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

Abstract

Objective Reliable identification of individuals at risk for developing diabetes is critical to instituting preventative strategies. Studies suggest that the accuracy of using A1c as a sole diagnostic criterion for diabetes may be variable across different ethnic groups. We postulate that there will be lack of concordance between A1c and the Oral Glucose Tolerance Test (OGTT) for diagnosing prediabetes across Hispanic and Non-Hispanic White (NHW) populations. Research Design and Methods 218 asymptomatic adults at risk for Type 2 Diabetes (T2D) were assessed with A1c and OGTT for the diagnosis of prediabetes. Glucose homeostasis status was assigned as no diabetes (A1c < 5.7%), prediabetes (A1c 5.7% – 6.4%), and T2D (A1c > 6.4%). Inclusion criteria were age > 18 years and at least one of the following: a family history of diabetes, a history of gestational diabetes, Hispanic ethnicity, non-Caucasian race, or obesity. Subjects received a fasting 75-gram OGTT and A1c on the same day. Bowker’s Test of Symmetry was employed to determine agreement between the tests. Results Data from 99 Hispanic patients and 79 NHW patients were analyzed. There was no concordance between A1c and OGTT for Hispanic (p=0.002) or NHW individuals (p=0.003) with prediabetes. Conclusions A1c is discordant with OGTT among Hispanic and NHW subjects for the diagnosis of prediabetes. Sole use of A1c to designate glycemic status will result in a greater prevalence of prediabetes among Hispanic and NHW New Mexicans.

Discordance between HbA1c and glycemia

“…For undefined reasons, some populations show only moderate agreement of HbA1c with fasting and 2‐h post load plasma glucose values. Further, for diagnosis of prediabetes, HbA1c was reported to be discordant with blood glucose values in Asian Indians in India, and in Hispanics and non‐Hispanic Whites in the southern US . Further, in obese subjects, poor correlation of HbA1c and glycemia estimated by an oral glucose tolerance test was seen, similar to the stronger correlation of obesity with solitary high (vs HbA1c) in the study of Rathmann et al in the present issue of the Journal.…”

Prevalence of Prediabetes and Undiagnosed Diabetes Among Kuwaiti Adults: A Cross-Sectional Study

“…38 On the other hand, it has been shown that HbA1c is more specific but less sensitive than OGTT in diagnosing T2DM. [39][40][41] Nevertheless, there is no evidence that one test should be preferred to diagnose T2DM. 40 For instance, in the DETECT-2 study (~45,000 participants), neither the OGTT, HbA1c, nor FPG showed an advantage over the others in identifying diabetes-specific retinopathy.…”

Significance of prediabetes as a nosological entity

“…Some studies have shown that FPG alone may be inadequate for detecting prediabetes while higher detection rates were reported when OGTT and HbA1c were used 12 . But even these two criteria may be discordant, as suggested by Camacho et al in their study (n=218) demonstrating a significant difference between these two tests for the diagnosis of prediabetes among Hispanic and non-Hispanic white populations 13 .…”