Journal article
Modeling mortality risk in hemodialysis patients using laboratory values as time-dependent covariates
American journal of kidney diseases, Vol.28(5), pp.741-746
11/1996
DOI: 10.1016/S0272-6386(96)90258-9
PMID: 9158214
Abstract
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. Additionally, the predictive values of the time-dependent covariates ALB and CR affirm the significance of nutritional approaches directed toward maintaining visceral and somatic protein content throughout renal replacement therapy.
Details
- Title: Subtitle
- Modeling mortality risk in hemodialysis patients using laboratory values as time-dependent covariates
- Creators
- Kennith Culp - University of Iowa, NursingMichael Flanigan - University of Iowa, Internal MedicineEdmund G. Lowrie - College of Nursing and the Department of Preventive Medicine and Environmental Health, The University of Iowa, Iowa City, IA, USANancy Lew - College of Nursing and the Department of Preventive Medicine and Environmental Health, The University of Iowa, Iowa City, IA, USABridget Zimmerman - University of Iowa
- Resource Type
- Journal article
- Publication Details
- American journal of kidney diseases, Vol.28(5), pp.741-746
- DOI
- 10.1016/S0272-6386(96)90258-9
- PMID
- 9158214
- NLM abbreviation
- Am J Kidney Dis
- ISSN
- 0272-6386
- eISSN
- 1523-6838
- Publisher
- Elsevier Inc
- Number of pages
- 6
- Language
- English
- Date published
- 11/1996
- Academic Unit
- Biostatistics; Nursing; Internal Medicine
- Record Identifier
- 9983997355002771
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