Proportional hazards analyses assume that the magnitude of mortality risk for a predictor variable remains proportional over time.
In a time-dependent model, the explanatory variable violates this assumption, and repeat observations are required to accommodate the change in risk that occurs over time.
Using a retrospective cohort design, we tested the following laboratory values for a time-by-covariate interaction : hematocrit (HCT), serum albumin (ALB), and serum creatinine (CR).
A random sample of 4,083 hemodialysis patients whose specimens were analyzed in a central laboratory over a 3-year period served as the study group.
Using the baseline observation, we discovered significant probability values for the interaction terms TIME*CR (P=0.013) and TIME*ALB (P<0.01).
The beta coefficient for TIME*HCT was not significant, indicating that the proportional hazard assumption was not violated by this covariate.
Based on these results, we fitted a multivariate regression model containing two time-dependent covariates (CR and ALB) using a data structure that incorporated repeat observations of these laboratory values.
Patients with high ALB levels experienced the lowest mortality risk.
Similarly, serum CR levels were higher in long-term survivors.
This analysis verifies the clinical importance of monitoring ALB and CR levels over time and the hazard of using a single laboratory observation to make long-term projections. (...)
Mots-clés Pascal : Hémodialyse, Evaluation, Facteur risque, Mortalité, Modélisation, Hématocrite, Albumine, Créatinine, Sérum, Etude statistique, Homme, Epuration extrarénale, Appareil urinaire pathologie, Rein pathologie, Insuffisance rénale
Mots-clés Pascal anglais : Hemodialysis, Evaluation, Risk factor, Mortality, Modeling, Hematocrite, Albumin, Creatinine, Serum, Statistical study, Human, Extrarenal dialysis, Urinary system disease, Kidney disease, Renal failure
Notice produite par :
Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 97-0033947
Code Inist : 002B27B03. Création : 21/05/1997.