Table 4.
Predictive Risks and Reclassification of Total Coronary Heart Disease Events Using a Multivariate Risk Prediction Model With and Without Inclusion of IL-6, AAI, or IL-6 + AAI (n = 1,985), Health, Aging, and Body Composition Study, 1997–2007a
| Predicted 7.5-Year Risk of a CHD Event | No. of Participants, by Predicted 7.5-Year Risk |
No. of Participants Reclassifiedb |
Proportion Correctly Reclassified, %c | 95% Confidence Interval | P Value | |||
| <7.5% | 7.5%–<15% | ≥15% | Increased Risk | Decreased Risk | ||||
| Predicted 7.5-Year CHD Event Risk With IL-6 | ||||||||
| Predicted risk without IL-6 among persons with events during follow-up (n = 313) | ||||||||
| <7.5% | 3 | 2 | 27 | 31 | −1.3 | |||
| 7.5%–<15% | 9 | 83 | 25 | |||||
| ≥15% | 22 | 169 | ||||||
| Predicted risk without IL-6 among persons without events during follow-up (n = 1,672) | ||||||||
| <7.5% | 39 | 19 | 138 | 269 | 7.8 | |||
| 7.5%–<15% | 136 | 648 | 119 | |||||
| ≥15% | 133 | 578 | ||||||
| Net reclassification improvementd | 6.6 | 1.2, 11.9 | 0.016 | |||||
| Predicted 7.5-Year CHD Event Risk With AAI | ||||||||
| Predicted risk without AAI among persons with events during follow-up (n = 313) | ||||||||
| <7.5% | 4 | 1 | 14 | 7 | 2.2 | |||
| 7.5%–<15% | 1 | 103 | 13 | |||||
| ≥15% | 6 | 185 | ||||||
| Predicted risk without AAI among persons without events during follow-up (n = 1,672) | ||||||||
| <7.5% | 49 | 9 | 68 | 85 | 1.0 | |||
| 7.5%–<15% | 30 | 814 | 59 | |||||
| ≥15% | 55 | 656 | ||||||
| Net reclassification improvementd | 3.3 | 0.04, 6.5 | 0.047 | |||||
| Predicted 7.5-Year CHD Event Risk With IL-6 + AAI | ||||||||
| Predicted risk without IL-6 + AAI among persons with events during follow-up (n = 313) | ||||||||
| <7.5% | 3 | 2 | 24 | 40 | −5.1 | |||
| 7.5%–<15% | 13 | 82 | 22 | |||||
| ≥15% | 27 | 164 | ||||||
| Predicted risk without IL-6 + AAI among persons without events during follow-up (n = 1,672) | ||||||||
| <7.5% | 37 | 19 | 2 | 143 | 312 | 10.1 | ||
| 7.5%–<15% | 161 | 620 | 122 | |||||
| ≥15% | 151 | 560 | ||||||
| Net reclassification improvementd | 5.0 | −0.6, 10.6 | 0.080 | |||||
Abbreviations: AAI, ankle-arm index; CHD, coronary heart disease; IL-6, interleukin-6.
Reclassification of CHD risk was evaluated among the 1,985 participants with no missing AAI and IL-6 data by comparing predicted risk estimates based on multivariate models that included age, gender, total and high density lipoprotein cholesterol, systolic blood pressure, smoking, and diabetes, with and without inclusion of IL-6, AAI, or both, for persons with and without CHD events during follow-up (10). Data shown are the numbers of subjects cross-classified by their predicted 7.5-year risk using the models with and without inclusion of IL-6, AAI, or both. The 7.5-year risk was divided into <7.5%, 7.5%–<15%, and ≥15%, which is close to the corresponding 10-year risk of <10%, 10%–<20%, and ≥20% used in national guidelines (18).
Numbers of subjects who were reclassified upwards and downwards, respectively, when IL-6, AAI, or both were added to the model.
Proportion of all participants with CHD events who were “correctly” reclassified into a higher risk category, plus the proportion of all participants remaining event-free who were reclassified into a lower category, minus the proportion of each group reclassified in the “wrong” direction.
Sum of the percentages of correctly reclassified subjects with and without CHD events. Significant P values indicate improved classification (9).