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. 2015 Feb 6;107(3):dju491. doi: 10.1093/jnci/dju491

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.