Download Full Text (730 KB)

Document Type



The purpose of this review was to evaluate the diagnostic utility of hemoglobin A1c (HbA1c) compared to oral glucose tolerance testing (OGTT) for diagnosis of type 2 diabetes. Databases ClinicalKey, PubMed, Dynamed, and CINAHL withdrew a total of 17 peer-reviewed cross-sectional and retrospective studies, secondary and pooled data analyses, and meta-analyses. Inclusion criteria included human studies, studies < 10 years old, individuals > 15 years of age, fasting plasma glucose in conjunction with OGTT, and subjects without known diabetes. Exclusion criteria included alternative forms of diabetes, screening and diagnosis of prediabetes, comparisons in relation to specific medical conditions such as heart disease, pregnancy, and gestational diabetes, prior diabetes diagnosis, and children <15 years old. Discrepancies with sole utilization of HbA1c when used to screen and diagnose type 2 diabetes mellitus were found when compared to OGTT standards. Current literature proposes race, gender, age, and obesity may be related to inaccurately low HbA1c compared to OGTT standards in patients who have not been diagnosed with diabetes. Of those, race and metabolic profiles appear to have the greatest impact in reduction of HbA1c’s sensitivity. An alternative to sole utilization of HbA1c may be increasing utilization of OGTT, especially in those with risk of erroneously low HbA1c and high risk for type 2 diabetes. Longitudinal data is needed to strengthen findings noted in this literature review


Physician Assistant Studies

Date of Work


Publication Date



Type 2 diabetes, glucose tolerance test, 2hPG, A1c.


Medicine and Health Sciences

Comparison of Oral Glucose Tolerance and Hemoglobin A1c as an Initial Indicator of Type 2 Diabetes