Abstract W P20: A Model to Calculate the Expected Treatment Effect in Acute Endovascular Stroke Trials

Stroke ◽  
2014 ◽  
Vol 45 (suppl_1) ◽  
Author(s):  
Maarten G Lansberg ◽  
Robin Lemmens ◽  
Soren Christensen ◽  
Nishant K Mishra ◽  
Gregory W Albers
Keyword(s):  
Literature Review ◽  
Sample Size ◽  
Endovascular Therapy ◽  
Treatment Effect ◽  
Small Sample Size ◽  
Small Sample ◽  
Absolute Difference ◽  
Sample Size Calculations ◽  
And Control ◽  
Larger Sample

Background: Recent trials have shown no benefit of endovascular therapy. This may, in part, be explained by inaccurate estimates of the treatment effect used in the sample size calculations of these trials. A predictive model which includes variables that modify the expected treatment effect might yield more accurate estimates, and could be valuable in the design of future acute stroke trials. Methods: We conducted a literature review to obtain estimates of parameters that are associated with good functional outcome (GFO) following recanalization. We developed a model to estimate the treatment effect in endovascular stroke trials and applied this model to two recently published endovascular stroke trials. Results: We estimated a 40% absolute difference in the proportion of GFO (mRS 0-2 at 90 days) associated with reperfusion in patients with ICA or M1 occlusions who have a substantial ischemic penumbra at baseline. To estimate the effect size in trials, this value was multiplied by: 1) the proportion of patients undergoing endovascular therapy in the active treatment arm; 2) the proportion of patients with occlusions of the ICA or MCA-M1; 3) the proportion of patients with a substantial penumbra and a DWI lesion <50mL; and 4) the absolute difference in the proportion of patients with reperfusion, defined as TICI 2B-3, between the endovascular treatment and control arms. Based on literature review we assumed a reperfusion rate of 20% in the control arms of IMS III and MR Rescue, a 50% prevalence of patients with substantial penumbra and DWI lesions<50 mL in IMS III, and a 75% prevalence in the penumbral arms of MR Rescue. Based on these model inputs, a 2.2% increase in GFO with endovascular therapy was expected in IMS III, which closely matches the observed 2.1% increase. For MR Rescue, the model predicted a 1.5% increase in GFO with endovascular therapy. Considering the small sample size, this equates to 0.5 additional patients with GFO which closely matches the observed result of 3 fewer patients with GFO. Conclusion: A simple model shows promise for estimating the treatment effect of endovascular stroke trials. It may be useful for the design of future trials and could lead to different inclusion criteria or larger sample sizes compared to the recently conducted studies.

scholarly journals Chloroquine and Hydroxychloroquine could be an Available Weapons to Treat COVID-19 Associated Pneumonia

2020 ◽  
pp. 52-60
Author(s):  
Nehad J. Ahmed
Keyword(s):  
Clinical Trials ◽  
Angiotensin Converting Enzyme ◽  
Sample Size ◽  
Small Sample Size ◽  
Small Sample ◽  
Google Scholar ◽  
Converting Enzyme ◽  
Larger Sample

Aims: This study aims to review the efficacy of chloroquine and hydroxychloroquine to treat coronavirus disease 2019 (COVID-19) associated pneumonia. Methodology: This review includes searching Google scholar for publications about the use of hydroxychloroquinein the treatment of COVID-19 using the words of (Covid-19) AND hydroxychloroquine. Results: Chloroquine and hydroxychloroquine have proven effective in treating coronavirus in China in vitro, but till now only few clinical trials are available and these trials were conducted on a small sample size of the patients. The efficacy of chloroquine and hydroxychloroquine is mainly due to its effect on angiotensin-converting enzyme II (ACE2). Conclusion: The use of chloroquine and hydroxychloroquine could be very promising but more trials are needed that include larger sample size and more data are required about the comparison between chloroquine and hydroxychloroquine with other antivirals.

scholarly journals Replication and contradiction of highly cited research papers in psychiatry: 10-year follow-up

2015 ◽  
Vol 207 (4) ◽  
pp. 357-362 ◽  
Author(s):  
Aran Tajika ◽  
Yusuke Ogawa ◽  
Nozomi Takeshima ◽  
Yu Hayasaka ◽  
Toshi A. Furukawa
Keyword(s):  
Sample Size ◽  
Small Sample Size ◽  
Total Sample ◽  
Small Sample ◽  
Research Papers ◽  
Effective Interventions ◽  
Mean Differences ◽  
Larger Sample ◽  
Highly Cited

BackgroundContradictions and initial overestimates are not unusual among highly cited studies. However, this issue has not been researched in psychiatry.AimsTo assess how highly cited studies in psychiatry are replicated by subsequent studies.MethodWe selected highly cited studies claiming effective psychiatric treatments in the years 2000 through 2002. For each of these studies we searched for subsequent studies with a better-controlled design, or with a similar design but a larger sample.ResultsAmong 83 articles recommending effective interventions, 40 had not been subject to any attempt at replication, 16 were contradicted, 11 were found to have substantially smaller effects and only 16 were replicated. The standardised mean differences of the initial studies were overestimated by 132%. Studies with a total sample size of 100 or more tended to produce replicable results.ConclusionsCaution is needed when a study with a small sample size reports a large effect.

