Low Participation Rates

2018 ◽  
pp. 62-70
Author(s):  
Dean Karlan ◽  
Jacob Appel
Keyword(s):  
Sample Size ◽  
Treatment Effect ◽  
General Public ◽  
Effective Sample Size ◽  
Random Assignment ◽  
Participation Rates ◽  
Intake Process ◽  
Positive Treatment Effect ◽  
Positive Treatment

This chapter focuses on low participation rates. Low participation rates squeeze the effective sample size for a test, making it more difficult, statistically, to identify a positive treatment effect. There are two moments in which low participation rates can materialize: during the intake process to a study or intervention, or after random assignment to treatment or control. Low participation during the intake process often occurs when marketing a program to the general public. Researchers working in the field with partner organizations often face inflexible constraints in trying to cope with low participation during intake. The second type of low participation—that which occurs after subjects have been randomly assigned to treatment or control—is a more daunting problem and is less likely solvable than low participation at the intake phase.

scholarly journals Efficacy of Zoledronic Acid in Patients with Systemic Osteoporosis and Problem of «Non Respondents» to the Treatment

2015 ◽  
Vol 22 (4) ◽  
pp. 39-43
Author(s):  
S. S Rodionova ◽  
Yu. V Buklemishev
Keyword(s):  
Bone Formation ◽  
Treatment Effect ◽  
Biochemical Tests ◽  
Zolendronic Acid ◽  
Bone Formation Markers ◽  
Study Results ◽  
Positive Treatment Effect ◽  
Positive Treatment ◽  
The Relationship ◽  
Mineral Bone Density

Prospective study of zolendronic acid efficacy was performed in 112 patients with systemic osteoporosis. Study results confirmed the presence of patients who did not response to the treatment: in 15.7 % of observations reduction of mineral bone density (BMD) continued to progress. No significant differences in initial deviations of resorption and bone formation markers, peculiarities of calcium homeostasis were detected in “non respondents”. At the same time by the 12th month after treatment initiation the relationship between BMD increase with preservation of marked decrease of resorption marker (deoxypyridinoline) and bone formation marker (osteocalcin) was noted, that pointed out the expediency of prognostic model creation. Evaluation of the influence of certain risk factors (age, results of blood and urine biochemical tests, data of densitometry including the results of femoral neck BMD in some patients) using discriminant analysis showed that 81.5% of patients were correctly referred to the groups of patients who responded and not responded to treatment. Out of all initially studied parameters the most significant were 7 that in 78.6% of cases (method sensitivity) enabled to identify the patients with negative treatment effect and in 82.1% of cases (method specificity) - with positive treatment effect.

Effects of Sodium Bicarbonate Ingestion on Anaerobic Performance: A Meta-Analytic Review

1993 ◽  
Vol 3 (1) ◽  
pp. 2-28 ◽  
Author(s):  
Larry G. Matson ◽  
Zung Vu Tran
Keyword(s):  
Sodium Bicarbonate ◽  
Treatment Effect ◽  
Anaerobic Exercise ◽  
Time To Exhaustion ◽  
Analytic Review ◽  
Positive Treatment Effect ◽  
Measured Time ◽  
Positive Treatment ◽  
Extracellular Environment ◽  
Induced Alkalosis

Many researchers have investigated the effects of induced metabolic alkalosis, by ingestion of sodium bicarbonate, on anaerobic exercise performance. But the results have been inconsistent and often contradictory. The purpose of this review was to synthesize the varied findings using a meta-analytic approach. Twenty-nine investigations met our inclusion criteria. Results show that, ingestion clearly results in a more alkaline extracellular environment. The dosage, however, was only moderately related to the increase in pH and HCO3-. Overall, performance was enhanced but the range of effect sizes was large, -0.12 to 2.87. In studies that measured time to exhaustion, there was a mean 27±20% increase in duration. The treatment effect, however, was only weakly related to the degree of induced alkalosis. But in comparing the 19 studies that showed a positive treatment effect with the 16 that showed no effect, the former were associated with a greater increase in pH following ingestion of a somewhat larger dosage, and a greater decrease in pH with exercise.

Sample size re-estimation in a superiority clinical trial using a hybrid classical and Bayesian procedure

2018 ◽  
Vol 28 (6) ◽  
pp. 1852-1878
Author(s):  
Maria M Ciarleglio ◽  
Christopher D Arendt
Keyword(s):  
Pilot Study ◽  
Sample Size ◽  
Estimation Method ◽  
Estimation Procedure ◽  
Prior Beliefs ◽  
Traditional Methods ◽  
Internal Pilot ◽  
Positive Treatment Effect ◽  
Positive Treatment ◽  
Internal Pilot Study

