Survival Percentile and Predictors of Difference in Survival among Hemodialysis Patients and Their Additive Interaction Using Laplace Regression

Background: Identifying survival modifiable factors and additive interaction between them could help in prioritizing the clinical care of Hemodialysis (HD) patients. We aimed to examine the survival rate and its predictors in HD patients; and explore the additive interaction between survival modifiable factors. Study design: A retrospective cohort study. Methods: The present study was performed on 1142 HD patients in Hamadan Province, western Iran from 2007 to 2017. Data were collected through a researcher-made checklist on hospital records. Laplace regression was used to evaluate differences in 40(th) survival percentiles in different levels of predictors as well as exploring the pairwise additive interactions between variables. Results: We observed significantly higher survival in nonsmoker patients (40(th) percentile difference = 5.34 months, 95% CI: 2.06, 8.61). Survival was shorter by more than 3 years in CRP positive patients (40(th) percentile difference=36.9 months, 95% CI: 32.37, 41.42). Patients with normal albumin (40(th) percentile difference =24.92, 95% CI: 18.04, 31.80) and hemoglobin (40(th) percentile difference = 18.65, 95% CI: 12.43, 24.86) had significantly higher survival (P<0.001). There was super-additive interaction between being CRP negative and nonsmoker (β(3) = 9.42 months, 95% CI: 3.35, 15.49 (P=0.002)). Conclusion: High CRP and low serum albumin and hemoglobin were associated with the increased risk of death in HD patients. The results of this study support the presence of super-additive interaction between CRP status with serum hemoglobin and also CRP status with smoking, resulting in excess survival in HD patients.