[Reproducibility of the glucose tolerance test in patients with impaired fasting glucose].

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.