Table 4.
C-Index and Integrated Discrimination Improvement Over the Baseline Cardiovascular Risk Factors Model
| Model | C-Index | IDI | |||
|---|---|---|---|---|---|
|
| |||||
| C* | ΔC (95% CI) | P Value | IDI, % (95% CI) | P Value | |
| All-cause mortality | |||||
| BRF† | 0.701 | ref | ref | ref | ref |
| BRF + distance score | 0.735 | 0.034 (0.010 to 0.058) | 0.006 | 1.2 (0.4 to 2.0) | 0.002 |
| BRF + stair-climbing score | 0.731 | 0.030 (0.004 to 0.056) | 0.023 | 1.6 (0.9 to 2.4) | <0.001 |
| BRF + speed score | 0.731 | 0.030 (0.007 to 0.053) | 0.012 | 1.1 (0.5 to 1.8) | 0.001 |
| BRF + all 3 scores | 0.741 | 0.040 (0.011 to 0.068) | 0.006 | 1.8 (1.0 to 2.7) | <0.001 |
| Cardiovascular mortality | |||||
| BRF | 0.752 | ref | ref | ref | ref |
| BRF + distance score | 0.797 | 0.045 (−0.004 to 0.094) | 0.073 | 0.9 (−0.1 to 1.8) | 0.083 |
| BRF + stair-climbing score | 0.821 | 0.070 (0.026 to 0.113) | 0.002 | 1.8 (0.8 to 2.8) | <0.001 |
| BRF + speed score | 0.819 | 0.067 (0.024 to 0.110) | 0.002 | 0.7 (−0.2 to 1.6) | 0.108 |
| BRF + all 3 scores | 0.832 | 0.080 (0.034 to 0.126) | 0.001 | 1.8 (0.7 to 2.8) | 0.001 |
BRF indicates baseline risk factors; ΔC, change in C-index from the baseline risk factors model; C, C-index; CI, confidence interval; IDI, integrated discrimination improvement; and ref, reference.
*
C-index for all models was significantly >0.5 at P<0.001.
†
Age, sex, race, smoking history, body mass index, systolic blood pressure, use of lipid-lowering medication, use of antihypertensive medication, diabetes mellitus status, total cholesterol, high-density lipoprotein-cholesterol, and ankle-brachial index.