HbA1c Test as a Tool in the Diagnosis of Gestational Diabetes Mellitus

Abstract

AimsGestational diabetes mellitus (GDM) is a prevalent and potentially serious condition which may put both mothers and neonates at risk. The current recommendation for diagnosis is the oral glucose tolerance test (OGTT). This study aimed to determine the usefulness of HbA1c test as a diagnostic tool for GDM as compared to the traditional criteria based on the OGTT.MethodsThis was a diagnostic test accuracy study. We performed OGTT and HbA1c test in women attending prenatal visits at a tertiary hospital. GDM was defined according to WHO1999 or ADA/WHO 2013 criteria. ROC curve was used to evaluate the diagnostic performance of HbA1c. Sensitivity, specificity and likelihood ratios for different HbA1c cut-off points were calculated.ResultsOf the 262 women in the third trimester of gestation enrolled in the study, 86 (33%) were diagnosed with GDM. Only five of these women presented HbA1c ≥48 mmol/mol (6.5%). This cut-off point presented 100% specificity but very low sensitivity (7%). Based on ROC curve, and considering OGTT as the reference criterion, HbA1c ≥40 mmol/mol (5.8%) showed adequate specificity in diagnosing GDM (94.9%) but low sensitivity (26.4%). Unlike, HbA1c values of 31 mmol/mol (5.0%) presented adequate sensitivity (89.7%) but low specificity (32.6%) to detect GDM. For women with HbA1c ≥40 mmol/mol (5.8%), the positive and negative likelihood ratios were 5.14 (95%CI 2.49–10.63) and 0.78 (0.68–0.88), respectively. The post-test probability of GDM was about 40%, representing a 4.0-fold increase in the mean pre-test probability. This cut-off point could eliminate the need for the unpleasant and laborious OGTT tests in almost one third of cases, as 38% of patients with GDM may be diagnosable by HbA1c test alone.ConclusionsOur results show that combined HbA1c and OGTT measurements may be useful in diagnosing GDM.

Mid‐trimester glycosylated hemoglobin levels (HbA1c) and its correlation with oral glucose tolerance test (World Health Organization 1999)

“…In our study using WHO 75 g OGTT criteria, the prevalence of GDM as per WHO OGTT criteria was 19.6% (51/260). In another study by Renz et al . the prevalence of GDM was reported to be 33%.…”

“…In our study using WHO 75 g OGTT criteria, the prevalence of GDM as per WHO OGTT criteria was 19.6% (51/260). In another study by Renz et al 17 the prevalence of GDM was reported to be 33%. Conversely, Soumya et al 18 and Khalafallah et al 11 reported a lower prevalence of GDM at 9% and 11.9%, respectively, using the OGTT criteria.…”

Elevated glycated hemoglobin predicts macrosomia among Asian Indian pregnant women (WINGS-9)

“…[19] Another study from Brazil which evaluated the performance of HbA1c as diagnostic tool for GDM showed that a cutoff of 5.4% (36 mmol/mol) has the optimal sensitivity and specificity, but the sensitivity of 70% is still not satisfactory. [20]…”

HbA1c: a review of non-glycaemic variables

“…A number of studies have demonstrated that pregnancy-specific HbA1c reference ranges could be developed to reduce those patients requiring OGTT 67. In a 2015 study, a threshold of 5.8% had a sensitivity of 26.4% and specificity of 94.9% with 38% of participants diagnosable based on HbA1c alone 68. Furthermore, use of HbA1c in this manner may facilitate screening a wider population, thereby detecting patients with GDM who fail to complete or are not detected by an OGTT 69.…”