Pathogenetic mechanisms and cardiovascular risk: differences between HbA(1c) and oral glucose tolerance test for the diagnosis of glucose tolerance.
Level 4 - case-series / case-control
Cross-sectional diagnostic comparison study
PubMed 22912427 · doi:10.2337/dc11-2504
What was done
The authors compared 75-g oral glucose tolerance test (OGTT) and HbA1c diagnostic classifications in 844 subjects (44% men; mean age 49.5 ± 11 years; mean BMI 29 ± 5 kg/m²). Beta-cell function was evaluated via plasma C-peptide deconvolution, insulin resistance was assessed using HOMA-IR, and cardiovascular risk factors (plasma lipids, weight, waist circumference, blood pressure) were measured across diagnostic categories.
What was found
OGTT classified 42% of subjects as having prediabetes and 15% as having type 2 diabetes mellitus (T2DM), compared with 38% and 11% by HbA1c, respectively. Concordance between tests was 54% for prediabetes and 44% for T2DM. Adjusted for age, sex, and BMI, prediabetes and T2DM diagnosed by OGTT were associated with a greater chance of insulin resistance and impaired insulin secretion. Individuals meeting both diagnostic criteria exhibited greater metabolic impairment and worse cardiovascular risk profiles than those classified as normal by both tests.
Why it matters
HbA1c identifies a smaller proportion of dysglycemic individuals than OGTT and misses a subset of patients with impaired insulin sensitivity and secretion. However, individuals positive on both tests carry the greatest metabolic and cardiovascular risk burden.
Limits
The study is cross-sectional, precluding longitudinal evaluation of clinical cardiovascular outcomes. The abstract does not report exact odds ratios, confidence intervals, or specific numerical values for lipid and blood pressure measurements.
Cited by
- supports American Diabetes Association publications acknowledge that hemoglobin A1C and fasting glucose miss over half of prediabetes and diabetes cases.