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A randomized, double-blind, placebo-controlled, phase 3 trial.

**Objective: **Teriflunomide is an oral disease-modifying therapy approved for treatment of relapsing or relapsing–remitting multiple sclerosis. We aimed to provide further evidence for the safety and efficacy of teriflunomide in patients with relapsing multiple sclerosis.

**Year:** 2014

**Source:** The Lancet Neurology

**Link: **http://www.sciencedirect.com/science/article/pii/S1474442213703089

**Clinical Area: **Neurology

Sample Size Section in Paper/Protocol: |

“It was estimated that 370 patients randomly assigned to each treatment group would provide 94% power to detect a 25% relative risk reduction in annualized relapse rate, with the following assumptions: an annualized relapse rate of 0·74 for placebo; the number of relapses follows a Poisson distribution with an over- dispersion parameter of 1·3; a 1·5-year recruitment period with a linear recruitment rate (average exposure duration 1·75 years); and a 20% discontinuation rate.“ |

Summary of Necessary Parameter Estimates for Sample Size Calculation:

Parameter | Value |

Significance Level (2-Sided) | 0.05 |

Expected Placebo Rate | 0.74 |

Expected Rate Ratio | 0.75 |

Exposure Time | 1.75 |

Overdispersion Parameter | 1.3 |

Covariate Distribution | Binomial |

Proportion of Covariate | 0.5 |

Total Sample Size (adjusted for 20% dropout) | 592 |

Note that a binomial covariate proportion of 0.5 is equivalent to equal sample size in both groups.

**Step 1: **

Select the **“Poisson Regression”** table from the Select Test Design & Goal window.

This can be done **using the radio buttons** or alternatively, you can** use the search bar** at the end of the Select Test Design & Goal window.

**Step 2:**

Enter the parameter values for the power calculation taken from the study protocol

Remember to enter “0” in the R-squared field.

**Step 3:**

Enter 0.5 for ** “Proportion”** in the binomial side table.

Click ** “Compute”** to calculate the coefficient variances.

Then click **“Transfer”** to transfer them main table

**Step 4:**Beneath the table, select “

This gives a power of 92.2%. This is different from the stated power of 94%. However, based on the study protocol of the related TEMSO study and FDA Reviews, the power was originally calculated using a Mann-Whitney U test rather than using the Poisson Regression assumptions appropriate for the methodology used in this study. Using a sample size calculation designed for the actual statistical methodology is usually preferred. |

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