Does HbA_1C predict isolated impaired fasting glycaemia in the oral glucose tolerance test in subjects with impaired fasting glycaemia?

Abstract

Background: To assess the usefulness of erythrocyte glycated haemoglobin (HbA 1C ) as a screening tool to identify those subjects with impaired fasting glycaemia (IFG) who do not have impaired glucose tolerance (IGT) or diabetes mellitus (DM) on a 75 g oral glucose tolerance test (OGTT). Design and methods: All subjects undergoing an OGTT had HbA 1C measured at baseline. Receiver operator characteristics analysis was used to identify optimal HbA 1C cut-off values for diagnosing and excluding IGT and DM. Results: We studied 140 subjects (69 women) with IFG (fasting capillary plasma glucose between 6.1 -6.9 mmol/L). Using World Health Organisation criteria, 27 had isolated IFG, 56 had IGT and 57 had DM. HbA 1C was higher (P , 0.001) in patients with DM (6.8 + 0.93%) when compared with those with IGT (6.3 + 0.68%) and isolated IFG (6.2 + 0.30%), but HbA 1C was similar in those with IGT and isolated IFG. There was no HbA 1C cut-off value differentiating isolated IFG from IGT or DM. None of the subjects with isolated IFG had HbA 1C concentration of .6.8%, but 76% and 54% subjects with IGT and DM, respectively, had HbA 1C of 6.8%. Conclusions: HbA 1C measurement is of limited value in differentiating isolated IFG, IGT and DM in subjects with IFG. It cannot be used to identify which subjects with IFG do not require an OGTT.

Impact of early psychosocial factors (childhood socioeconomic factors and adversities) on future risk of type 2 diabetes, metabolic disturbances and obesity: a systematic review

“…Thus, evidence from HOMA-IR-based data were considered as high (O = 1). Although HbA1c has been suggested as diagnostic tool for type 2 diabetes (ADA 2010), especially in early diabetes and in prediabetes, HbA1c values lead to misinterpretation which may be also due to a genetic component in the metabolisation of glycated haemoglobin [35-39]. Thus, we rated the quality of HbA1c values as low (O = 0).…”

Diagnostic performance of HbA1c for diabetes in Arab vs. European populations: a systematic review and meta‐analysis

“…The prevalence of diabetes in Arab populations has reached epidemic levels [11], however, few data are available regarding the performance of HbA 1c in diagnosing diabetes in this population, specifically the accuracy of the currently recommended 48 mmol/mol (6.5%) cut-point. The HbA 1c test has demonstrated low sensitivity and high specificity for diagnosing diabetes in diverse populations [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], including the Arab American population [29]. It would be expected that the interindividual variation and thus the optimal cut-point seen in HbA 1c levels among races and ethnicities would also apply to Arab populations.…”

HbA1c and diagnosis of diabetes. The test has finally come of age

“…Reliance solely on HbA1c removes the need for the OGTT, although this is only required in a small proportion of cases outside pregnancy and, crucially, it must be stressed that HbA1c is not recommended as a second step after an initial fasting plasma glucose concentration in the range 6.1-6.9 mmol/L. HbA1c is a poor predictor of the two-hour OGTT glucose concentration in patients with impaired fasting glycaemia (IFG) 15 and thus cannot overcome the need for an OGTT in this group. 16 What is the future for impaired glucose tolerance (IGT) and IFG?…”