42: Practical Consideration for a Test for Proportion for Retrospective Studies in Rare Disease Settings

Music City Center 

Retrospective studies provide a viable alternative means for collecting important clinical information in situations where conducting prospective clinical trials is difficult, such as in rare disease settings. In clinical settings where the main endpoint of interest is an event-type, e.g., successful treatment of bleeding episodes or presence of treatment-related adverse events, the length of the look-up period for each patient in the study will greatly influence the number of events that each patient will contribute to the study. Use of event-type endpoints in this setting leads to analytic models that consider correlation of events within subjects. An example of a model that allows for testing a success proportion for binary events is proposed. The resulting test takes into account the correlation of events within subjects and is shown to have a limiting normal distribution. The power of the test is examined through simulations considering small sample settings, different event rates, and varying look-up times. Results show that the power of the test for proportion is sensitive to varying lengths of the patients' look-up periods.

retrospective study

rare disease

event-type endpoint

correlation

look-up period

power 

Biopharmaceutical Section