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Title: Methodological aspects in the assessment of treatment effects in observational health outcomes studies
Authors: Haro, Josep Maria
Kontodimas, Stathis
Negrin, Miguel Angel 
Ratcliffe, Mark
Suarez, David
Windmeijer, Frank
Issue Date: 2006
Publisher: 1175-5652
Journal: Applied Health Economics and Health Policy 
Abstract: Prospective observational studies, which provide information on the effectiveness of interventions in natural settings, may complement results from randomised clinical trials in the evaluation of health technologies. However, observational studies are subject to a number of potential methodological weaknesses, mainly selection and observer bias. This paper reviews and applies various methods to control for selection bias in the estimation of treatment effects and proposes novel ways to assess the presence of observer bias. We also address the issues of estimation and inference in a multilevel setting. We describe and compare the useof regression methods, propensity score matching, fixed-effects models incorporating investigator characteristics, and a multilevel, hierarchical model using Bayesian estimation techniques in the control of selection bias. We also propose to assess the existence of observer bias in observational studies by comparing patient-and investigator-reported outcomes. To illustrate these methods, we have used data from the SOHO (Schizophrenia Outpatient Health Outcomes) study, a large, prospective, observational study of health outcomes associated with the treatment of schizophrenia.The methods used to adjust for differences between treatment groups that could cause selection bias yielded comparable results, reinforcing the validity of the findings. Also, the assessment of observer bias did not show that it existed in the SOHO study. Observational studies, when properly conducted and when using adequate statistical methods, can provide valid information on the evaluation of health technologies.
ISSN: 1175-5652
DOI: 10.2165/00148365-200605010-00003
Source: Applied Health Economics and Health Policy[ISSN 1175-5652],v. 5, p. 11-25
Appears in Collections:Reseña
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