Interpretation of statistical methodology associated with maintenance trials.

Maintenance trials in ulcer disease provide a scientific framework through which the prophylactic performances of two or more therapies can be compared with respect to ulcer recurrence. For this purpose, a primary source of data is the endoscopic classification of patients at protocol-scheduled visits as well as at unscheduled visits. Several statistical issues are relevant to the analysis of this endoscopic information. First, the extent to which the respective patients have different data patterns for their ulcer recurrence status must be taken into account by actuarial methods that adjust for the length of follow-up time. Second, the role of multiple investigators requires careful attention when information is combined from them. A third issue is concerned with the assessment of the variation of ulcer recurrence experience across subgroups with respect to patient demographics, medical history, and baseline characteristics. Statistical methods can effectively address these issues so that the results of maintenance studies can be interpreted through estimates for ulcer recurrence rates. In this way, they can meaningfully support clinical conclusions about the performance of alternative therapies for maintaining the absence of ulcer disease over time.