When designing studies involving a continuous endpoint, the hypothesized difference in means ([Formula: see text]) and the assumed variability of the endpoint ([Formula: see text]) play an important role in sample size and power calculations. Traditional methods of sample size re-estimation often update one or both of these parameters using statistics observed from an internal pilot study. However, the uncertainty in these estimates is rarely addressed. We propose a hybrid classical and Bayesian method to formally integrate prior beliefs about the study parameters and the results observed from an internal pilot study into the sample size re-estimation of a two-stage study design. The proposed method is based on a measure of power called conditional expected power (CEP), which averages the traditional power curve using the prior distributions of θ and [Formula: see text] as the averaging weight, conditional on the presence of a positive treatment effect. The proposed sample size re-estimation procedure finds the second stage per-group sample size necessary to achieve the desired level of conditional expected interim power, an updated CEP calculation that conditions on the observed first-stage results. The CEP re-estimation method retains the assumption that the parameters are not known with certainty at an interim point in the trial. Notional scenarios are evaluated to compare the behavior of the proposed method of sample size re-estimation to three traditional methods.

scholarly journals ANTIOXIDANT SUPPLEMENTS IN ALZHEIMER’S DEMENTIA AND MILD COGNITIVE IMPAIRMENT: A SYSTEMATIC REVIEW

2016 ◽  
pp. 1-8
Author(s):  
E.J. Pegg
Keyword(s):  
Oxidative Stress ◽  
Systematic Review ◽  
Cognitive Impairment ◽  
Mild Cognitive Impairment ◽  
Treatment Effect ◽  
Risk Of Bias ◽  
Positive Treatment Effect ◽  
Positive Treatment ◽  
Antioxidant Supplements ◽  
Overall Risk

Objective: Current treatments have only a modest effect on impairment in Alzheimer’s Dementia (AD) and there is no treatment currently licensed for Mild Cognitive Impairment (MCI). Oxidative stress is postulated to play a role in the pathogenesis of AD and MCI and this provides a rationale for treatment with antioxidant supplements. The aim of this review is to evaluate the effect of antioxidant supplements in people with AD and MCI. Methods: A systematic review of published randomised controlled trials was carried out. 4 electronic databases were searched. Studies were included if they compared the use of a placebo with the following antioxidant supplements in people with AD or MCI: Vitamin e, vitamin c, selenium, alpha lipoic acid, phenols, zinc, curcumin, beta carotene, coenzyme Q10, melatonin. The primary outcome measure was cognitive impairment. Secondary outcome measures included functional impairment, behavioural disturbance and safety. Results: 10 trials were identified which met the inclusion criteria. Outcome data was not suitable for meta-analysis. 5 studies reported a small positive treatment effect on cognition and 1 reported a negative effect. 2 reported a positive treatment effect on functional ability and 1 on behaviour. There were no consistent adverse effects found overall however two studies raised concern of possible worsening of cognition in certain circumstances. Conclusions: The findings of this systematic review do not support the use of antioxidant supplements to slow cognitive, functional or behavioural deterioration in people with AD or MCI. However the majority of included studies had a high or unknown risk of bias. In the one study which had a low overall risk of bias, there was evidence that antioxidant supplements may have a positive effect on functional decline in AD. The overall risk of harm associated with short term antioxidant supplementation appears to be low however caution is warranted. Further studies evaluating the role of oxidative stress in the pathogenesis of AD are suggested.

An analysis to quantify the overall survival (OS) benefit of sipuleucel-T accounting for the crossover in the control arm of the IMPACT study.

2012 ◽  
Vol 30 (5_suppl) ◽  
pp. 144-144
Author(s):  
Chadi Nabhan ◽  
Leonard G. Gomella ◽  
Todd DeVries ◽  
James Boyd Whitmore ◽  
Mark Walter Frohlich ◽  
...  
Keyword(s):  
Treatment Effect ◽  
Failure Time ◽  
Cellular Immunotherapy ◽  
Impact Study ◽  
Treatment Benefit ◽  
Positive Treatment Effect ◽  
Positive Treatment ◽  
Castrate Resistant Prostate Cancer ◽  
Castrate Resistant ◽  
The Impact

144 Background: Sipuleucel-T is an autologous cellular immunotherapy approved for the treatment of asymptomatic or minimally symptomatic metastatic castrate resistant prostate cancer (mCRPC). Our previous analyses on the effect of salvage crossover treatment with a product constructed from previously frozen cells (APC8015F) on OS in the control arms of mCRPC studies of sipuleucel-T suggested a positive treatment effect with salvage therapy (George DJ et al. JCO 2011;29:abstr 139). To quantify how treatment with APC8015F might have impacted the OS of the IMPACT study, we performed an exploratory analysis adjusting for the potential bias that salvage APC8015F might have had in estimating the OS advantage of sipuleucel-T. Methods: After objective disease progression, patients (pts) in the control arm were offered 3 infusions of APC8015F, an autologous immunotherapy made from cells cryopreserved at the time of control generation. A rank-preserving structural failure time (RPSFT) model, as previously described, was applied to adjust the sipuleucel-T treatment effect. Results: In the 512-pt IMPACT study, there was a 4.1-month median improvement in OS (25.8 vs 21.7 months) for sipuleucel-T compared to control (HR=0.78; 95% CI: 0.61, 0.98; p=0.032). 109/171 (64%) of control pts received APC8015F; other post-progression interventions were balanced. Median OS was 23.8 months for control pts receiving APC8015F and 11.6 months for control pts not receiving APC8015F. Using the RPSFT model, and assuming APC8015F was equally as effective as sipuleucel-T, the estimate of median OS for control was 18.0 months (HR=0.60, 95% CI: 0.41, 0.95), representing a 7.8-month median improvement in OS in favor of sipuleucel-T. Results from extensions of the RPFST model, where APC8015F is assumed to have less treatment effect than sipuleucel-T, will be presented. Conclusions: Adjusting for a positive effect of APC8015F in the control arm resulted in a sipuleucel-T OS treatment benefit in the IMPACT study ranging from 4.1 to 7.8 months. These results support a greater treatment effect of sipuleucel-T than reported in the IMPACT study and should be factored into future studies without APC8015F crossover.

