Correlation of Glycosylated Hemoglobin And Oral Glucose Tolerance Test Results In Hyperinsulinemic Pre-Impaired Glucose Tolerance State Versus Normoinsulinemic-Normal OGTT


Background: Prediabetes is an intermediate stage prior to development of diabetes mellitus. Pre-impaired glucose tolerance state represents an early stage in the pathogenesis of diabetes wherein the normal glucose is attained by compensated hyperinsulinemia. Glycosylated hemoglobin is used in diagnosis and monitoring of diabetes but has not been explored in pre-IGT state. The objective of this study is to compare the 2-hour blood glucose, 2-hour insulin level, and HbA1c between normoinsulinemic-normal OGTT and pre-IGT groups.

Methods: Conducted at University of Santo Tomas Hospital, this was a retrospective analytical study of high-risk individuals for evaluation of type 2 diabetes from 2000-2011 and underwent 75-gm OGTT with 2-hour blood sugar and insulin determinations. The 2-hour glucose, insulin level and HbA1c in normoinsulinemic-normal OGTT were compared with the pre-IGT group using t-test. Correlation between the 2-hour blood glucose and insulin level with the HbA1c was done using Pearson correlation analysis. Statistical significance was considered for p-value of <0.05.

Results: Second-hour blood glucose and insulin levels were significantly higher in the pre-IGT group as compared to the normoinsulinemic-normal OGTT group (128.60±18 and 89.29±68.82 vs. 90.68±26 and 17.40±8.15). The HbA1c of the pre-IGT group was significantly higher than the normoinsulinemic-normal OGTT group (6.09±0.55 vs. 5.15±0.25, p-value <0.001). There was weak positive correlation between the HbA1c and 2-hour blood glucose levels between the two groups but not with the insulin levels.

Conclusion: The pre-IGT groups have significantly higher 2nd hour blood sugar, insulin and HbA1c levels. This suggests that indeed the metabolic abnormality must be addressed as early as the pre-IGT stage.

Keywords: prediabetes; HbA1C; hyperinsulinemia; normoinsulinemic

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