Figure 2 displays the scatterplots of the first and second fasting glucose, 2-hour glucose, and HbA1c measurements on separate plots with gridlines at clinically relevant cutoff points. The Pearson correlations for the scatterplots are indicated in the lower right-hand corners (note that the correlations for fasting glucose and HbA1c levels in this figure are slightly different than those presented in the correlation matrix because the matrix is made up of only those persons with complete OGTT results). The diagonals formed by the grid show the number of persons who tested positive on both tests using cutoff points of 100, 126, and 200 mg/dL for the fasting glucose level and 100, 140, and 200 mg/dL for the 2-hour glucose level. Because the HbA1c test is not currently recommended for use as a diagnostic test for diabetes, we compared cutoff points of 6.1%, 6.5%, and 7.0%, which were shown to be clinically relevant in previous studies.8,9 The proportion of persons with a fasting glucose level of 100 mg/dL or higher on the first test who also had a second fasting glucose level of 100 mg/dL or higher was 78.0% (95% CI, 71.8% to 83.4%). The comparable proportions for a fasting glucose level of 126 mg/dL or higher and 200 mg/dL were 70.4% (95% CI, 49.8% to 86.2%) and 100.0% (95% CI, 63.1% to 100.0%), respectively. However, in this general population, the number of persons with 2 fasting glucose measurements of 200 mg/dL or higher was small (n = 8). By contrast, the proportion of persons with a 2-hour glucose level of 100 mg/dL or higher on the first test who also had a second 2-hour glucose level of 100 mg/dL or higher was 82.8% (95% CI, 77.4% to 87.4%). The corresponding proportions for 2-hour glucose cutoff points of 140 and 200 mg/dL were 72.0% (95% CI, 62.1% to 80.5%) and 72.0% (95% CI, 52.8% to 87.3%). Using cutoff points of 6.1%, 6.5%, and 7.0% for HbA1c, the proportions were 89.0% (95% CI, 80.2% to 94.9%), 83.3% (95% CI, 67.2% to 93.6%), and 100.0% (95% CI, 76.8% to 100.0%), respectively.