Optimized multiple testing procedures for nested sub-populations based on a continuous biomarker

2020 ◽  
Vol 29 (10) ◽  
pp. 2945-2957 ◽  
Author(s):  
Alexandra Christine Graf ◽  
Dominic Magirr ◽  
Alex Dmitrienko ◽  
Martin Posch
Keyword(s):  
Treatment Effect ◽  
Multiple Testing ◽  
A Priori ◽  
Testing Procedures ◽  
Type 1 Error ◽  
Multiple Testing Procedures ◽  
Small Subgroup ◽  
Positive Treatment Effect ◽  
Positive Treatment ◽  
Large Benefit

An important step in the development of targeted therapies is the identification and confirmation of sub-populations where the treatment has a positive treatment effect compared to a control. These sub-populations are often based on continuous biomarkers, measured at baseline. For example, patients can be classified into biomarker low and biomarker high subgroups, which are defined via a threshold on the continuous biomarker. However, if insufficient information on the biomarker is available, the a priori choice of the threshold can be challenging and it has been proposed to consider several thresholds and to apply appropriate multiple testing procedures to test for a treatment effect in the corresponding subgroups controlling the family-wise type 1 error rate. In this manuscript we propose a framework to select optimal thresholds and corresponding optimized multiple testing procedures that maximize the expected power to identify at least one subgroup with a positive treatment effect. Optimization is performed over a prior on a family of models, modelling the relation of the biomarker with the expected outcome under treatment and under control. We find that for the considered scenarios 3 to 4 thresholds give the optimal power. If there is a prior belief on a small subgroup where the treatment has a positive effect, additional optimization of the spacing of thresholds may result in a large benefit. The procedure is illustrated with a clinical trial example in depression.

Positive Treatment Effect of Estradiol in Postpartum Psychosis

2000 ◽  
Vol 61 (3) ◽  
pp. 166-169 ◽  
Author(s):  
Antti Ahokas ◽  
Marjatta Aito ◽  
Ranan Rimón
Keyword(s):  
Treatment Effect ◽  
Postpartum Psychosis ◽  
Positive Treatment Effect ◽  
Positive Treatment

Effect of Subjective Verbal Uncertainty on Perception of Typographical Errors in a Proofreading Task

1978 ◽  
Vol 47 (1) ◽  
pp. 243-250 ◽  
Author(s):  
Morris B. Holbrook
Keyword(s):  
Treatment Effect ◽  
Significant Positive Correlation ◽  
Positive Correlation ◽  
Subjective Uncertainty ◽  
Positive Treatment Effect ◽  
Positive Treatment ◽  
Experimental Treatments

In contrast to its effect on most perceptual tasks, verbal uncertainty might be expected to facilitate the detection of typographical errors in proofreading. Experimental treatments consisted of messages differing in their levels of verbal uncertainty. In two proofreading tasks, 104 subjects searched for typographical errors systematically introduced into these passages of text. Task I showed a significant positive treatment effect of verbal uncertainty on recognition of errors and a significant positive correlation, across words, between subjective uncertainty and detection of typographical errors. The results for Task II were more equivocal and suggested the need for further research.

scholarly journals (Nano)Technology for Managing Plant Organisms with the Help of Targeted Impact Using the Signals of the Physical Nature

2015 ◽  
Vol 32 ◽  
pp. 32-35
Author(s):  
V.V. Karpachev ◽  
N.L. Voropaeva ◽  
T.G. Belonozhkina ◽  
E.V. Naumov ◽  
M.M. Vasilev ◽  
...  
Keyword(s):  
Treatment Effect ◽  
Agricultural Production ◽  
Growth And Development ◽  
Physical Nature ◽  
Control Technology ◽  
Nano Technology ◽  
Positive Treatment Effect ◽  
Positive Treatment ◽  
Growth Development ◽  
The Impact

One of the major problems of agricultural production has been to improve the sowing qualities of seeds to increase yields of various crops. In this regard, of particular interest is the control technology of vegetable organisms by "address the impact of" signals of the physical nature. Plasma treatment of seeds influences the growth and development of the amaranth. The effectiveness of treatment depends on the exposure time of the exposure. The largest positive treatment effect of the plasma on the growth, development and yield of amaranth has been observed when the exposure 60 seconds, leading to increased yields.

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