Background and objectives: Impaired fasting glucose (IFG) is defined by a fasting glucose between 5.6 and 6.9 mmol/l in subjects with no known diabetes. The present study objectives were: a) to analyze the glucose tolerance test (GTT) reproducibility and b) to assess this test's diagnostic classification agreement.
Patients and method: Cross-sectional study in adult patients diagnosed with IFG. Study subjects underwent a 75 g GTT in two occasions.
Results: Fifty-nine patients were studied. The interval between GTT tests was 37 +/- 26 days. Fasting and post-GTT plasma glucose intra-individual variation coefficients were 6.9 and 31.0%, respectively. Diagnostic agreement between the two tests (normal tolerance vs. abnormal tolerance) was measured using the kappa index: 0.62 (95% CI 0.42-0.82). Agreement ranged from 80% (95% CI, 70-90%) to 83% (95% CI, 73-93%) depending on whether the first GGT results were abnormal or normal, respectively.
Conclusions: GTT reproducibility is moderate in patients diagnosed with IFG. Considering this fact, perhaps this test should be repeated before therapeutic decisions are made.