How to analyze data when there is violation of the positivity assumption? Several possible solutions exist in the literature. In this paper, we consider propensity score (PS) methods that are commonly used in observational studies to assess causal treatment effects in the context where the positivity assumption is violated. We focus on and examine four specific alternative solutions to the inverse probability weighting (IPW) trimming and truncation: matching weight (MW), Shannon\'s entropy weight (EW), overlap weight (OW), and beta weight (BW) estimators. We first specify their target population, the population of patients for whom clinical equipoise, that is, where we have sufficient PS overlap. Then, we establish the nexus among the different corresponding weights (and estimators); this allows us to highlight the shared properties and theoretical implications of these estimators. Finally, we introduce their augmented estimators that take advantage of estimating both the propensity score and outcome regression models to enhance the treatment effect estimators in terms of bias and efficiency. We also elucidate the role of the OW estimator as the flagship of all these methods that target the overlap population. Our analytic results demonstrate that OW, MW, and EW are preferable to IPW and some cases of BW when there is a moderate or extreme (stochastic or structural) violation of the positivity assumption. We then evaluate, compare, and confirm the finite-sample performance of the aforementioned estimators via Monte Carlo simulations. Finally, we illustrate these methods using two real-world data examples marked by violations of the positivity assumption.

OBJECTIVE: The embedded Qualitative Process Evaluation (QPE) within the CSTICH- Pilot RCT explored facilitators and barriers to recruitment within the Pilot. This study reports a secondary analysis of the overarching theme of Fluidity of Equipoise and the influences on individual and community clinical equipoise around the use of Emergency Cervical Cerclage (ECC).
METHODS: RCT recruitment assumes clinical equipoise and is defined as genuine uncertainty about an intervention. The ability of trial recruiters to convey this equipoise is also key to participant recruitment and fully informed consent. This exploratory qualitative process evaluation used semi-structured interviews with healthcare professionals (HCPs) involved in trial recruitment. Interviews were audio-recorded, transcribed, and analysed using codebook thematic analysis.
RESULTS: 23 HCPs were interviewed. Clinical equipoise around the use of ECC was variable and influenced by a multitude of factors including: (1) obstetric history; (2) gestation; (3) standard site practice, and (4) HCPs previous experiences of ECC. We have interpreted this variability as \'fluidity of equipoise\'.
CONCLUSIONS: Clinical equipoise around complex pregnancy related conditions was fluid and influenced by the complexities of obstetric histories and gestation at presentation. Equipoise of HCPs involved in trial recruitment should be considered carefully as it can impact the nuances of recruitment, particularly in more challenging trials such as CSTICH-2. Study-specific documents and training can be used to increase staff and patient awareness of uncertainty in the evidence base for interventions under investigation. Further research is needed around the potential consequences of equipoise fluidity.

Over recent decades, adaptive trial designs have been used more and more often for clinical trials, including randomized controlled trials (RCTs). This rise in the use of adaptive RCTs has been accompanied by debates about whether such trials offer ethical and methodological advantages over traditional, fixed RCTs. This study examined how experts on clinical trial methods and ethics believe that adaptive RCTs, compared to fixed ones, affect the ethical character of clinical research. We conducted in-depth interviews with 17 researchers from bioethics, epidemiology, biostatistics, and/or medical backgrounds. While about half believed that adaptive trials are more complex and may thus threaten autonomy, these respondents also expressed that this challenge is not insurmountable. Most respondents expressed that efficiency and potential for participant benefit were the main justifications for adaptive trials. There was tension about whether adaptive randomization in response to increasing information disrupts clinical equipoise, with some respondents insisting that uncertainty still exists and therefore clinical equipoise is not disrupted. These findings suggest that further discussion is needed to increase the awareness and utility of these study designs.

