scholarly journals Sample sizes based on three popular indices of risks

2018 ◽  
Vol 31 (3) ◽  
pp. e100011
Author(s):  
Hongyue Wang ◽  
Bokai Wang ◽  
Xin M Tu ◽  
Jinyuan Liu ◽  
Changyong Feng

Sample size justification is a very crucial part in the design of clinical trials. In this paper, the authors derive a new formula to calculate the sample size for a binary outcome given one of the three popular indices of risk difference. The sample size based on the absolute difference is the fundamental one, which can be easily used to derive sample size given the risk ratio or OR.

2021 ◽  
Author(s):  
Loukia Spineli

Abstract Background: To illustrate the advantages of using network meta-analysis (NMA) as compared to a trial or a pairwise meta-analysis to estimate the amount of missing outcome data (MOD) for a target comparison in order to adjust the required sample size for possible participant losses in a future trial.Methods: We introduced the concept of transitive risks to obtain the absolute risks of MOD for all interventions of the network. We used the network of a published systematic review on a binary outcome to apply the proposed concept and to calculate the required sample size in a future trial for a selected target comparison. For that comparison, we also calculated the required sample size using the corresponding trials separately, and after pooling these trials in a random-effects meta-analysis. Results: Ignoring MOD from the sample size calculation led to the smallest sample size. When either trial was considered, the risk of MOD ranged from 1% to 13% in the compared intervention arms, therefore, increasing the sample size from 1% to 12%. Performing a pairwise meta-analysis yielded a risk of MOD equal to 6% and 9% in the active and control arms, respectively, which inflated the sample size by 8%. Using NMA, the corresponding risks of MOD were 10% and 13%, which increased the sample size by 13%. Conclusions: Provided that the transitivity assumption holds, incorporating the absolute risks of MOD in the sample size calculation for a target comparison of the network led to better planning of a future trial.


1998 ◽  
Vol 17 (2) ◽  
pp. 63-66 ◽  
Author(s):  
DeJuran Richardson ◽  
Sue Leurgans

Methodology ◽  
2008 ◽  
Vol 4 (3) ◽  
pp. 132-138 ◽  
Author(s):  
Michael Höfler

A standardized index for effect intensity, the translocation relative to range (TRR), is discussed. TRR is defined as the difference between the expectations of an outcome under two conditions (the absolute increment) divided by the maximum possible amount for that difference. TRR measures the shift caused by a factor relative to the maximum possible magnitude of that shift. For binary outcomes, TRR simply equals the risk difference, also known as the inverse number needed to treat. TRR ranges from –1 to 1 but is – unlike a correlation coefficient – a measure for effect intensity, because it does not rely on variance parameters in a certain population as do effect size measures (e.g., correlations, Cohen’s d). However, the use of TRR is restricted on outcomes with fixed and meaningful endpoints given, for instance, for meaningful psychological questionnaires or Likert scales. The use of TRR vs. Cohen’s d is illustrated with three examples from Psychological Science 2006 (issues 5 through 8). It is argued that, whenever TRR applies, it should complement Cohen’s d to avoid the problems related to the latter. In any case, the absolute increment should complement d.


1990 ◽  
Vol 29 (03) ◽  
pp. 243-246 ◽  
Author(s):  
M. A. A. Moussa

AbstractVarious approaches are considered for adjustment of clinical trial size for patient noncompliance. Such approaches either model the effect of noncompliance through comparison of two survival distributions or two simple proportions. Models that allow for variation of noncompliance and event rates between time intervals are also considered. The approach that models the noncompliance adjustment on the basis of survival functions is conservative and hence requires larger sample size. The model to be selected for noncompliance adjustment depends upon available estimates of noncompliance and event rate patterns.


2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
B Zareini ◽  
P.B Blanche ◽  
A.H Holt ◽  
M.M Malik ◽  
D.P Rajan ◽  
...  

