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Table 2 Proportion of trials showing significant improvement for “stopping of recruitment” cases

From: Evaluation by simulation of clinical trial designs for evaluation of treatment during a viral haemorrhagic fever outbreak

Stopping of recruitment

Design

 

pC = 0.50

pC = 0.75

∆ = 0.20

∆ = 0

∆ = − 0.10

∆ = 0.20

∆ = 0

∆ = − 0.10

NSTOP = 20

F1

 

0.416

0.021

0.002

1

0.618

0.244

S1

(a)

0.414 (0.75)

0.021 (0.587)

0.002 (0.245)

1 (0.003)

0.615 (0.585)

0.242 (0.830)

(b)

0.234 + 0.180

0.006 + 0.015

0.0004 + 0.0012

0.997 + 0.002

0.411 + 0.204

0.116 + 0.126

F2

 

0.054

0.006

0.002

0.048

0.005

0.001

S2

(a)

0.118 (1)

0.042 (1)

0.060 (1)

0.054 (1)

0.019 (1)

0.044 (1)

(b)

0 + 0.118

0 + 0.042

0 + 0.060

0 + 0.054

0 + 0.019

0 + 0.044

NSTOP = 50

F1

 

0.858

0.032

0.0005

1

0.972

0.619

S1

(a)

0.793 (0.136)

0.023 (0.020)

0.0004 (0.0002)

1 (0)

0.948 (0.054)

0.526 (0.181)

(b)

0.720 + 0.073

0.016 + 0.007

0.0003 + 0.0001

1 + 0

0.916 + 0.032

0.438 + 0.088

F2

 

0.333

0.032

0.005

0.320

0.021

0.003

S2

(a)

0.234 (0.987)

0.016 (0.950)

0.003 (0.837)

0.420 (0.998)

0.020 (0.989)

0.017 (0.903)

(b)

0.013 + 0.221

0.0001 + 0.016

0 + 0.003

0.002 + 0.418

0 + 0.020

0 + 0;017

NSTOP = 100

F1

 

0.988

0.028

0

1

1

0.875

S1

 

0.894 (0)

0.025 (0)

0.0005 (0)

1 (0)

0.981 (0)

0.661 (0)

F2

 

0.542

0.029

0.002

0.834

0.024

0.0008

S2

(a)

0.425 (0.732)

0.012 (0.529)

0.0004 (0.190)

0.747 (0.765)

0.012 (0.766)

0.0004 (0.287)

(b)

0.255 + 0.170

0.005 + 0.007

0.0001 + 0.0003

0.236 + 0.511

0.001 + 0.011

0 + 0.0004

  1. In bold, type-I-errors maintained in [0.024;0.026]
  2. Abbreviations: pC indicates control survival rate; ∆: simulated survival rate difference; F1: fixed single-arm design; S1: group-sequential single-arm design; F2: fixed two-arm design; S2: group-sequential two-arm design; Stopping of recruitment: specific case with a fixed control survival rate and an early stop of the trial due to an outbreak end; For group-sequential trials, the total of trials demonstrating an efficacy of the experimental treatment was defined by the sum of trials with a significant test and trials with an adjusted p-value inferior to 0.025. The p-value was adjusted for underrunning using the method proposed by Whitehead [18]
  3. (a): Proportion of significant tests with proportion of inconclusive group-sequential trials for “changing with time” cases
  4. (b): Proportion of significant tests + proportion of trials with adjusted p-values inferior to 0.025 for group-sequential trials and “stopping of recruitment” cases