Related Experiment Video
Updated: Aug 18, 2026

Adult and Pediatric Porcine Model of Acute Volume Overload
Published on: January 12, 2024
Conventional models overestimate the statistical significance of volume-outcome associations, compared with
David R Urbach1, Peter C Austin
1Institute for Clinical Evaluative Sciences, University of Toronto, G Wing Room 140, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada. david.urbach@ices.on.ca
Objective:
To compare the use of conventional statistical models with multilevel regression models in volume-outcome analyses of surgical procedures in an empirical case study.
Study Design And Setting:
Using conventional regression models and multilevel regression models, we estimated the effect of hospital volume and surgeon volume on 30-day mortality and length of postoperative hospital stay in persons who had an esophagectomy, pancreaticoduodenectomy, or major lung resection for cancer in Ontario, Canada, from 1994 to 1999.
Results:
The point estimates of volume-outcome associations were similar using either method; however, the 95% confidence intervals estimated by multilevel models were wider than those estimated by conventional models. A significant association between volume and mortality was identified in 2 of 18 (11%) comparisons using conventional analysis but in none of the 18 (0%) comparisons using multilevel analysis, and between volume and length of stay in 15 of 18 (83%) comparisons using conventional analysis and in 1 of 18 (6%) comparisons using multilevel analysis.
Conclusion:
Conventional and multilevel statistical models can yield substantially different results in the analysis of volume-outcome associations for surgical procedures.
Related Concept Videos
Mechanistic Models: Compartment Models in Individual and Population Analysis
Confounding in Epidemiological Studies
Multicompartment Models: Overview
These models offer a more comprehensive representation of drug behavior in the body than one-compartment models. They accommodate the complexity of drug distribution,...
Mechanistic Models: Overview of Compartment Models
Pharmacokinetic Models: Comparison and Selection Criterion
Physiological models take a detailed approach by considering specific molecular processes. They can predict drug distribution, metabolism, and elimination changes, providing a comprehensive understanding of how drugs interact with the body.
Dose Response Curve: Conventional Versus Nonmonotonic
