Sample Size Recalculation in Internal Pilot Study Designs: A Review

Friede, Tim; Kieser, Meinhard

doi:10.1002/bimj.200510238

Cited by 172 publications

(151 citation statements)

References 54 publications

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“…Sample size reviews are used when the variance is unknown at the start of the study. 18 An SD of 17 mm Hg was observed for systolic 24-hour ABP after enrollment of 30 patients and, based on this, a 10 mm Hg difference could be detected with 46 patients at 90% power and 5% significance. Assuming a dropout rate of 10% during follow-up, as observed within the Rheos trial, the study aimed to include at least 51 patients.…”

Section: Patients Bat and Study Protocolmentioning

confidence: 99%

Effects of Baroreflex Activation Therapy on Ambulatory Blood Pressure in Patients With Resistant Hypertension

et al. 2016

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Baroreflex activation therapy (BAT) has been demonstrated to decrease office blood pressure (BP) in the randomized, double-blind Rheos trial. There are limited data on 24-hour BP changes measured by ambulatory BP measurements (ABPMs) using the first generation rheos BAT system suggesting a significant reduction but there are no information about the effect of the currently used, unilateral BAT neo device on ABPM. Patients treated with the BAT neo device for uncontrolled resistant hypertension were prospectively included into this study. ABPM was performed before BAT implantation and 6 months after initiation of BAT. A total of 51 patients were included into this study, 7 dropped out from analysis because of missing or insufficient follow-up. After 6 months, 24-hour ambulatory systolic (from 148±17 mm Hg to 140±23 mm Hg, P <0.01), diastolic (from 82±13 mm Hg to 77±15 mm Hg, P <0.01), day- and night-time systolic and diastolic BP (all P ≤0.01) significantly decreased while the number of prescribed antihypertensive classes could be reduced from 6.5±1.5 to 6.0±1.8 ( P =0.03). Heart rate and pulse pressure remained unchanged. BAT was equally effective in reducing ambulatory BP in all subgroups of patients. This is the first study demonstrating a significant BP reduction in ABPM in patients undergoing chronically stimulation of the carotid sinus using the BAT neo device. About that BAT-reduced office BP and improved relevant aspects of ABPM, BAT might be considered as a new therapeutic option to reduce cardiovascular risk in patients with resistant hypertension. Randomized controlled trials are needed to evaluate BAT effects on ABPM in patients with resistant hypertension accurately.

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Section: Patients Bat and Study Protocolmentioning

confidence: 99%

Effects of Baroreflex Activation Therapy on Ambulatory Blood Pressure in Patients With Resistant Hypertension

et al. 2016

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“…Stratification of trial results based on severity of illness at baseline (46,47). Adaptive trial designs (e.g., using biomarkers to stratify patients into more homogeneous subgroups [41], event-driven adaptive trials [36], or starting trials with several arms and then adjusting sample sizes [48] or narrowing arms based on observed interim safety and efficacy data [49]). Participant accrual and retention RCTs are sufficiently powered but patient attrition leads to appreciable postrandomization losses so that the intention-to-treat analyses are highly conservative.…”

Section: Acknowledgmentmentioning

confidence: 99%

Outcomes and Statistical Power in Adult Critical Care Randomized Trials

Harhay

Wagner²,

Ratcliffe³

et al. 2014

Am J Respir Crit Care Med

150

136

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Rationale: Intensive care unit (ICU)-based randomized clinical trials (RCTs) among adult critically ill patients commonly fail to detect treatment benefits.Objectives: Appraise the rates of success, outcomes used, statistical power, and design characteristics of published trials.Methods: One hundred forty-six ICU-based RCTs of diagnostic, therapeutic, or process/systems interventions published from January 2007 to May 2013 in 16 high-impact general or critical care journals were studied.Measurement and Main Results: Of 146 RCTs, 54 (37%) were positive (i.e., the a priori hypothesis was found to be statistically significant). The most common primary outcomes were mortality (n = 40 trials), infection-related outcomes (n = 33), and ventilationrelated outcomes (n = 30), with positive results found in 10, 58, and 43%, respectively. Statistical power was discussed in 135 RCTs (92%); 92 cited a rationale for their power parameters. Twenty trials failed to achieve at least 95% of their reported target sample size, including 11 that were stopped early due to insufficient accrual/ logistical issues. Of 34 superiority RCTs comparing mortality between treatment arms, 13 (38%) accrued a sample size large enough to find an absolute mortality reduction of 10% or less. In 22 of these trials the observed control-arm mortality rate differed from the predicted rate by at least 7.5%.Conclusions: ICU-based RCTs are commonly negative and powered to identify what appear to be unrealistic treatment effects, particularly when using mortality as the primary outcome. Additional concerns include a lack of standardized methods for assessing common outcomes, unclear justifications for statistical power calculations, insufficient patient accrual, and incorrect predictions of baseline event rates.

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“…Kieser and Friede (2000) and Denne and Jennison (2000) deal with the special problem of sample size readjustment with respect to an interim variance estimate for the t-test, when no information on interim treatment differences is used. We refer to the recent reviews of sample size re-estimation methods based on mid-course estimates of nuisance parameters by Proschan (2005) and by Friede and Kieser (2006) in the present volume. Bauer and Kieser (1999) have derived a combination test for multi-armed trials with treatment selection on the first stage and subsequent efficacy testing of the selected treatment arm incorporating the information obtained from the first stage.…”

Section: Discussionmentioning

confidence: 99%

An Overview of Statistical Approaches for Adaptive Designs and Design Modifications

2006

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With adaptive design methods for clinical trials, design elements such as sample size or further interim sample sizes may be changed during the course of the trial depending on all previously collected data. The focus of the overview is on group sequential approaches where the types of adaptations need not be specified in advance. An overview of the different statistical approaches for adaptive design methods proposed in the literature is given, relations between these methods are described and some perspectives of application and for future research are discussed.

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Sample Size Recalculation in Internal Pilot Study Designs: A Review

Cited by 172 publications

References 54 publications

Effects of Baroreflex Activation Therapy on Ambulatory Blood Pressure in Patients With Resistant Hypertension

Effects of Baroreflex Activation Therapy on Ambulatory Blood Pressure in Patients With Resistant Hypertension

Outcomes and Statistical Power in Adult Critical Care Randomized Trials

An Overview of Statistical Approaches for Adaptive Designs and Design Modifications

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