A new approach to the analysis of clinical drug trials with withdrawals.

In clinical drug trials which require observation of patients for more than a few days or weeks, some patients may withdraw before completing the planned course of the trial for reasons that are related to the therapy, for example adverse experiences or lack of therapeutic effect. If the number of such withdrawals is material, then analysis of the data from these trials should account for these withdrawals. Ignoring them in the analyses or using the last recorded value before withdrawl can lead to misleading conclusions. If the response outcomes can be ordered so that, for instance, adverse withdrawals can be regarded as "bad" outcomes, then the withdrawals can be incorporated into the analyses straightforwardly. The method is described and illustrated, and several issues arising in its application are discussed.