Table 2.
Between-Group Differences in Operative Mortality and Long-Term Mortality For Comparisons of Transfer, Hospital Volume, and Regionalization
| Group Contrast Measure | Transferred vs. Stayed | High-Volume vs. Low-Volume* | Rerouted to High-Volume vs. Not Rerouted to High-Volume† |
||||||
|---|---|---|---|---|---|---|---|---|---|
| Transferred | Stayed | P Value |
High-Volume | Low-Volume | P Value |
Rerouted to High- Volume |
Not Rerouted to High- Volume |
P Value |
|
| Operative Mortality | |||||||||
| Operative mortality - % | 24.8 | 25.5 | - | 22.0 | 29.8 | - | 22.6 | 29.9 | - |
| Absolute risk difference - % (95% CI) | −0.69 (−2.70 to 1.35) | Reference | 0.35 | −8.1 (−10.0 to −6.2) | Reference | <0.001 | −7.2 (−10.3 to −4.1) | Reference | <0.001 |
| Odds ratio (95% CI) | 0.96 (0.87 to 1.07) | Reference | 0.50 | 0.66 (0.60 to 0.73) | Reference | <0.001 | 0.69 (0.58 to 0.81) | Reference | <0.001 |
| Number needed to treat - no. (95% CI) | - | - | - | - | - | - | 14 (10 to 25) | Reference | - |
| Long-Term Mortality | |||||||||
| Mortality at 15 yrs, % | 83.6 | 84.6 | - | 84.1 | 86.6 | - | 84.2 | 85.7 | - |
| Hazard ratio (95% CI) | 1.00 (0.92 to 1.09) | Reference | 0.99 | 0.74 (0.70 to 0.78) | Reference | <0.001 | 0.81 (0.75 to 0.87) | Reference | <0.001 |
| Restricted mean survival time at 15 yrs | |||||||||
| Difference - days (95% CI) | −45.5 (−142.2 to 51.2) | Reference | 0.36 | 288.2 (194.6 to 381.7) | Reference | <0.001 | 213.2 (85.7 to 340.7) | Reference | 0.001 |
| Ratio (95% CI) | 0.98 (0.94 to 1.02) | Reference | 0.36 | 1.14 (1.11 to 1.19) | Reference | <0.001 | 1.11 (1.04 to 1.17) | Reference | 0.001 |
| Ratio of restricted mean time lost (95% CI) | 1.02 (0.98 to 1.05) | Reference | 0.36 | 0.91 (0.88 to 0.94) | Reference | <0.001 | 0.93 (0.89 to 0.97) | Reference | 0.001 |
Gamma = 1.36 for this comparison. The gamma parameter estimates the amount of unmeasured bias necessary to render the finding null. For interpretation, a Gamma = 1.36, implies unobserved covariates would need to increase the odds of presenting at a hospital that would result in care at a low level hospital 2.00-fold, and increase the odds of operative mortality 1.72-fold, to render the presented finding null.
Gamma = 1.28 for this comparison. For interpretation, a Gamma = 1.28, implies unobserved covariates would need to increase the odds of presenting at a non-regionalized hospital 2.00-fold, and increase the odds of operative mortality 1.56-fold, to render the presented finding null.
CI, confidence interval