Glycated hemoglobin versus oral glucose tolerance test in the identification of subjects with prediabetes in Qatari population

Background: Glycated hemoglobin (HbA1c) levels are dependent not only on the average blood glucose levels over the preceding 2 - 3 months but also on the turnover of erythrocytes. Hyperthyroidism is known to be associated with an increase in erythrocyte turnover that may falsely lower the HbA1c in relation to the level of glycemia. Objectives: To assess the impact of medical correction of hyperthyroidism on HbA1c, independent of changes in the fasting plasma glucose and 2-hour post-oral glucose tolerance test plasma glucose. Methods: Adult patients with overt hyperthyroidism (n = 36) were tested for their hemoglobin, reticulocyte percentage, HbA1c and fasting and post-oral glucose tolerance test (OGTT) 2-hour plasma glucose, both at baseline and following at least three months of near normalization of serum thyroxin on Carbimazole treatment. Results: Correction of hyperthyroidism in 36 patients was associated with an increase in the hemoglobin (P = 0.004) and a rise in HbA1c (P = 0.025), even though no significant change was observed in both the fasting (P = 0.28) and post OGTT two-hour plasma glucose (P = 0.54). Also, the proportion of patients with HbA1c ≥ 5.7% rose from 3/36 to 10/36; P = 0.016, while the proportion of patients with either abnormal fasting or abnormal post OGTT 2-hour plasma glucose or both did not show any significant change (P = 0.5). The sensitivity of HbA1c to diagnose prediabetes increased from 20% to 50% post- treatment. Conclusions: Glycated hemoglobin is falsely low in relation to glycemia in patients with untreated hyperthyroidism.

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Utility and Limitations of Glycated Hemoglobin (HbA1c) in Patients with Liver Cirrhosis as Compared with Oral Glucose Tolerance Test for Diagnosis of Diabetes

Diabetes Therapy ◽

10.1007/s13300-017-0362-4 ◽

2018 ◽

Vol 9 (1) ◽

pp. 243-251 ◽

Cited By ~ 4

Author(s):

Tejasav Sehrawat ◽

Anuraag Jindal ◽

Paaras Kohli ◽

Amit Thour ◽

Jasbinder Kaur ◽

...

Keyword(s):

Liver Cirrhosis ◽

Glucose Tolerance ◽

Oral Glucose Tolerance Test ◽

Glucose Tolerance Test ◽

Glycated Hemoglobin ◽

Tolerance Test ◽

Oral Glucose ◽

Oral Glucose Tolerance

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Response to Comment on: Boronat et al. Differences in Cardiovascular Risk Profile of Diabetic Subjects Discordantly Classified by Diagnostic Criteria Based on Glycated Hemoglobin and Oral Glucose Tolerance Test. Diabetes Care 2010;33:2671-2673

Diabetes Care ◽

10.2337/dc11-0350 ◽

2011 ◽

Vol 34 (5) ◽

pp. e60-e60

Author(s):

M. Boronat ◽

F. J. Novoa

Keyword(s):

Cardiovascular Risk ◽

Glucose Tolerance ◽

Oral Glucose Tolerance Test ◽

Glucose Tolerance Test ◽

Glycated Hemoglobin ◽

Tolerance Test ◽

Risk Profile ◽

Oral Glucose ◽

Oral Glucose Tolerance ◽

Cardiovascular Risk Profile

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The Performance of Glycated Hemoglobin Versus Oral Glucose Tolerance Test in the Diagnosis of Glycemic Disorders Among Women With Polycystic Ovary Syndrome in Southern Iraq

Journal of the Endocrine Society ◽

10.1210/jendso/bvab048.891 ◽

2021 ◽

Vol 5 (Supplement_1) ◽

pp. A437-A437

Author(s):

Mahmood Thamer Altemimi ◽

Alaa Khattar Musa ◽

Abbas Ali Mansour

Keyword(s):

Risk Factor ◽

Glucose Tolerance ◽

Oral Glucose Tolerance Test ◽

Screening Tool ◽

Glucose Tolerance Test ◽

Glycated Hemoglobin ◽

Tolerance Test ◽

Oral Glucose ◽

Oral Glucose Tolerance ◽

Southern Iraq

Abstract Background: Obese women with PCOS are at high risk for developing diabetes mellitus (T2DM). A baseline oral glucose tolerance test (2hrs-OGTT) annually is an important to screen for dysglycemia in women with PCOS particularly those with at least one risk factor. Due to its advantages by fasting is not required and less day-to-day variability during periods of stress or illness, glycated hemoglobin (HbA1c) might consider a convenient screening tool. This study aimed to evaluate the performance of HbA1c versus 2hrs-OGTT in the diagnosis of glycemic disorders in women with PCOS and to evaluate the correlation between glycemic disorders, insulin resistance (IR), and anthropometric measures. Patients and methods: One hundred and thirty women of a mean age 26.3 ± 6.85 year were diagnosed with PCOS according to Rotterdam 2003 criteria in Basrah, Southern Iraq. All women were examined for weight, BMI and waist circumference then they were sent for fasting plasma glucose (FPG), 2hrs-OGTT, HbA1c, and fasting insulin to assess IR. Results: By 2hrs-OGTT, impaired glucose tolerance and T2DM were diagnosed in 16.1% and 2.4% of women with PCOS respectively and 6.7% of lean women were prediabetes. HbA1c was underestimate the diagnosis of T2DM (0.8%) and overestimate prediabetes (20%) (p=0.011) and at HbA1c= 5.55%, the specificity was (74.3%) and sensitivity (56.5%) to discriminate normal from abnormal glucose status in women with PCOS (AUC: 0.645; 95% C.I.: 0.503–0.77; p = 0.03). One hundred women (76.9%) were either overweight or obese and most of them had IR (78%). Conclusion: screening of glycemic disorders is a crucial for PCOS by using 2hrs-OGTT regardless risk factor and HbA1c seems to be unsatisfactory screening tool to predict glycemic disorders in women with PCOS.

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