scholarly journals HasChlamydia trachomatisprevalence in young women in England, Scotland and Wales changed? Evidence from national probability surveys

2019 ◽  
Vol 147 ◽  
Author(s):  
D. Z. Kounali ◽  
N. J Welton ◽  
K. Soldan ◽  
S. C. Woodhall ◽  
J. Kevin Dunbar ◽  
...  
Keyword(s):  
Sample Size ◽  
Small Sample Size ◽  
Credible Interval ◽  
Small Sample ◽  
Nucleic Acid Amplification ◽  
Absolute Difference ◽  
Chlamydia Screening ◽  
Before And After ◽  
Evidence Source ◽  
Size Estimates

AbstractWe evaluate the utility of the National Surveys of Attitudes and Sexual Lifestyles (Natsal) undertaken in 2000 and 2010, before and after the introduction of the National Chlamydia Screening Programme, as an evidence source for estimating the change in prevalence ofChlamydia trachomatis(CT) in England, Scotland and Wales. Both the 2000 and 2010 surveys tested urine samples for CT by Nucleic Acid Amplification Tests (NAATs). We examined the sources of uncertainty in estimates of CT prevalence change, including sample size and adjustments for test sensitivity and specificity, survey non-response and informative non-response. In 2000, the unadjusted CT prevalence was 4.22% in women aged 18–24 years; in 2010, CT prevalence was 3.92%, a non-significant absolute difference of 0.30 percentage points (95% credible interval −2.8 to 2.0). In addition to uncertainty due to small sample size, estimates were sensitive to specificity, survey non-response or informative non-response, such that plausible changes in any one of these would be enough to either reverse or double any likely change in prevalence. Alternative ways of monitoring changes in CT incidence and prevalence over time are discussed.

scholarly journals Lineage analysis of human papillomavirus type 39 in cervical samples of Iranian women

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Neda Hosseini ◽  
Zabihollah Shoja ◽  
Arash Arashkia ◽  
Amir-Hossein Khodadadi ◽  
Somayeh Jalilvand
Keyword(s):  
Sample Size ◽  
Small Sample Size ◽  
Small Sample ◽  
Long Control Region ◽  
E6 Gene ◽  
Sequence Variations ◽  
Geographical Regions ◽  
Hpv Types ◽  
Almost All ◽  
Larger Sample

Abstract Background The data with regards to the regional variants of distinct HPV types is of great value. Accordance with this, this study aimed to investigate the sequence variations of E6 gene and long control region of HPV 39 among normal, premalignant and malignant cervical samples in order to characterize the frequent HPV 39 variants circulating in Tehran, Iran. Methods In total, 70 cervical samples (45 normal, 16 premalignant, and 9 malignant samples) infected with HPV 39 were analyzed by nested-PCR and sequencing. Results Our results revealed that all samples belonged to A lineage. Almost all sequences (98.6%) were classified in A1 sublineage and only one sample (1.4%) was A2 sub lineage. Conclusions Our findings showed that lineages A, sublineage A1, is dominant in Tehran, Iran. However, the small sample size was the most important limitations of this study. Further studies with larger sample size from different geographical regions of Iran are necessary to estimate the pathogenicity risk of HPV 39 variants in this population.

scholarly journals Tools for Ergonomic Intervention: The Development and Analysis of a Cost Calculator

2020 ◽  
Vol 64 (1) ◽  
pp. 465-469
Author(s):  
Derek Stephens ◽  
Diana J. Schwerha
Keyword(s):  
Decision Making ◽  
Sample Size ◽  
Small Sample Size ◽  
Small Sample ◽  
Quality Data ◽  
Sample Sizes ◽  
System Usability ◽  
The Mean ◽  
Larger Sample ◽  
Ergonomic Intervention

The purpose of this study was to determine if safety professionals can use an ergonomic intervention costing calculator, which integrates performance and quality data into the costing matrix, to increase communication and better of decision making for the company. The sample size included 9 participants, which included four safety managers, four EHS managers, and one HR generalist. Results showed that all participants found the calculator very useful, well integrated, and it increased communication across the company. The mean System Usability Score (SUS) score was 82, which is rated as a perfectly acceptable software for use. Recommendations from this study include adding some additional features to the calculator, increasing awareness and availability of the calculator, and conducting further analysis using larger sample sizes. Limitations in this study include small sample size and limited interventions that were tested.

scholarly journals Assessing the Effects of Sample Size on Parametrizing a Taper Curve Equation and the Resultant Stem-Volume Estimates

Forests ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 848 ◽  
Author(s):  
Ninni Saarinen ◽  
Ville Kankare ◽  
Jiri Pyörälä ◽  
Tuomas Yrttimaa ◽  
Xinlian Liang ◽  
...  
Keyword(s):  
Sample Size ◽  
Laser Scanning ◽  
Small Sample Size ◽  
Point Clouds ◽  
Small Sample ◽  
Absolute Difference ◽  
Stem Volume ◽  
Local Conditions ◽  
Volume Estimates ◽  
Curve Equation

