Comparing Charlson and Elixhauser comorbidity indices with different weightings to predict in-hospital mortality: an analysis of national inpatient data

Table 3 Comparison of Swiss weights model with Base, Charlson and VW weights models based on the Net Reclassification Improvement (NRI)

Derivation group
Comparison models	NRI (95% CI)	Mortality increased Pr (Up\|Case)	Alive increased Pr (Up\|Ctrl)	Mortality decreased Pr (Down\|Case)	Alive decreased Pr (Down\|Ctrl)
Swiss weights vs. Base model	0.355 (0.352–0.357)	0.448 (0.445–0.450)	0.074 (0.074–0.074)	0.134 (0.133–0.136)	0.115 (0.115–0.116)
Swiss weights vs. Charlson weights model	0.049 (0.044–0.052)	0.297 (0.294–0.299)	0.058 (0.058–0.059)	0.251 (0.250–0.253)	0.062 (0.061–0.062)
Swiss weights vs. VW weights model	0.016 (0.013–0.020)	0.157 (0.155–0.159)	0.021 (0.021–0.022)	0.143 (0.140–0.145)	0.023 (0.023–0.024)

Abbreviations: NRI Net Reclassification Improvement with classification cut-off 0.023, CI confidence interval
Pr (Up, Down) | (Case, Ctrl) represents the proportion of patients whose predicted probabilities increased or decreased for in-hospital mortality and alive cohorts respectively
NRI = (Pr (Up|Case) - Pr (Down|Case)) + (Pr (Down|Ctrl) - Pr (Up|Ctrl))
Base model: age group, sex, hospital types
Charlson weights model: base and Charlson weights
VW weights model: base and Elixhauser/ van Walraven weights
Swiss weights model: base and Elixhauser/ Swiss weights

ISSN: 1472-6963