180 Chapter 12: elements of Clinical trial Design II IntroDuCtIon: MethoDs for avoIDIng BIas When describing methods for avoiding bias, I can do no better than begin with the International Conference on Harmonization (ICH) guidelines: The most important design techniques for avoiding bias in clinical trials are blinding and randomization [emphasis added], and these should be normal features of most controlled clinical trials intended to be included in a marketing application. Most such trials follow a double- blind approach in which treatments are prepacked in accordance with a suitable randomization schedule and supplied to the trial center(s) labeled only with the subject number and the treatment period so that no one involved in the conduct of the trial is aware of the specific treatment allocated to any particular subject, not even as a code letter. 1 Blinding and randomization are the major tools for preventing bias in trial design, and I shall now discuss each in turn. Blinding