Large and comprehensive datasets, traditionally based on destructive stem analysis or other labor-intensive approaches, are commonly considered as a necessity in developing stem-volume equations. The aim here was to investigate how a decreasing number of sample trees affects parametrizing an existing taper curve equation and resultant stem-volume estimates. Furthermore, the potential of terrestrial laser scanning (TLS) in producing taper curves was examined. A TLS-based taper curve was derived for 246 Scots pines (Pinus sylvestris L.) from southern Finland to parametrize an existing taper curve equation. To assess sensitivity of the parametrization regarding sample size, the number of Scots pines included in the parametrization varied between full census and 1 Scots pine at a time. Root mean square error of stem-volume estimates remained ≤20.9% and the mean absolute difference was relatively constant (≤9.0%) between stem-volume estimates when the sample size included ≥46 Scots pines. Thus, it can be concluded that, with a rather small sample size, a taper curve equation can be re-parametrized for local conditions using point clouds from TLS to produce consistent stem-volume estimates.

scholarly journals Oversampling and replacement strategies in propensity score matching: a critical review focused on small sample size in clinical settings

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Daniele Bottigliengo ◽  
Ileana Baldi ◽  
Corrado Lanera ◽  
Giulia Lorenzoni ◽  
Jonida Bejko ◽  
...  
Keyword(s):  
Propensity Score ◽  
Sample Size ◽  
Propensity Score Matching ◽  
Treatment Effect ◽  
Mean Squared Error ◽  
Small Sample Size ◽  
Small Sample ◽  
Squared Error ◽  
Matching Procedure ◽  
Nominal Coverage

Abstract Background Propensity score matching is a statistical method that is often used to make inferences on the treatment effects in observational studies. In recent years, there has been widespread use of the technique in the cardiothoracic surgery literature to evaluate to potential benefits of new surgical therapies or procedures. However, the small sample size and the strong dependence of the treatment assignment on the baseline covariates that often characterize these studies make such an evaluation challenging from a statistical point of view. In such settings, the use of propensity score matching in combination with oversampling and replacement may provide a solution to these issues by increasing the initial sample size of the study and thus improving the statistical power that is needed to detect the effect of interest. In this study, we review the use of propensity score matching in combination with oversampling and replacement in small sample size settings. Methods We performed a series of Monte Carlo simulations to evaluate how the sample size, the proportion of treated, and the assignment mechanism affect the performances of the proposed approaches. We assessed the performances with overall balance, relative bias, root mean squared error and nominal coverage. Moreover, we illustrate the methods using a real case study from the cardiac surgery literature. Results Matching without replacement produced estimates with lower bias and better nominal coverage than matching with replacement when 1:1 matching was considered. In contrast to that, matching with replacement showed better balance, relative bias, and root mean squared error than matching without replacement for increasing levels of oversampling. The best nominal coverage was obtained by using the estimator that accounts for uncertainty in the matching procedure on sets of units obtained after matching with replacement. Conclusions The use of replacement provides the most reliable treatment effect estimates and that no more than 1 or 2 units from the control group should be matched to each treated observation. Moreover, the variance estimator that accounts for the uncertainty in the matching procedure should be used to estimate the treatment effect.

Application of Ultrasound Elastography for Assessing Intestinal Fibrosis in Inflammatory Bowel Disease: Fiction or Reality?

2020 ◽  
Vol 21 ◽  
Author(s):  
Roberto Gabbiadini ◽  
Eirini Zacharopoulou ◽  
Federica Furfaro ◽  
Vincenzo Craviotto ◽  
Alessandra Zilli ◽  
...  
Keyword(s):  
Inflammatory Bowel Disease ◽  
Sample Size ◽  
Bowel Disease ◽  
Small Sample Size ◽  
Shear Wave Elastography ◽  
Small Sample ◽  
Ultrasound Elastography ◽  
Invasive Technique ◽  
Intestinal Fibrosis ◽  
Inflammatory Bowel

Background: Intestinal fibrosis and subsequent strictures represent an important burden in inflammatory bowel disease (IBD). The detection and evaluation of the degree of fibrosis in stricturing Crohn’s disease (CD) is important to address the best therapeutic strategy (medical anti-inflammatory therapy, endoscopic dilation, surgery). Ultrasound elastography (USE) is a non-invasive technique that has been proposed in the field of IBD for evaluating intestinal stiffness as a biomarker of intestinal fibrosis. Objective: The aim of this review is to discuss the ability and current role of ultrasound elastography in the assessment of intestinal fibrosis. Results and Conclusion: Data on USE in IBD are provided by pilot and proof-of-concept studies with small sample size. The first type of USE investigated was strain elastography, while shear wave elastography has been introduced lately. Despite the heterogeneity of the methods of the studies, USE has been proven to be able to assess intestinal fibrosis in patients with stricturing CD. However, before introducing this technique in current practice, further studies with larger sample size and homogeneous parameters, testing reproducibility, and identification of validated cut-off values are needed.

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