Ii N = 249,744 for LOS Analysis, N = 238,999 for 30-Day Mortality Analysis

Supplementary Table 1. Validation studies of CCI adaptations

Author & Study Population and data source Baseline Model CCI Adaptation Prediction of Primary Outcome Year D’Hoore Hospitalized patients with ischemic heart Age + Gender + In-hospital mortality 1993(11) disease, CHF, stroke or bacterial pneumonia Principal Diagnosis D’Hoore CCI c = 0.83 (N = 62,456), MED-ECHO database, + Hospital Care Quebec, 1989-1990 Melfi Medicare Hospitalization data from TKR Age + Gender + 30-day LOS 1995(12) surgery patients, 1985-1989 Race + Type of Mortality (N = 249,744) Arthritis Baseline c = 0.645 R2 = 0.1703 Deyo CCIc c = 0.653 R2 = 0.1743 No. of Diagnoses c = 0.733 R2 = 0.2106 Poses Hospitalization data from a prospective cohort Each parameter, In-hospital mortality 1995(13) of patients with suspected bacteremia in a e.g. age, analyzed c-statistic OR 95% CI p university hospital, Virginia, 1984-1995. (N separately (no Age 0.61 1.02 [1.00, 1.04 0.05 = 227) baseline model) Time in hospital 0.62 1.02 [1.0, 10.4] 0.03 Deyo CCI 0.64 1.2 [1.1, 1.4] 0.001 APACHE II 0.83 1.3 [1.2, 1.4] <0.0001

Ghali Hospitalization discharge abstract data from Age + Gender In-hospital mortality 1996(14) patient s with CABG surgery, Massachusetts c-statistic 95% CI R2 Health Data Consortium 1992 (N = 6791) Baseline 0.661 0.656, 0.661 0.013 Deyo CCI 0.704 0.696, 0.705 0.018

Ghali CCIinteger 0.739 0.736, 0.740 0.034 Ghali CCIcoefficents 0.757 0.755, 0.757 0.041 D’Hoore Hospitalization data from MED-ECHO, Age + Gender + D’Hoore CCI In-hospital mortality 1996(15) Quebec, hospitalized patients with ischemic Principal Diagnosis c = 0.87 heart disease, 1989-90 (N = 33,940) Roos 1997(16) Hospitalization data, Manitoba Health, Age + Gender 1-year mortality patients with CABG (n = 1,558), pacemaker Original Romano Augmented Romano surgery (n = 1,645) or hip fracture repair (n = CABG + Romano c = 0.64 c = 0.68 3,984), 1990-94. CCI PSa + Romano CCI c = 0.70 c = 0.77 HFR + Romano CCI c = 0.75 c = 0.76 Cleves Medicare Part A hospital claims data, Age + Gender 30-day 90-day 180- day mortality 1997(17) Arkansas, all admissions 1993-94 (N = NR) c-statistic c-statistic c-statistic Baseline 0.59 – 0.74 0.62 – 0.69 0.62 – 0.66 Deyo CCI 0.60 – 0.75 0.64 – 0.74 0.65 – 0.74

Deyo CCIEW 0.62 – 0.79 0.65 – 0.75 0.66 – 0.75 Romano CCI 0.61 – 0.74 0.65 – 0.75 0.66 – 0.77

Romano CCIEW 0.62 – 0.77 0.66 – 0.75 0.67 – 0.78 Librero Hospitalization data, all admissions aged ≥ Age + Gender Study-specific CCI 1-year readmission 1999(18) 16, from 12 Valencia Health Service c = 0.58 OR = 1.43 (95% CI: 1.26, 1.63) hospitals, , Spain, 1993 (N = 97,430)

Wang 2000 Medicaid, Medicare, and PAAD Age + Gender + 1-year mortality (19) hospitalization and outpatient data for all Race + SES + Year c-statistic OR 95% CI women aged ≥ 20 , , New Jersey, 1989-91 (N of Diagnosis Baseline 0.668 = 3994) Deyo CCI + Index 0.711 1.17 1.13, 1.21 Deyo CCI + Prior IP 0.695 1.22 1.16, 1.28 Deyo CCI + Prior OP 0.669 1.05 0.98, 1.12 Deyo CCI + All 0.719 1.18 1.14, 1.22 Source Klabunde Hospitalization and outpatient data, men with Age + Race + Prediction of treatment 2000(20) prostate cancer (n = 28,868) and women with Tumor stage or c-statistic OR 95% CI breast cancer (n = 14,943) from National grade + SES Study Specific CCI + 0.82 2.51* 1.90, 3.32 Cancer Institute’s SEER program linked to +Geographic Prostate Cancer 2.13** 1.66, 2.73 Medicare Part A and B claims, 1992-93 Region +Education Population Study Specific CCI + 0.74 1.88* 1.52, 2.33 Breast Cancer 1.30** 1.07, 1.56 Population Sundararajan Hospitalization data from the Victorian NR In-hospital mortality 2004(21) Admitted Episodes Dataset, all Victoria State c = 0.86 hospitals, Australia, 1997-99 (N = 400,000) Deyo CCI (ICD-9-CM) Deyo CCI (ICD-10-AM) c = 0.85 Deyo CCI (ICD-9-CM) c = 0.80 Deyo CCI (ICD-10-AM) c = 0.80 Harse Hospitalization data, patients with hip or Age + Gender + Change in SF-36 Following Surgery 2005(22) knee replacement surgery, Western Australia Surgery Type + Baseline R2 = 11.78% hospital Insurance Type + 1 year LB Romano CCI R2 = 11.78% + 1.02% Age x Gender 1 year LB Binary Romano CCI R2 = 11.78% + 1.79% Interaction Term 5 year LB Romano CCI R2 = 11.78% + 1.18 5 year LB Binary Romano CCIc R2 = 11.78% + 1.11 Holman Hospitalization data from Western Australia Age + Gender + 1-year 30-day re- LOS 2005(23) hospitals. Race + SES mortality admission Index development cohort: all hospital c-statistic c-statistic R2 admissions 1989-96 CCI 0.88 – 0.74 0.67 – 0.61 0.167 – 0.027 (N = 1,118,989) MACSS 0.90 – 0.81 0.77 – 0.64 0.332 – 0.127 Abbreviations; CCI indicates Charlson Comorbidity Index; CHF, Congestive Heart Failure; NR, Not reported; TKR, Total Knee Replacement; LOS, length of stay; PM, Pacemaker Sugery; HFR, Hip Fracture Repair; SES, Socioeconomic Status; CABG, coronary artery bypass grafting; APACHE, Acute Physiology and Chronic Health Evaluation; PAAD, pharmacy assistance for the aged and disabled; SEER, Surveillance, Epidemiology and End Results; HRQOL, Health Related Quality of Life; AMI; Acute Myocardial Infarction; TURP, transurethral resection of prostate, MDD, major depressive disorder; ICU, intensive care unit; MedPar, Medicare Provider Analysis and Review; GPRD, General Practice Research Database; ESRD, End Stage Renal Disease