Journal of clinical epidemiology
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Examining covariate balance is the prescribed method for determining the degree to which propensity score methods should be successful at reducing bias. This study assessed the performance of various balance measures, including a proposed balance measure based on the prognostic score (similar to a disease risk score), to determine which balance measures best correlate with bias in the treatment effect estimate. ⋯ Researchers should consider using prognostic score-based balance measures for assessing the performance of propensity score methods for reducing bias in nonexperimental studies.
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Comparative Study
Impact of immortal person-time and time scale in comparative effectiveness research for medical devices: a case for implantable cardioverter-defibrillators.
To assess the extent of immortal time bias in estimating the clinical effectiveness of implantable cardioverter-defibrillators (ICDs) and the impact of methods of handling immortal time bias. ⋯ Immortal time bias was detected in the ICD clinical effectiveness study, which might have led to substantial bias overestimating the treatment effect if handled by exclusion. When an appropriate landmark was selected, that method yielded similar hazard ratios to those obtained by the Mantel-Byar method, supporting the validity of the landmark method.
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Comparative Study
Stepped wedge designs could reduce the required sample size in cluster randomized trials.
The stepped wedge design is increasingly being used in cluster randomized trials (CRTs). However, there is not much information available about the design and analysis strategies for these kinds of trials. Approaches to sample size and power calculations have been provided, but a simple sample size formula is lacking. Therefore, our aim is to provide a sample size formula for cluster randomized stepped wedge designs. ⋯ For CRTs, the stepped wedge design is far more efficient than the parallel group and ANCOVA design in terms of sample size.
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We evaluated the inter-rater reliability (IRR) of assessing the quality of evidence (QoE) using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach. ⋯ Our findings suggest that trained individuals using the GRADE approach improves reliability in comparison to intuitive judgments about the QoE and that two individual raters can reliably assess the QoE using the GRADE system.
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Competing risks endpoints are frequently encountered in hematopoietic stem cell transplantation where patients are exposed to relapse and treatment-related mortality. Both cause-specific hazards and direct models for the cumulative incidence functions have been used for analyzing such competing risks endpoints. For both approaches, the popular models are of a proportional hazards type. ⋯ We argue that a complete understanding of the event dynamics requires that both hazards and cumulative incidence be analyzed side by side, and that this is generally the most rigorous scientific approach to analyzing competing risks data. That is, understanding the effects of covariates on cause-specific hazards and cumulative incidence functions go hand in hand. A case study illustrates our proposal.