Table 1 Summary of differences between the seven comorbidity scores used

Updated CCI

(15)

12 conditions

Based on 1-year-all-cause mortality

Sum of weighted indices (derived based on hazards ratios)

Updated by Quan et al. (15)

0 to 24

CCI-lung

(16)

10 conditions

Based on the impact on 2-year non-cancer mortality

Sum of weighted indices (derived based on hazards ratios)

0 to 15

ACCI

(17)

12 conditions

Based on 1-year-all-cause mortality

Age-adjusted CCI is equal to the CCI score but 1 point has to be added for each decade above 50 years

CCI + 1 point added for each decade above 50 years old

NCI

(1)

14 conditions

Based on the impact on 2-yr non-cancer mortality

Sum of weighted indices (derived from hazards ratios, available on the NCI website)

0 to 21.14

NCI-lung

(16)

13 conditions

Based on the impact on 2-yr non-cancer mortality

Sum of weighted indices (derived from beta coefficients)

-0.143 to 4.243

Updated Elixhauser

(19)

21 conditions

Used initially as a count (30 conditions) but modified by Van Walraven et al. Based on in-hospital mortality as the sum of the weighted score (hazards ratios derived from beta coefficients divided by the coefficient in the model with the smallest absolute value) (19)

-19 to 89

Elixhauser-lung

(20)

16 conditions

Based on the impact on 2-yr non-cancer mortality

Sum of the weighted indices (derived from the beta coefficient x 10)

-2 to 28