Abstract Background Development of type 2 diabetes (T2D) is common in patients with heart failure (HF), but knowledge of future cardiovascular events is lacking. Purpose We compared risk of heart failure hospitalization (HFH) or death versus ischemic events in real-life HF patients with new-onset T2D, prevalent T2D and no T2D. Methods Using the Danish nationwide registers, we identified all patients with HF between 1998–2016. The patients were separated in two different HF cohorts based on the status of T2D. One cohort consisted of HF patients with either prevalent or absent T2D at the time of HF diagnosis. The other cohort consisted of HF patients, who developed new-onset T2D, included at time of diagnosis. The two HF cohorts were analyzed separately. Outcomes for both cohorts were analyzed as time-to-first event as either an ischemic event (i.e. composite outcome of fatal and non-fatal myocardial infarction, stroke, and peripheral artery disease), HFH, or event-free death (not related to HFH or the ischemic event). For each cohort, we estimated the five-year absolute risk of ischemic event, HFH and event-free death, along with five-year risk ratio of HFH or event-free death versus ischemic events. Effects among subgroups were investigated by stratifying both cohorts based on age, gender and comorbidities present at inclusion. Results A total of 139,264 HF patients were included between 1998 and 2016, of which 29,078 (21%) patients had prevalent T2D at baseline. A total of 11,819 (8%) developed new-onset T2D and were included in the second cohort. The median duration of time between HF diagnosis and new-onset T2D diagnosis was: 4.1 years (IQR:1.5; 5.8). The absolute five-year risk of an ischemic event in patients with new-onset T2D, prevalent T2D and no T2D was: 17.9% (95% confidence interval (CI): 17.2; 18.6), 26.1% (95% CI: 25.6; 26.7), and 18.8% (95% CI:18.6; 19.0). Corresponding estimates for HFH were: 31.5% (95% CI: 30.6; 32.3), 33.6% (95% CI: 33.0; 34.2), and 30,7% (95% CI: 30.5; 31.0). The absolute five-year risk of event-free death among patients with new-onset T2D, prevalent T2D and no T2D was: 20.9% (95% CI: 20.2; 21.7), 18.9% (95% CI:18.4; 19.3), and 18.6% (95% CI: 18.4; 18.8) (see Figure). The five-year risk ratio of experiencing HFH or event-free death versus an ischemic event was: 2.9 (95% CI: 2.8; 3.1), 2.0 (95% CI:2.0; 2.1), and 2.6 (95% CI: 2.6; 2.7) for patients with new-onset T2D, prevalent T2D and no T2D, respectively. Similar results of absolute and relative risk were present across all subgroups. Conclusion In our population of HF patients, 8% developed new-onset diabetes. Development of T2D in patients with HF increases the risk of HFH and mortality three-fold. The increased risk of new-onset T2D is higher than the importance of prevalent T2D in patients with HF. Funding Acknowledgement Type of funding source: None


2021 ◽  
Author(s):  
Richard D. Riley ◽  
Thomas P. A. Debray ◽  
Gary S. Collins ◽  
Lucinda Archer ◽  
Joie Ensor ◽  
...  

2021 ◽  
Author(s):  
L. Howells ◽  
S. Gran ◽  
J. R. Chalmers ◽  
B. Stuart ◽  
M. Santer ◽  
...  

1994 ◽  
Vol 13 (8) ◽  
pp. 859-870 ◽  
Author(s):  
Robert P. McMahon ◽  
Michael Proschan ◽  
Nancy L. Geller ◽  
Peter H. Stone ◽  
George Sopko

2015 ◽  
Vol 9 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Tao-Ming Wang ◽  
Cheng-Chang Yang ◽  
Lih-Hsing Hsu ◽  
Eddie Cheng

A graceful labeling of a graph with q edges is a labeling of its vertices using the integers in [0, q], such that no two vertices are assigned the same label and each edge is uniquely identified by the absolute difference between the labels of its endpoints. The well known Graceful Tree Conjecture (GTC) states that all trees are graceful, and it remains open. It was proved in 1999 by Broersma and Hoede that there is an equivalent conjecture for GTC stating that all trees containing a perfect matching are strongly graceful (graceful with an extra condition). In this paper we extend the above result by showing that there exist infinitely many equivalent versions of the GTC. Moreover we verify these infinitely many equivalent conjectures of GTC for trees of diameter at most 7. Among others we are also able to identify new graceful trees and in particular generalize the ?-construction of Stanton-Zarnke (and later Koh- Rogers-Tan) for building graceful trees through two smaller given graceful trees.


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