[ role of HbA1c in the diagnosis of gestational diabetes mellitus]

ABSTRACT

Gestational Diabetes Mellitus GDM is the most common metabolic disorder during the pregnancy with numerous fetal an maternal complications.It seems that the frequency of GDM is increasing so it necissitates a greater attention and more study in this field. The aim of this research is to find an alternative or at least an adjuvant method for diagnosis of GDM which is traditionally made by the time consuming and cumbersome 3 hour oral glucose tolerance test. This research is a prospectively designed study on pregnant women who were in the 24[th] to 32[nd] week of gestation. The main purpose of this study is to defining the role of HbAlc [HPLC method] in the diagnosis of GDM in comparison with the 3 hour Glucose Tolerance Test [GTT], according to carpenter- coustan criteria. 105 cases with a mean age of 29 years and an age range of 18 to 50 years were in the following groups43 persons normal,15 had impaired glucose tolerance [IGT] and 47 were in GDM group, range of HbAlc [mean +2SD] in these three groups were%3.66%5.8,%2.81-%7.45 and%2.79-%8.91 respectively. There was a significant difference [p-value<0.05] between the means of HbAlc in normal, IGT, and GDM groups but due to the wide range of variations in persons with GDM, it wasn't possible to determine a suitable lower cutoff and only the upper cutoff of%5.85 for discriminating patients with GDM from other groups especially normal persons was achieved. This cutoff was able to diagnose%38 of GDM without any normal one [no false positive result]. The most correlation exists between HbAlc with GTT3hour [r = 0.55] and fasting blood glucose [r = 0.504]. Using the upper cutoff of%5.85 for HbAlc is able to discriminate persons with GDM who have higher than this value from normal ones, but due to the wide range of variations in lower values in person with GDM and overlapping of it with the normal values,there is not a suitable lower cutoff [with high specificity and sensitivity]