Table 2.
Performance of the SMR Models in Derivation and Validation Cohorts
| Model and Cohort | N | Mortality, N (%) | C stat | H-L GOF chi-square | Brier’s score |
|---|---|---|---|---|---|
| Acute Care SMR-30 derivation | 769710 | 33180 (4.31) | 0.871 | 187.7 | 0.035 |
| Acute Care SMR-30 validation, full year | 373791 | 16036 (4.29) | 0.870 | 211.6 | 0.035 |
| Acute Care SMR-30 validation, Q1 | 92338 | 4038 (4.37) | 0.871 | 39.1 | 0.035 |
| Acute Care SMR-30 validation, Q2 | 94640 | 4258 (4.50) | 0.869 | 49.1 | 0.037 |
| Acute Care SMR-30 validation, Q3 | 95269 | 4023 (4.22) | 0.867 | 66.3 | 0.034 |
| Acute Care SMR-30 validation, Q4 | 91544 | 3717 (4.06) | 0.873 | 88.4 | 0.033 |
| ICU SMR-30 derivation | 151426 | 13635 (9.00) | 0.871 | 155.3 | 0.063 |
| ICU SMR-30 validation | 72160 | 6638 (9.20) | 0.864 | 110.6 | 0.066 |
| ICU SMR-30 validation, ICU level 1/2 | 62806 | 5746 (9.15) | 0.866 | 103.0 | 0.065 |
| ICU SMR-30 validation, ICU level 3/4 | 9354 | 892 (9.54) | 0.848 | 18.0 | 0.071 |
| ICU SMR-30 validation, Q1 | 17981 | 1652 (9.19) | 0.864 | 29.3 | 0.066 |
| ICU SMR-30 validation, Q2 | 18704 | 1787 (9.55) | 0.863 | 32.1 | 0.069 |
| ICU SMR-30 validation, Q3 | 18276 | 1681 (9.20) | 0.865 | 36.3 | 0.066 |
| ICU SMR-30 validation, Q4 | 17199 | 1518 (8.83) | 0.862 | 31.8 | 0.064 |
| Acute Care SMR derivation | 853194 | 15429 (1.81) | 0.916 | 247.6 | 0.015 |
| Acute Care SMR validation | 413329 | 7173 (1.74) | 0.914 | 218.6 | 0.015 |
| Acute Care SMR validation, Q1 | 102049 | 1802 (1.77) | 0.918 | 57.8 | 0.015 |
| Acute Care SMR validation, Q2 | 104446 | 1960 (1.88) | 0.911 | 35.4 | 0.016 |
| Acute Care SMR validation, Q3 | 105513 | 1759 (1.67) | 0.912 | 75.0 | 0.014 |
| Acute Care SMR validation, Q4 | 101321 | 1652 (1.63) | 0.914 | 77.6 | 0.014 |
| ICU SMR derivation | 152914 | 9641 (6.30) | 0.895 | 229.7 | 0.046 |
| ICU SMR validation | 72752 | 4555 (6.26) | 0.887 | 153.0 | 0.047 |
| ICU SMR validation, ICU level 1/2 | 63873 | 4122 (6.45) | 0.887 | 128.0 | 0.048 |
| ICU SMR validation, ICU level 3/4 | 8879 | 433 (4.88) | 0.887 | 41.7 | 0.039 |
| ICU SMR validation, Q1 | 18125 | 1138 (6.28) | 0.887 | 23.8 | 0.047 |
| ICU SMR validation, Q2 | 18881 | 1259 (6.67) | 0.886 | 49.4 | 0.050 |
| ICU SMR validation, Q3 | 18451 | 1145 (6.21) | 0.888 | 42.0 | 0.046 |
| ICU SMR validation, Q4 | 17295 | 1013 (5.86) | 0.887 | 61.3 | 0.045 |
ICU, intensive care unit; SMR, standardized mortality ratio; Q, quarter; C stats, C statistic; H-L GOF chi-square, Hosmer Lemeshow goodness-of-fit C statistic chi-square value where a lower value is better and the size of the value is linearly related to the size of the cohort; all HL GOF chi-square values were significantly different (p<0.05). Level 1/2, ICUs who can provide most subspecialty medical and surgical Care; level 3/4: ICUs in smaller hospitals which lack some or many medical and surgical subspecialty care