Background When chronic conditions are associated with outcomes such as mortality, comorbidity measures are essential both to describe patient health status and to adjust for potential confounding. The Charlson and Elixhauser comorbidity indices are well-established for risk adjustment and mortality prediction. Still, as optimal comorbidity weightings remain undetermined. The present study aimed to derive a set of new population-based Elixhauser comorbidity weightings, then to validate and compare their mortality predictivity against those of the Charlson and Elixhauser-based van Walraven weightings estimates in a population-based cohort.
Methods Retrospective analysis was conducted with routine Swiss general hospital (102 hospitals) data (2012–2017) for 6.09 million inpatient cases. To derive the population-based weightings for the Elixhauser comorbidity index, we randomly halved the inpatient data and validated the results for Part 1 alongside the established weighting systems used for Part 2. Charlson and van Walraven weightings were applied to Charlson and Elixhauser comorbidity indices. Generalized additive models were weighted and adjusted for age, gender and hospital types.
Results Overall, the population-based weights’ c-statistic (0.867, 95% CI: 0.865–0.868) was consistently higher than Elixhauser-van Walraven’s (0.863, 95% CI: 0.862–0.864) and Charlson’s (0.850, 95% CI: 0.849–0.851) in the derivation and validation groups and net reclassification improvement of new weights offers improved predictive performance of 0.4% on the Elixhauser-van Walraven and 6.1% on the Charlson weightings.
Conclusions All weightings were validated with the national dataset and the new population-based weightings model improved the prediction of in-hospital mortality. The newly derive weights support patient population-based analysis of health outcomes.

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On 08 Jul, 2020
On 08 Jul, 2020
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On 07 Jul, 2020
On 26 Jun, 2020
On 08 Dec, 2020
On 03 Dec, 2020
Received 15 Nov, 2020
On 15 Nov, 2020
Received 04 Nov, 2020
On 31 Oct, 2020
On 26 Oct, 2020
Invitations sent on 26 Oct, 2020
On 26 Oct, 2020
On 25 Oct, 2020
On 25 Oct, 2020
On 26 Sep, 2020
Received 25 Sep, 2020
Received 14 Sep, 2020
On 03 Sep, 2020
On 02 Sep, 2020
On 01 Sep, 2020
Invitations sent on 01 Sep, 2020
On 31 Aug, 2020
On 31 Aug, 2020
Posted 14 Jul, 2020
Received 31 Jul, 2020
On 31 Jul, 2020
Received 31 Jul, 2020
Received 27 Jul, 2020
Received 25 Jul, 2020
Received 24 Jul, 2020
On 14 Jul, 2020
On 13 Jul, 2020
On 10 Jul, 2020
On 08 Jul, 2020
Invitations sent on 08 Jul, 2020
On 08 Jul, 2020
On 08 Jul, 2020
On 07 Jul, 2020
On 07 Jul, 2020
On 26 Jun, 2020
Background When chronic conditions are associated with outcomes such as mortality, comorbidity measures are essential both to describe patient health status and to adjust for potential confounding. The Charlson and Elixhauser comorbidity indices are well-established for risk adjustment and mortality prediction. Still, as optimal comorbidity weightings remain undetermined. The present study aimed to derive a set of new population-based Elixhauser comorbidity weightings, then to validate and compare their mortality predictivity against those of the Charlson and Elixhauser-based van Walraven weightings estimates in a population-based cohort.
Methods Retrospective analysis was conducted with routine Swiss general hospital (102 hospitals) data (2012–2017) for 6.09 million inpatient cases. To derive the population-based weightings for the Elixhauser comorbidity index, we randomly halved the inpatient data and validated the results for Part 1 alongside the established weighting systems used for Part 2. Charlson and van Walraven weightings were applied to Charlson and Elixhauser comorbidity indices. Generalized additive models were weighted and adjusted for age, gender and hospital types.
Results Overall, the population-based weights’ c-statistic (0.867, 95% CI: 0.865–0.868) was consistently higher than Elixhauser-van Walraven’s (0.863, 95% CI: 0.862–0.864) and Charlson’s (0.850, 95% CI: 0.849–0.851) in the derivation and validation groups and net reclassification improvement of new weights offers improved predictive performance of 0.4% on the Elixhauser-van Walraven and 6.1% on the Charlson weightings.
Conclusions All weightings were validated with the national dataset and the new population-based weightings model improved the prediction of in-hospital mortality. The newly derive weights support patient population-based analysis of health outcomes.

Figure 1
This is a list of supplementary files associated with this preprint. Click to download.
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