MO895: Comorbidity or Frailty, Which One Has a Greater Impact on Early Mortality in Incident Elderly Dialysis Patients?
Authors: Fernandes João , Fraga Dias Bruno , Sala Inês , Freitas Joana , Santos Lascasas Josefina , Malheiro Jorge , Cabrita António 
Published: May 2022

Abstract

BACKGROUND AND AIMS
Mortality in end-stage renal disease remains high, especially among the elderly with a higher burden of comorbidity and frailty. In this group, dialysis (HD) may not offer better survival compared with conservative management. Frailty defined by clinical frailty scale (CFS) and comorbidity by modified Charlson Comorbidity Index (mCCI) are known independent predictors of mortality. Our aim is to compare that has higher impact on early mortality in incident elderly HD patients.

METHOD
We conducted a retrospective cohort study of patients aged 65 years and over, who started HD as their first renal replacement therapy (RRT) between January 2014 and December 2019. CFS and mCCI, at time of HD start, were used to evaluate, respectively, frailty and comorbid disease burden. The primary outcome was death in the first 6 months of RRT. The optimal cut-off for our outcome was defined through the analysis of a receiver operating characteristic (ROC) curve. Survival curves were constructed using Kaplan–Meier method, with comparison between patients' groups being done by log-rank test. Multivariable Cox analysis was applied to assess independent predictors of early mortality. All p values are two-tailed, p value &lt; 0.05 is considered to indicate statistical significance.

RESULTS
166 patients were included, 107 (64%) started HD by central venous catheter. The median age, at time of haemodialysis start, was 75 years ± 6.3 years. The mortality at 6 months was 19% (n = 31). For both scales, the analysis of ROC curve, stablished the optimal cut-off to predict the event death at first 6 months of HD as ≥ 5points. The performance of CFS was superior to the mCCI (P = 0.031; Figure 1 top). In fact, the area under the curve is higher in CFS (0.739) versus the mCCI (0.620). A CFS ≥ 5 had a sensitivity/specificity of 94%/44% in prediction the primary outcome. On the other and, a mCCI ≥ 5 predicts the same outcome with a sensitivity/specificity of 26%/88%. The diagnostic odds ratio for CFS ≥ 5 was 11.6, compared with only 2.7 for mCCI ≥ 5. When confronted using the Kaplan–Meier method, both CSF &lt; 5 versus CSF ≥ 5 and mCCI &lt; 5 versus mCCI ≥ 5 presented different survival rates that proved to be statistically significant by log rank test (P &lt; 0.001 and P = 0.020, respectively; Figure 1 medium and bottom). CFS was an independent predictor of 6 month mortality both as a categorical (CSF ≥ 5) (HR = 3.64; P = 0.004) and continuous variable (HR = 1.95; P &lt; 0.01). mCCI didn't prove to be an independent predictor. Lastly, we constructed a model in which both scores interacted (as categorical variables), in this multivariable adjusted model mCCI/CFS &lt; 5/≥5 and ≥ 5/≥5 were intendent predictors of mortality (HR = 6.141; P = 0.022) (HR = 10.58; P = 0.002). Interestingly, no events were observed in the mCCI ≥ 5/CFS &lt; 5 group.

CONCLUSION
In this cohort of incident elderly HD patients, frailty defined by CFS was a stronger predictor of mortality than comorbidity defined by CCI. The group of mCCI/CFS (≥5/≥5) has a 10-time higher chance of dying than the reference group. Our data also suggest that simple scores can predict the risk of early mortality in incident HD patients and should be used to guide the decision-making process for elderly patients and to improve the quality of the information given to patients and families.