Combining Charlson and Elixhauser scores with varying lookback predicated mortality better than using individual scores

Abstract

Objective: To investigate variation in the presence of secondary diagnosis codes in Charlson andElixhauser comorbidity scores and assess whether including a one-year lookback period improved prognostic adjustment by these scores individually, and combined, for 30-day mortality. Study Design and Setting:We analysed inpatient admissions from 01-Jan-2007 to 18-May-2018 in Oxfordshire, UK. Comorbidity scores were calculated using secondary diagnostic codes in the diagnostic-dominant episode, and primary and secondary codes from the year before. Associations between scores and 30-day mortality were investigated using Cox models with natural cubic splines for non-linearity, assessing fit using Akaike Information Criteria. Results:The one-year lookback improved model fit for Charlson and Elixhauser scores vs using diagnostic-dominant methods. Including both, and allowing non-linearity, improved model fit further. The diagnosis-dominant Charlson score and Elixhauser score using a 1-year lookback, and their interaction, provided the best comorbidity adjustment (reduction in AIC: 761 from best single score model). Conclusion:The Charlson and Elixhauser score calculated using primary and secondary diagnostic codes from 1-year lookback with secondary diagnostic codes from current episode improved individual predictive ability. Ideally, comorbidities should be adjusted for using both the Charlson (diagnostic-dominant) and Elixhauser (one-year lookback) scores, incorporating non-linearity and interactions for optimal confounding control.

Study protocol for a national observational cohort investigating frailty, delirium and multimorbidity in older surgical patients: the third Sprint National Anaesthesia Project (SNAP 3)

“…Multimorbidity is assessed through a list of relevant comorbidities which has been derived from the Charlson Comorbidity Index and a priori knowledge of comorbidities relevant to older patients with frailty and at risk of delirium 59. The Elixhauser Comorbidity Index will be calculated from HES data (or equivalent) following the method of Pritchard et al including a 1-year look back 60…”

“… 59 The Elixhauser Comorbidity Index will be calculated from HES data (or equivalent) following the method of Pritchard et al including a 1-year look back. 60 …”

“…59 The Elixhauser Comorbidity Index will be calculated from HES data (or equivalent) following the method of Pritchard et al including a 1-year look back. 60 Participants who remain inpatients on days 3 and 7 will be assessed for postoperative morbidity using an appropriate specialty specific POMS and either the 4AT (if not critically ill) or CAM-ICU (if critically ill). 44-47 61 Delirium and postoperative morbidity will be assumed absent for those discharged alive on the day of surgery.…”

Combining the Hospital Frailty Risk Score With the Charlson and Elixhauser Multimorbidity Indices to Identify Older Patients at Risk of Poor Outcomes in Acute Care

“…[27][28][29] The aim of this study was to establish whether the HFRS is able to discriminate patients with the risks of poor outcomes among hospitalized older patients over and above the Charlson 27 and Elixhauser 29 multimorbidity indices. Also, in the same way that combining comorbidity indices might improve the accuracy of risk stratification, 30,31 we sought to explore possible combinations and overlaps of the HFRS with these multimorbidity indices.…”