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This comprehensive, unified text on the principles and practice of clinical trials presents a detailed account of how to conduct the trials. It describes the design, analysis, and interpretation of clinical trials in a non-technical manner and provides a general perspective on their historical development, current status, and future strategy. Features examples derived from the author's personal experience.

When the primary outcome of a clinical trial fails to reach its prespecified end point, can any clinically meaningful information still be derived from it? This review article addresses that question. A well-designed trial derives its credibility from the inclusion of a prespecified, a priori hypothesis that helps its authors avoid making potentially false positive claims on the basis of an exploratory analysis of the data. Nevertheless, an unreasonable yet widespread practice is the labeling of all randomized trials as either positive or negative on the basis of whether the P value for the primary outcome is less than 0.05. This view is overly simplistic. P values should be interpreted as a continuum wherein the smaller the P value, the greater the strength of the evidence for a real treatment effect. . . .

In a planned pooled analysis of two trials that evaluated empagliflozin in patients with heart failure, major adverse renal outcomes occurred in 2.8% of the patients who received empagliflozin and in 3.5% of those who received placebo. Results differed between the two trials.

When a clinical trial reaches its primary outcome, several issues must be considered before a clinical message is drawn. These issues are reviewed in this article. There is a natural tendency to simplify the findings of a clinical trial into a binary conclusion: “Was there a positive outcome — or not?” In order to address this question with some objectivity, attention is typically focused on whether the prespecified measure of success for the primary outcome has been met — that is, whether a P value of less than 0.05 has been achieved for the difference in treatments. In reality, a more nuanced interpretation requires a thorough examination of the totality of the evidence, including secondary end points, safety issues, and the size and quality of the . . .

Both DAPA-HF (assessing dapagliflozin) and EMPEROR-Reduced (assessing empagliflozin) trials showed that sodium-glucose co-transporter-2 (SGLT2) inhibition reduced the combined risk of cardiovascular death or hospitalisation for heart failure in patients with heart failure with reduced ejection fraction (HFrEF) with or without diabetes. However, neither trial was powered to assess effects on cardiovascular death or all-cause death or to characterise effects in clinically important subgroups. Using study-level published data from DAPA-HF and patient-level data from EMPEROR-Reduced, we aimed to estimate the effect of SGLT2 inhibition on fatal and non-fatal heart failure events and renal outcomes in all randomly assigned patients with HFrEF and in relevant subgroups from DAPA-HF and EMPEROR-Reduced trials. We did a prespecified meta-analysis of the two single large-scale trials assessing the effects of SGLT2 inhibitors on cardiovascular outcomes in patients with HFrEF with or without diabetes: DAPA-HF (assessing dapagliflozin) and EMPEROR-Reduced (assessing empagliflozin). The primary endpoint was time to all-cause death. Additionally, we assessed the effects of treatment in prespecified subgroups on the combined risk of cardiovascular death or hospitalisation for heart failure. These subgroups were based on type 2 diabetes status, age, sex, angiotensin receptor neprilysin inhibitor (ARNI) treatment, New York Heart Association (NYHA) functional class, race, history of hospitalisation for heart failure, estimated glomerular filtration rate (eGFR), body-mass index, and region (post-hoc). We used hazard ratios (HRs) derived from Cox proportional hazard models for time-to-first event endpoints and Cochran's Q test for treatment interactions; the analysis of recurrent events was based on rate ratios derived from the Lin-Wei-Yang-Ying model. Among 8474 patients combined from both trials, the estimated treatment effect was a 13% reduction in all-cause death (pooled HR 0·87, 95% CI 0·77–0·98; p=0·018) and 14% reduction in cardiovascular death (0·86, 0·76–0·98; p=0·027). SGLT2 inhibition was accompanied by a 26% relative reduction in the combined risk of cardiovascular death or first hospitalisation for heart failure (0·74, 0·68–0·82; p<0·0001), and by a 25% decrease in the composite of recurrent hospitalisations for heart failure or cardiovascular death (0·75, 0·68–0·84; p<0·0001). The risk of the composite renal endpoint was also reduced (0·62, 0·43–0·90; p=0·013). All tests for heterogeneity of effect size between trials were not significant. The pooled treatment effects showed consistent benefits for subgroups based on age, sex, diabetes, treatment with an ARNI and baseline eGFR, but suggested treatment-by-subgroup interactions for subgroups based on NYHA functional class and race. The effects of empagliflozin and dapagliflozin on hospitalisations for heart failure were consistent in the two independent trials and suggest that these agents also improve renal outcomes and reduce all-cause and cardiovascular death in patients with HFrEF. Boehringer Ingelheim.

