Table 5.
Variance decomposition statistics by injury severity
| Hospital ICC (95% CI) |
Neighbourhood ICC (95% CI) |
Residual ICC (95% CI) |
Patients (n) | |
| Less severe injuries (ISS≤15)* | ||||
| Mortality, unadjusted | 12.3% (7.2 to 16.8) | 0.4% (0.1 to 0.6) | 87.3% (82.7 to 92.6) | 378 788 |
| Mortality, adjusted for casemix | 9.5% (5.6 to 13.1) | 0.1% (−0.1 to 0.3) | 90.4% (86.7 to 94.4) | 371 287 |
| Length of stay, unadjusted | 16.6% (11.3 to 21.3) | 0.2% (0.1 to 0.2) | 83.2% (78.4 to 88.5) | 363 469 |
| Length of stay, adjusted for casemix | 13.4% (9.0 to 17.4) | 0.1% (0.06 to 0.1) | 86.5% (82.5 to 90.9) | 356 467 |
| Total charges, unadjusted | 33.4% (22.6 to 41.6) | 0.1% (0.08 to 0.2) | 66.5% (58.2 to 77.3) | 253 507 |
| Total charges, adjusted for casemix | 30.3% (20.3 to 38.2) | 0.3% (0.2 to 0.4) | 69.4% (61.5 to 79.5) | 250 555 |
| More severe injuries (ISS>15)† | ||||
| Mortality, unadjusted | 4.8% (1.2 to 8.0) | 0.4% (−0.2 to 1.1) | 94.8% (90.9 to 99.0) | 25 887 |
| Mortality, adjusted for casemix | 4.3% (0.9 to 7.4) | 0.6% (−0.1 to 1.3) | 95.1% (91.3 to 99.3) | 25 883 |
| Length of stay, unadjusted | 19.7% (12.0 to 26.4) | 1.5% (0.9 to 2.2) | 78.9% (72.0 to 86.8) | 23 417 |
| Length of stay, adjusted for casemix | 17.0% (9.9 to 23.3) | 0.1% (0.06 to 1.6) | 81.9% (75.5 to 89.3) | 23 414 |
| Total charges, unadjusted | 17.2% (9.5 to 24.1) | 0.1% (0.04 to 1.6) | 81.8% (74.8 to 89.8) | 16 309 |
| Total charges, adjusted for casemix | 13.5% (7.2 to 19.2) | 0.5% (0.1 to 0.8) | 86.0% (80.2 to 92.5) | 16 306 |
*Hospital, n=66; Zip code, n=214.
†Hospital, n=64; Zip code, n=212.
Unadjusted models include random effects only. Adjusted models include fixed effects for patient age, ISS, mechanism of injury and number of patient comorbidities.
ICC, intraclass correlation coefficient; ISS, Injury Severity Score.