Utility of HbA1c for diagnosis of gestational diabetes mellitus

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Abstract

Objective

To evaluate the utility of HbA1c in combination with OGTT for diagnosis of GDM.

Materials and methods

607 pregnant women with their estimated gestational age between 24 and 28 weeks were evaluated for GDM using OGTT based on ADA criteria. HbA1c was also done at the same time.

Results

The mean HbA1c value in women with GDM was significantly higher than women without GDM (5.73 ± 0.34% compared to 5.34 ± 0.35%). The area under ROC curve of HbA1c to detect GDM was 0.805 and an HbA1c cutoff value of ≥5.95% had sensitivity of 28.6% and specificity of 97.2% in diagnosing GDM while an HbA1c cutoff value of ≥5.45% had sensitivity of 85.7% and specificity of 61.1% in diagnosing GDM. For women with an HbA1c value between 5.45% and 5.95%, an OGTT should be performed to correctly identify women with GDM. Using this methodology 85.7% of the GDM cases would have been detected and only 2.8% of normal women would have been wrongly labeled as having GDM. Also, this methodology would have obviated an OGTT in 61.8% women in our study.

Conclusion

HbA1c in combination with OGTT can obviate the need of OGTT in almost two-thirds of women with GDM.

Introduction

Gestational diabetes mellitus (GDM) is defined as glucose intolerance of any degree with first recognition during pregnancy [1]. Oral glucose tolerance test (OGTT) is the gold standard test for diagnosing GDM. Different criteria use different values for OGTT for diagnosing GDM [2], [3], [4]. OGTT, though gold standard, is a cumbersome procedure for participant as well as health care providers. It requires the participant to be in fasting state, requires at least 2 h for sample collections and minimum two blood samples are taken. The time required and samples collected can be higher depending upon the criteria followed [2], [3], [4]. World health organization (WHO) in 2011 as well as American diabetic association (ADA) has accepted HbA1c as a diagnostic tool for diagnosing diabetes mellitus [5], [6]. However, there are no recommendations available for use of HbA1c as a diagnostic tool for GDM. We carried out this study to evaluate the utility of HbA1c in diagnosing GDM.

Section snippets

Materials and methods

This study was carried out in antenatal care clinic at Post Graduate Institute of Medical Sciences (PGIMS), Rohtak, Haryana. The study protocol was approved by the local institutional ethics committee. In an earlier study done at various centers across India the prevalence of gestational diabetes mellitus was found to be 16.55% [7]. Assuming the prevalence as 16.55% and allowable percentage type II errors of 20% at level of significance of 95%, a sample of 500 eligible subjects was calculated.

Results

A total of 607 women participated in this study their baseline characteristics are shown in Table 1. Out of these 43 (7.1%) were diagnosed as having GDM based on ADA criteria while 144 (23.72%) women were diagnosed as having GDM using recently proposed International association of diabetes and pregnancy study group (IADPSG) criteria [8]. The values of HbA1c ranged from 4.0% to 6.1%. The mean ± SD HbA1c value in women with GDM was 5.73 ± 0.34% while it was 5.34 ± 0.35% in women without GDM. The

Discussion

This study has shown that though the mean HbA1c values of GDM women was significantly higher than normal women, there was considerable overlap in the HbA1c values of the two groups. The mean HbA1c level in GDM women was 5.73 ± 0.34% while it was 5.34 ± 0.35% in women without GDM. Although similar HbA1c levels (5.36 ± 0.36% normal glucose tolerance and 5.96 ± 0.63% in GDM women) were observed in an earlier study by Balaji et al., they tested women in their first trimester in contrast to recommendation

Conflict of interest

There are no conflicts of interest.

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