| Comorbidity measures (CM) | Observational studies | Retrospective, insurance database studies | Registries | Mixed methods |
|---|---|---|---|---|
| Mean (SD) or prevalence n (%) | ||||
| American Society of Anesthesiologists (ASA 0-5) | 2.23 [89] | 2.27 (range 1-3.5) [105] | - | - |
| Cumulative Illness Rating Scale (CIRS, 0-52 or 0-56) | 9.3 (3.8), [82] 3.0 (range 0-10.9), [87] 4.5 (3.4) [88] |
4.8 (4.9), [91] 4.8 (4) [36] |
- | - |
| Charlson Comorbidity Index (CCI, 0-31) | 1.2 (1.2) [88] | - | - | - |
| Functional Comorbidity Index (FCI, 0-18) | 3.2 (1.3) [88] | - | - | - |
| Gagne score (-2-26) | - | 0.48 (1.41) [55] | - | |
| Comorbidities/patient | 2 (3) [88] | 2.85 (1.84), [57,99] 2.78 (1.58), [101] 2.55 (1.11), [39] 1.75 (range 0-4) [105] |
- | - |
| CIRS (0-56), median [range] | 8 [4.8] [84] | - | - | - |
| Comorbidities/patient, median [range] | 5.5 [0.7] [48] | - | - | - |
| Patients with ASA score ≥3 | 29 (28.7), [24] 25 (8) [87] |
74 (62.7), [78] 1192 (50.6), [80] 33 (11), [57,99,101] 23 (18.5), [39] 19 (6.7), [102] 58 (27.6), [77] 125 (58.1) [56] |
1135 (23.8), [23] 106 (48), [33] 999 (22.2) [34] |
- |
| Patients with CCI or modified CCI (mCCI or Quan Comorbidity score, 0-31 or 0-3+) score ≥3 | - | 2358 (7.3), [8] 1756 (6.1), [17] 343 (1.2) [79] |
- | - |
| Patients with CCI ≥2 | - | - | - | 72 (39.6) [45] |
| Patients with Elixhauser index ≥3 | 751 (13.94) [37] | |||
| Patients with any comorbid illnesses | 59 (60.8), [74] 54 (34.2) [94] |
8338 (75.6) [60] | 2544 (33.3) [47] | - |
| Patients with ≥3 comorbidities | 74 (38.1) [38] | 49744 (10.6), [35] 138 (48.8), [102] 78 (36.3) [56] |
- | - |
| Patients with ≥5 comorbidities | 55 (53.9) [40] | - | - | - |
Abbreviations: SD, standard deviation; n (%), number of patients (%)