UNASSIGNED: The optimal revascularization approach in patients with heart failure with reduced ejection fraction (HFrEF) and ischemic heart disease (\"ischemic cardiomyopathy\") is unknown. Physician preferences regarding clinical equipoise for mode of revascularization and their willingness to consider offering enrollment in a randomized trial to patients with ischemic cardiomyopathy have not been characterized.
UNASSIGNED: We conducted two anonymous online surveys: 1) a clinical case scenario-based survey to assess willingness to offer clinical trial enrollment for a patient with ischemic cardiomyopathy (overall response rate to email invitation 0.45 %), and 2) a Delphi consensus-building survey to identify specific areas of clinical equipoise (overall response rate to email invitation 37 %).
UNASSIGNED: Among 304 physicians responding to the clinical case scenario-based survey, the majority were willing to offer the opportunity for clinical trial enrollment to a prototypical patient with ischemic cardiomyopathy (92 %), and felt that a finding of non-inferiority for PCI vs. CABG would influence their clinical practice (78 %). Among 53 physicians responding to the Delphi consensus-building survey, the median appropriateness rating for CABG was significantly higher than that of PCI (p < 0.0001). In 17 scenarios (11.8 %), there was no difference in CABG or PCI appropriateness ratings, suggesting clinical equipoise in these settings.
UNASSIGNED: Our findings demonstrate willingness to consider offering enrollment in a randomized clinical trial and areas of clinical equipoise, two factors that support the feasibility of a randomized trial to compare clinical outcomes after revascularization with CABG vs. PCI in selected patients with ischemic cardiomyopathy, suitable coronary anatomy and co-morbidity profile.

UNASSIGNED: Among international cardiologists it is unclear whether equipoise exists regarding the benefit of diagnosing and managing obstructive sleep apnea (OSA) to improve atrial fibrillation (AF) outcomes and whether clinical practice and equipoise are linked.
UNASSIGNED: Between January 2019 and June 2020 we distributed a web-based 12-question survey regarding OSA and AF management to practicing cardiologists in 16 countries.
UNASSIGNED: The United States, Japan, Sweden, and Turkey accounted for two-thirds of responses. 863 cardiologists responded; half were general cardiologists, a quarter electrophysiologists. Responses regarding treating OSA with CPAP to improve AF endpoints were mixed. 33% of respondents referred AF patients for OSA screening. OSA was diagnosed in 48% of referred patients and continuous positive airway pressure (CPAP) was prescribed for 59% of them. Nearly 70% of respondents believed randomized controlled trials (RCTs) of OSA treatment in AF patients were necessary and indicated willingness to contribute to such trials.
UNASSIGNED: There was no clinical equipoise among surveyed cardiologists; a majority expressed certainty that combined OSA and AF treatment is superior to AF treatment alone for improving AF outcomes. However, a minority of surveyed cardiologists referred AF patients for OSA testing, and while half of screened AF patients had OSA, CPAP was prescribed in little more than half of them, reflecting the view that better clinical trial evidence is needed to support this practice. Our results underscore the need for larger, multi-national prospective studies of OSA treatment and AF outcomes to inform more uniform society guideline recommendations.

Clinical trials are performed to determine the safety, efficacy, or effectiveness of a medical or surgical intervention. A clinical trial is, by definition, prospective in nature with a uniform treatment of a defined patient cohort. The outcomes assessment should also be uniform. Often a control group is included. At present, the number of neurosurgical clinical trials is increasing, and the study designs have become more sophisticated. Historically, the standard of neurosurgical care has evolved from the findings from many case series and retrospective comparative studies. However, in the present report, we have focused exclusively on prospective clinical trials. An urgent need exists to understand how clinical trials have been performed in the past and how they can be improved to advance our neurosurgical practice. In the present review, we have discussed the barriers, successes, and failures regarding prospective clinical trials in neurosurgery with an outlook to the future.

