Table 2.
Estimated effect of case volume on annual mortality from open heart operations in children aged <1 year, based on data from the hospital episode statistics and the cardiac surgical register
| Adjustment for type of operation (excluding influence of Bristol) | Estimated change (%) in risk for each additional patient | Baseline mortality (%) in a hospital treating 40 children | Predicted mortality (%)
|
|
|---|---|---|---|---|
| 80 children | 120 children | |||
| No adjustment | −0.4 | 15.0 | 13.0 | 11.3 |
| Adjustment | −0.6 | 15.0 | 12.2 | 9.9 |
A change in risk of −0.6% means that each additional patient a year is expected to change the odds of death by a factor of 0.994; hence 40 extra patients reduces the odds of death by a factor of (0.994)40 = 0.79.