RT Journal Article
SR Electronic
T1 Case-mix adjustment in non-randomised observational evaluations: the constant risk fallacy
JF Journal of Epidemiology and Community Health
JO J Epidemiol Community Health
FD BMJ Publishing Group Ltd
SP 1010
OP 1013
DO 10.1136/jech.2007.061747
VO 61
IS 11
A1 Jon Nicholl
YR 2007
UL http://jech.bmj.com/content/61/11/1010.abstract
AB Observational studies comparing groups or populations to evaluate services or interventions usually require case-mix adjustment to account for imbalances between the groups being compared. Simulation studies have, however, shown that case-mix adjustment can make any bias worse.One reason this can happen is if the risk factors used in the adjustment are related to the risk in different ways in the groups or populations being compared, and ignoring this commits the “constant risk fallacy”.Case-mix adjustment is particularly prone to this problem when the adjustment uses factors that are proxies for the real risk factors.Interactions between risk factors and groups should always be examined before case-mix adjustment in observational studies.