Between December 2020 and March 2021, the US Food and Drug Administration and the European Medicines Agency issued Emergency Use Authorizations and Conditional Marketing Authorizations for the distribution of the first COVID-19 vaccines. Although these vaccines were thoroughly assessed before their approval, regulators required companies to continue ongoing placebo-controlled clinical trials in order to gather further reliable scientific information on their safety and efficacy, as well as to start new studies to evaluate additional candidates. The aim of this paper is to present and discuss the ethical issues raised by the tension between the need to continue these types of clinical trials and the obligations related to the protection of the rights and well-being of research participants. Specifically, we question whether-how, and to what extent-fundamental principles governing research involving human beings can be applied to the current pandemic situation. We argue that continuing ongoing placebo-controlled clinical trials can be considered ethically justifiable only if all participants are adequately informed of any developments that may affect their willingness to remain enrolled, including the current situation of resource scarcity and the prioritization criteria established for vaccination. However, we also argue that currently approved vaccines, which are considered safe and effective enough to be administered to millions of people as part of the vaccination campaign, necessarily represent the \"best proven intervention\" currently available and, therefore, should be used as comparators in future studies instead of placebo.

In a prospective observational study (pre-AndroCoV Trial), the use of nitazoxanide, ivermectin and hydroxychloroquine demonstrated unexpected improvements in COVID-19 outcomes when compared to untreated patients. The apparent yet likely positive results raised ethical concerns on the employment of further full placebo controlled studies in early-stage COVID-19. The present analysis aimed to elucidate, through a comparative analysis with two control groups, whether full placebo-control randomized clinical trials (RCTs) on early-stage COVID-19 are still ethically acceptable. The Active group (AG) consisted of patients enrolled in the Pre-AndroCoV-Trial (n = 585). Control Group 1 (CG1) consisted of a retrospectively obtained group of untreated patients of the same population (n = 137), and Control Group 2 (CG2) resulted from a precise prediction of clinical outcomes based on a thorough and structured review of indexed articles and official statements. Patients were matched for sex, age, comorbidities and disease severity at baseline. Compared to CG1 and CG2, AG showed reduction of 31.5-36.5% in viral shedding (p < 0.0001), 70-85% in disease duration (p < 0.0001), and 100% in respiratory complications, hospitalization, mechanical ventilation, deaths and post-COVID manifestations (p < 0.0001 for all). For every 1000 confirmed cases for COVID-19, at least 70 hospitalizations, 50 mechanical ventilations and five deaths were prevented. Benefits from the combination of early COVID-19 detection and early pharmacological approaches were consistent and overwhelming when compared to untreated groups, which, together with the well-established safety profile of the drug combinations tested in the Pre-AndroCoV Trial, precluded our study from continuing employing full placebo in early COVID-19.

Prolonged anticoagulation therapy is recommended for patients with intermediate-risk for recurrence of venous thromboembolism (VTE). The current study aimed to identify risk factors of VTE recurrence and major bleeding in intermediate-risk patients. The COMMAND VTE Registry is a multicenter registry enrolled consecutive 3027 patients with acute symptomatic VTE among 29 centers in Japan. The current study population consisted of 1703 patients with intermediate-risk for recurrence. The primary outcome measure was recurrent VTE during the entire follow-up period, and the secondary outcome measures were recurrent VTE and major bleeding during anticoagulation therapy. In the multivariable Cox regression model for recurrent VTE incorporating the status of anticoagulation therapy as a time-updated covariate, off-anticoagulation therapy was strongly associated with an increased risk for recurrent VTE (HR 9.42, 95% CI 5.97-14.86). During anticoagulation therapy, the independent risk factor for recurrent VTE was thrombophilia (HR 3.58, 95% CI 1.56-7.50), while the independent risk factors for major bleeding were age ≥ 75 years (HR 2.04, 95% CI 1.36-3.07), men (HR 1.52, 95% CI 1.02-2.27), history of major bleeding (HR 3.48, 95% CI 1.82-6.14) and thrombocytopenia (HR 3.73, 95% CI 2.04-6.37). Among VTE patients with intermediate-risk for recurrence, discontinuation of anticoagulation therapy was a very strong independent risk factor of recurrence during the entire follow-up period. The independent risk factors of recurrent VTE and those of major bleeding during anticoagulation therapy were different: thrombophilia for recurrent VTE, and advanced age, men, history of major bleeding, and thrombocytopenia for major bleeding. CLINICAL TRIAL REGISTRATION: Unique identifier: UMIN000021132. COMMAND VTE Registry: http://www.umin.ac.jp/ctr/index.htm .

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