Glycated hemoglobin for the diagnosis of diabetes and prediabetes: Diagnostic impact on obese and lean subjects, and phenotypic characterization

Abstract

Aims/IntroductionMeasurement of glycated hemoglobin (HbA1c) has been recommended for the diagnosis of diabetes and prediabetes. However, epidemiological studies have shown significant discordance between HbA1c and glucose-based tests. Of the factors that could influence agreement between HbA1c and the oral glucose tolerance test (OGTT), bodyweight has not been fully evaluated. The aims of the present study were to evaluate the impact of HbA1c criteria to diagnose diabetes and prediabetes compared with OGTT, and to examine HbA1c in relation to body mass index.Materials and MethodsTwo cohorts were studied, one from an obesity clinic (n = 592) and one from subjects undergoing screening for diabetes (n = 462). All underwent OGTT and HbA1c measurement.ResultsIn the obese cohort, HbA1c ≥6.5% (≥48 mmol/mol) showed a sensitivity of 69.3% for diabetes, whereas HbA1c 5.7–6.4% (39–46 mmol/mol) did not identify prediabetes well (sensitivity 39.1%). In the diabetes screening cohort, HbA1c had low sensitivities for both diabetes (39.2%) and prediabetes (53.3%). When participants were stratified according to body mass index class I–III, HbA1c agreement with the OGTT for diabetes was much higher (80%, P < 0.005) in class I obesity compared with class II–III obesity; whereas for prediabetes, HbA1c had a low sensitivity in all obesity classes.ConclusionsThe agreement between HbA1c, fasting plasma glucose and 2-h glucose post-OGTT for the diagnosis of prediabetes was poor in our Italian population; whereas HbA1c ≥6.5% showed a relatively good agreement with OGTT for the diagnosis of diabetes. For the first time, we have shown that obesity class influences the diagnostic performance of HbA1c.

Performance of A1C Versus Ogtt for the Diagnosis of Prediabetes in a Community-Based Screening

“…In contradistinction to other studies, there was no correlation between BMI and A1C in the current study (r=0.29, p=0.69). 30, 33 …”

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.…”

Cutoff Point of HbA1c for Diagnosis of Diabetes Mellitus in Chinese Individuals

“…HbA1c tests are convenient and can be performed at any time regardless of the time of the previous meal [3]. In Europe and the United States, an HbA1c ≥ 6.5% is used to diagnose diabetes [2, 4], but this cutoff is still controversial in China.…”