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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