Assessing disease progression using a composite endpoint

Scleroderma patients usually have serious medical events in several organ systems and it is desirable to have a composite index that accounts for disease activity in these organ systems. We show how one may use a composite 'time to event' analysis for evaluating such patients and more generally for patients suffering from a chronic disease. The composite 'time to event' analysis requires a composite endpoint with a Kaplan-Meier type analysis. As an illustration, we use data from a clinical trial for scleroderma patients and present sensitivity analysis where one or more of the organ involvement definition criteria are modified. In addition, we propose desirability functions to monitor patients' disease improvement when the outcomes are all continuous. This method offers several possible advantages over existing methods for measuring patients' improvement.