Much biomedical research is observational. The reporting of such research is often inadequate, which hampers the assessment of its strengths and weaknesses and of a study's generalisability. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Initiative developed recommendations on what should be included in an accurate and complete report of an observational study. We defined the scope of the recommendations to cover three main study designs: cohort, case-control, and cross-sectional studies. We convened a 2-day workshop in September 2004, with methodologists, researchers, and journal editors to draft a checklist of items. This list was subsequently revised during several meetings of the coordinating group and in e-mail discussions with the larger group of STROBE contributors, taking into account empirical evidence and methodological considerations. The workshop and the subsequent iterative process of consultation and revision resulted in a checklist of 22 items (the STROBE Statement) that relate to the title, abstract, introduction, methods, results, and discussion sections of articles. 18 items are common to all three study designs and four are specific for cohort, case-control, or cross-sectional studies. A detailed Explanation and Elaboration document is published separately and is freely available on the Web sites of PLoS Medicine, Annals of Internal Medicine, and Epidemiology. We hope that the STROBE Statement will contribute to improving the quality of reporting of observational studies.

Despite widespread use, questions remain about the efficacy of oseltamivir in the treatment of influenza. We aimed to do an individual patient data meta-analysis for all clinical trials comparing oseltamivir with placebo for treatment of seasonal influenza in adults regarding symptom alleviation, complications, and safety. We included all published and unpublished Roche-sponsored randomised placebo-controlled, double-blind trials of 75 mg twice a day oseltamivir in adults. Trials of oseltamivir for treatment of naturally occurring influenza-like illness in adults reporting at least one of the study outcomes were eligible. We also searched Medline, PubMed, Embase, the Cochrane Central Register of Controlled Trials, and the ClinicalTrials.gov trials register for other relevant trials published before Jan 1, 2014 (search last updated on Nov 27, 2014). We analysed intention-to-treat infected, intention-to-treat, and safety populations. The primary outcome was time to alleviation of all symptoms analysed with accelerated failure time methods. We used risk ratios and Mantel-Haenszel methods to work out complications, admittances to hospital, and safety outcomes. We included data from nine trials including 4328 patients. In the intention-to-treat infected population, we noted a 21% shorter time to alleviation of all symptoms for oseltamivir versus placebo recipients (time ratio 0·79, 95% CI 0·74–0·85; p<0·0001). The median times to alleviation were 97·5 h for oseltamivir and 122·7 h for placebo groups (difference −25·2 h, 95% CI −36·2 to −16·0). For the intention-to-treat population, the estimated treatment effect was attenuated (time ratio 0·85) but remained highly significant (median difference −17·8 h). In the intention-to-treat infected population, we noted fewer lower respiratory tract complications requiring antibiotics more than 48 h after randomisation (risk ratio [RR] 0·56, 95% CI 0·42–0·75; p=0·0001; 4·9% oseltamivir vs 8·7% placebo, risk difference −3·8%, 95% CI −5·0 to −2·2) and also fewer admittances to hospital for any cause (RR 0·37, 95% CI 0·17–0·81; p=0·013; 0·6% oseltamivir, 1·7% placebo, risk difference −1·1%, 95% CI −1·4 to −0·3). Regarding safety, oseltamivir increased the risk of nausea (RR 1·60, 95% CI 1·29–1·99; p<0·0001; 9·9% oseltamivir vs 6·2% placebo, risk difference 3·7%, 95% CI 1·8–6·1) and vomiting (RR 2·43, 95% CI 1·83–3·23; p<0·0001; 8·0% oseltamivir vs 3·3% placebo, risk difference 4·7%, 95% CI 2·7–7·3). We recorded no effect on neurological or psychiatric disorders or serious adverse events. Our findings show that oseltamivir in adults with influenza accelerates time to clinical symptom alleviation, reduces risk of lower respiratory tract complications, and admittance to hospital, but increases the occurrence of nausea and vomiting. Multiparty Group for Advice on Science (MUGAS) foundation.

