Tolerance Test showed that 60% of them have Impaired Glucose Tolerance (IGT),7% have Impaired Fasting Glucose (IFG), 7% have diabetic and 26% were normal according to the World Health Organization (WHO) criteria for the diagnosis of diabetes mellitus.
The study concluded that the PPG is correlated better than FPG to HbA1c. Thus the PPG is the main predicator for overall glycaemic control and should be measured in combination with FPG and HbA1c for proper assessment of glycaemic control, PPG has more contribution to HbA1c level for the state of control while the FPG has the main contribution effect when the glycaemic control is deteriorated at HbA1c level ≥ 8%. Therefore, therapy should be focused on both. Fructosamine should not be considered as a substitute for the determination of glycated haemoglobin, but rather as a complementary determination, leading to the improved laboratory control of the diabetic patient. The OGTT is more sensitive and specific than the FPG in the diagnosis of prediabetic patients. Therefore, FPG alone is unable to diagnose them and should be used with OGTT to confirm the diagnosis. Duration of diabetes had a clear influence on glycaemic level. Patients with recently diagnosed diabetes (duration of disease<5 years) had the best glycaemic control.