Table 5.
Sensitivity analyses stratified by volume measurement at both surgeon- and hospital-level*
| Sample | 30-day mortality | 30-day readmission | Length of hospital stay | |||
|---|---|---|---|---|---|---|
| OR† (95% CI) | P‡ | OR (95% CI) | P | IRR (95% CI) | P | |
| Unmatched sample (total n = 45 876) | ||||||
| Low-volume surgeon low-volume hospital (n = 22 612) |
0.54 (0.44 to 0.66) | <.001 | 0.90 (0.79 to 1.02) | .095 | 0.84 (0.82 to 0.86) | <.001 |
| High-volume surgeon low-volume hospital (n = 9112) |
0.52 (0.37 to 0.73) | <.001 | 0.85 (0.71 to 1.03) | .095 | 0.82 (0.80 to 0.85) | <.001 |
| Low-volume surgeon high-volume hospital (n = 7362) |
0.59 (0.40 to 0.86) | <.001 | 0.82 (0.66 to 1.03) | .087 | 0.80 (0.78 to 0.83) | <.001 |
| High-volume surgeon high-volume hospital (n = 6790) |
0.53 (0.33 to 0.85) | <.001 | 0.91 (0.62 to 1.34) | .429 | 0.81 (0.79 to 0.84) | <.001 |
| PS matched sample (total n = 36 460) | ||||||
| Low-volume surgeon low-volume hospital (n = 15 634) |
0.54 (0.43 to 0.67) | <.001 | 0.93 (0.80 to 1.07) | .299 | 0.84 (0.82 to 0.85) | <.001 |
| High-volume surgeon low-volume hospital (n = 8682) |
0.63 (0.43 to 0.90) | .012 | 0.84 (0.70 to 1.02) | .075 | 0.85 (0.83 to 0.88) | <.001 |
| Low-volume surgeon high-volume hospital (n = 5648) |
0.54 (0.36 to 0.83) | .004 | 0.91 (0.71 to 1.16) | .434 | 0.81 (0.78 to 0.84) | <.001 |
| High-volume surgeon high-volume hospital (n = 6496) |
0.60 (0.36 to 0.98) | .040 | 1.27 (0.98 to 1.64) | .069 | 0.83 (0.81 to 0.86) | <.001 |
* All statistical tests were two-sided. CI = confidence interval; IRR = incident rate ratio; OR = odds ratio; PS = propensity score.
† Laparoscopic colectomy vs open colectomy. Referent = open colectomy.
‡ P values derived from adjusted multilevel regressions.