Bias estimation in study design: a meta-epidemiological analysis of transcatheter versus surgical aortic valve replacement

Background: Paucity of RCTs of non-drug technologies lead to widespread dependence on non-randomized studies. Relationship between nonrandomized study design attributes and biased estimates of treatment effects are poorly understood. Our purpose was to estimate the bias associated with specific nonrandomized study attributes among studies comparing transcatheter aortic valve implantation with surgical aortic valve replacement for the treatment of severe aortic stenosis. Results: We included 6 RCTs and 87 nonrandomized studies. Surgical risk scores were similar for comparison groups in RCTs, but were higher for patients having transcatheter aortic valve implantation in nonrandomized studies. Nonrandomized studies underestimated the benefit of transcatheter aortic valve implantation compared with RCTs. For example, nonrandomized studies without adjustment estimated a higher risk of postoperative mortality for transcatheter aortic valve implantation compared with surgical aortic valve replacement (OR 1.43 [95% CI 1.26 to 1.62]) than high quality RCTs (OR 0.78 [95% CI 0.54 to 1.11). Nonrandomized studies using propensity score matching (OR 1.13 [95% CI 0.85 to 1.52]) and regression modelling (OR 0.68 [95% CI 0.57 to 0.81]) to adjust results estimated treatment effects closer to high quality RCTs. Nonrandomized studies describing losses to follow-up estimated treatment effects that were significantly closer to high quality RCT than nonrandomized studies that did not. Conclusion: Studies with different attributes produce different estimates of treatment effects. Study design attributes related to the completeness of follow-up may explain biased treatment estimates in nonrandomized studies, as in the case of aortic valve replacement where high-risk patients were preferentially selected for the newer (transcatheter) procedure

Empirical Estimation of Bias in Randomized and Nonrandomized Study Designs: A Meta-Epidemiological Case Study using TAVI vs. SAVR

Objective: To quantify the bias associated with nonrandomized study (NRS) design attributes in literature comparing Transcatheter Aortic Valve Implantation (TAVI) vs. Surgical Aortic Valve Replacement (SAVR). Methods: 1) Conducted meta-analysis; 2) Compared estimates of treatment effects (ETE) between study designs; 3) Identified associations between 41 NRS attributes and pooled ETE. Results: We included 87 NRSs and 6 randomized controlled trials (RCTs). Lower quality studies underestimated the benefit for TAVI. Randomization in low quality RCTs and risk adjustments in NRSs did not always bring estimates closer to high quality RCT compared to NRSs without adjustment. NRSs that described lost to follow-up reported ETE significantly closer to high quality RCTs than NRSs that did not. Conclusion: ETEs in NRSs are often biased compared to RCTs. Simply categorizing a study as an RCT or NRS fails to reflect the range of bias in each category. Factors related to follow-up may explain important bias.M.Sc

Performance of Optic Disc Drusen Diagnostic Modalities Stratified by Age and Drusen Characteristics

Enhanced Depth Imaging Optical Coherence Tomography (EDI-OCT) is emerging as the most reliable Optic Disc Drusen (ODD) diagnostic modality. However, it is unclear whether its diagnostic performance varies according to patient's age or ODD characteristics. Hence, we sought to compare the diagnostic accuracy of 4 imaging modalities-B-scan ultrasonography (US), fundus photography, fundus autofluorescence (FAF), and EDI-OCT- stratified by 1. Patient's age, 2. size and 3. depth of ODD

Atypical Presentations of Giant Cell Arteritis: The Toll of Delayed Diagnosis

Giant Cell Arteritis (GCA) is a systemic vasculitis that targets medium to large vessels. Protean manifestations of GCA can make for a diagnostic challenge and can delay life-altering treatment. We present 3 cases of atypical presentation of GCA encountered in a tertiary neuro-ophthalmology center that led to delayed diagnosis and permanent vision loss

Advanced Depreciation Cost Analysis for a Commercial Pyroprocess Facility in Korea

AbstractThe purpose of this study is to present a rational depreciation method for a pyroprocess cost calculation. Toward this end, the so-called advanced decelerated depreciation method (ADDM) was developed that complements the limitations of the existing depreciation methods such as the straight-line method and fixed percentage of declining-balance method. ADDM was used to show the trend of the direct material cost and direct labor cost compared to the straight-line or fixed percentage of the declining-balance methods that are often used today. As a result, it was demonstrated that the depreciation cost of the ADDM, which assumed a pyroprocess facility's life period to be 40 years with a deceleration rate of 5%, takes up 4.14% and 27.74% of the pyroprocess unit cost ($781/kg heavy metal) in the 1st and final years, respectively. In other words, it was found that the ADDM can cost the pyroprocess facility's capital investment rationally every year. Finally, ADDM's validity was verified by confirming that the sum of the depreciation cost by year, and the sum of the purchasing cost of the building and equipment, are the same

Topography of the Lacrimal Gland for Treating Epiphora Using Botulinum Toxin Injection

Botulinum toxin A (BTX-A) injection into the lacrimal gland has also been considered effective for relieving gustatory tearing. The purpose of this study was to identify the location of the orbital part of the lacrimal gland using external landmarks to facilitate effective and safer botulinum toxin A (BTX-A) injections for epiphora treatment