Table 2.
Baseline HbA1c cutoffs, AUC and its 95% Wald CI, and PLR overall and by sex and racial/ethnic subgroups (“other” race/ethnicity not presented)*
| Groups | N | HbA1c cutoff | AUC | PLR |
|---|---|---|---|---|
| Overall | 584 | 6.2 | 0.71 (0.66-0.75) | 2.94 |
| Female | 380 | 6.4 | 0.71 (0.66-0.76) | 7.37 |
| Male | 204 | 5.6 | 0.71 (0.63-0.78) | 1.74 |
| Non-Hispanic Black | 201 | 6.4 | 0.71 (0.64-0.79) | 4.27 |
| Hispanic | 233 | 6.2 | 0.68 (0.61-0.75) | 2.93 |
| Non-Hispanic White | 106 | 5.6 | 0.78 (0.67-0.87) | 2.30 |
| Female Non-Hispanic Black | 141 | 6.4 | 0.75 (0.67-0.83) | 5.78 |
| Female Hispanic | 140 | 6.3 | 0.66 (0.57-0.75) | 5.47 |
| Female Non-Hispanic White | 66 | 5.4 | 0.82 (0.68-0.95) | 2.60 |
| Male Non-Hispanic Black | 60 | 6.0 | 0.62 (0.44-0.81) | 1.91 |
| Male Hispanic | 93 | 5.5 | 0.70 (0.59-0.82) | 1.92 |
| Male Non-Hispanic White | 40 | 5.6 | 0.72 (0.55-0.88) | 2.00 |
Abbreviations: AUC, area under the curve; HbA1c, glycated hemoglobin A1c; PLR, positive likelihood ratio.
*Based on overall sample size of n = 584 (n = 174 without loss of glycemic control during 2004-2014 plus n = 410 with loss of glycemic control during 2004-2014; Figure 1). AUC is a measure of diagnostic accuracy ranging from 0 to 1, where 0.5 is equivalent to a coin toss; AUC values 0.6-0.7 represent poor ability to predict failure, values 0.7-0.8 represent fair ability, and 0.8-0.9 represent good ability. The TODAY cohort is predominantly female and minority, which affects the overall estimates (eg, the male baseline HbA1c cutoff identified via the Youden index 0.8% below the female one). The AUC 95% CI includes 0.50 only for the male non-Hispanic Black subgroup (n = 60) indicating that the cutoff is equivalent to simply guessing. A PLR (sensitivity/1-specificity) > 1 indicates the test result (HbA1c) is associated with presence of the disease, and the larger the PLR, the greater the likelihood of disease.