The effects of β-blocker therapy on clinical outcomes in patients with myocardial infarction and mildly reduced (40–49%) left ventricular ejection fraction (LVEF) are largely unknown. Four recently conducted randomised trials tested the efficacy of β blockers after a recent myocardial infarction in patients without reduced LVEF (LVEF ≥40%). However, none were individually powered to assess these effects in the subgroup of patients with mildly reduced LVEF. We aimed to assess the efficacy of β blockers in patients with myocardial infarction and mildly reduced LVEF during the index hospitalisation. We conducted an individual patient-level meta-analysis of patients with mildly reduced LVEF and no history or signs of heart failure from four recent clinical trials. These studies were included because they were randomised controlled trials testing long-term effects (median follow-up >1 year) of oral β-blocker therapy in patients who recently had a myocardial infarction (randomisation within 14 days) and had mildly reduced LVEF. No further studies were found in a systematic review (Jan 1, 2020 to June 26, 2025). A one-stage, fixed-effects, Cox proportional hazards regression model was used to assess the treatment effect of β blockers on the predefined primary composite endpoint of all-cause death, new myocardial infarction, or heart failure. All endpoints were independently adjudicated. This meta-analysis was registered with PROSPERO (CRD420251023480). 1885 patients with myocardial infarction and mildly reduced LVEF were included in the meta-analysis: 979 from the REBOOT trial, 422 from the BETAMI trial, 430 from the DANBLOCK trial, and 54 from the CAPITAL-RCT trial. Overall, 991 patients were assigned to β blockers and 894 to control (no β blockers). The primary composite endpoint occurred in 106 patients (32·6 events per 1000 patient-years) in the β-blocker group and 129 patients (43·0 per 1000 patient-years) in the no β-blocker group (hazard ratio 0·75 [95% CI 0·58–0·97]; p=0·031). No heterogeneity between the trials (trial-by-treatment pinteraction=0·95) or between countries of enrolment was observed (pinteraction=0·98). In patients with acute myocardial infarction with mildly reduced LVEF without history or clinical signs of heart failure, β-blocker therapy was associated with a reduction in the composite of all-cause death, new myocardial infarction, or heart failure. These results extend the known benefits of these agents in patients with myocardial infarction with reduced LVEF to the subgroup with mildly reduced LVEF. Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Danish Heart Foundation, Novo Nordisk Foundation, South-Eastern Norway Regional Health Authority, and Research Council of Norway.

Over 700 patients with drug-refractory paroxysmal atrial fibrillation were randomly assigned to cryoballoon or radiofrequency ablation. Cryoballoon ablation was noninferior to radiofrequency for the composite of recurrent atrial arrhythmia, use of antiarrhythmic drugs, or repeat ablation. According to a 2012 expert consensus statement, catheter ablation of drug-refractory paroxysmal atrial fibrillation is a class I level A indication, 1 and pulmonary-vein isolation is the standard approach. 1 – 3 The two most frequently used ablation technologies for pulmonary-vein isolation differ in the energy source and mode of application. The most common method is the use of radiofrequency current applied in a point-by-point mode, which leads to cellular necrosis by tissue heating; the other method is the use of cryogenic energy applied with a balloon in a single-step mode, which leads to necrosis by freezing (Figure 1). Radiofrequency ablation for atrial . . .

Much medical research is observational. The reporting of observational studies is often of insufficient quality. Poor reporting hampers the assessment of the strengths and weaknesses of a study and the generalisability of its results. Taking into account empirical evidence and theoretical considerations, a group of methodologists, researchers, and editors developed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) recommendations to improve the quality of reporting of observational studies. The STROBE Statement consists of a checklist of 22 items, which relate to the title, abstract, introduction, methods, results and discussion sections of articles. Eighteen items are common to cohort studies, case-control studies and cross-sectional studies and four are specific to each of the three study designs. The STROBE Statement provides guidance to authors about how to improve the reporting of observational studies and facilitates critical appraisal and interpretation of studies by reviewers, journal editors and readers. This explanatory and elaboration document is intended to enhance the use, understanding, and dissemination of the STROBE Statement. The meaning and rationale for each checklist item are presented. For each item, one or several published examples and, where possible, references to relevant empirical studies and methodological literature are provided. Examples of useful flow diagrams are also included. The STROBE Statement, this document, and the associated Web site (http://www.strobe-statement.org/) should be helpful resources to improve reporting of observational research.