Survivor Treatment Selection Bias and Outcomes Research
- 1 September 2009
- journal article
- research article
- Published by Ovid Technologies (Wolters Kluwer Health) in Circulation: Cardiovascular Quality and Outcomes
- Vol. 2 (5), 469-474
- https://doi.org/10.1161/circoutcomes.109.857938
Abstract
Background— Recent studies in infective endocarditis have suggested an association between surgery and reduced mortality. However, these studies did not account for survivor treatment selection bias, which is an underrecognized source of error in observational studies. Therefore, we sought to evaluate the effects of survivor bias on surgical outcomes in infective endocarditis. Methods and Results— We studied 223 patients admitted with left-sided infective endocarditis between 1996 and 2006 and compared all-cause mortality between surgically treated and medically treated patients using Cox regression analysis. Propensity scores were used to account for selection bias, and time-dependent analyses were performed to account for survivor bias. Compared with medical patients (n=161), surgical patients (n=62) had lower mortality during a median follow-up of 5.2 years (32% versus 51%; P =0.02) with an unadjusted hazard ratio of 0.54 (95% CI, 0.33 to 0.88, P =0.01). After adjustment for baseline differences in propensity for surgery and risk of mortality, there remained a significant benefit for surgery (hazard ratio, 0.50; 95% CI, 0.28 to 0.88; P =0.02). However, this was diminished after time-dependent analysis (hazard ratio, 0.77; 95% CI, 0.42 to 1.40; P =0.39). Conditional Kaplan–Meier analyses confirmed the effect of survivor bias because the apparent benefit of surgery was primarily attributable to excess mortality in the medical group during early hospitalization when surgery was not frequently performed. Conclusions— Survivor bias significantly affects the evaluation of surgical outcomes in infective endocarditis, and it should be considered in other areas of outcomes research where randomized controlled trials are not feasible. Survivor bias is not corrected by propensity analysis alone but may be reduced by time-dependent survival analysis.Keywords
This publication has 20 references indexed in Scilit:
- Rationale, design, and methods for the early surgery in infective endocarditis study (ENDOVAL 1): A multicenter, prospective, randomized trial comparing the state-of-the-art therapeutic strategy versus early surgery strategy in infective endocarditisAmerican Heart Journal, 2008
- The Impact of Valve Surgery on 6-Month Mortality in Left-Sided Infective EndocarditisCirculation, 2007
- Early Surgery in Patients with Infective Endocarditis: A Propensity Score AnalysisClinical Infectious Diseases, 2007
- Surgical treatment of active infective endocarditis: A continued challengeThe Journal of Thoracic and Cardiovascular Surgery, 2006
- Use of surgery in patients with native valve infective endocarditis: Results from the International Collaboration on Endocarditis Merged DatabaseAmerican Heart Journal, 2005
- The use and effect of surgical therapy for prosthetic valve infective endocarditis: A propensity analysis of a multicenter, international cohortAmerican Heart Journal, 2005
- Fibroblasts Can Be Genetically Modified to Produce Excitable Cells Capable of Electrical CouplingCirculation, 2005
- Proposed Modifications to the Duke Criteria for the Diagnosis of Infective EndocarditisClinical Infectious Diseases, 2000
- TIME-DEPENDENT COVARIATES IN THE COX PROPORTIONAL-HAZARDS REGRESSION MODELAnnual Review of Public Health, 1999
- A new method of classifying prognostic comorbidity in longitudinal studies: Development and validationJournal of Chronic Diseases, 1987