This example shows a study where the disease assessment schedule changes over the course of the study. In this example, there are 3 distinct disease-assessment schedule patterns. A single anchor date variable (TDANCVAR) provides the anchor date for each pattern. The offset variable (TDSTOFF), used in conjunction with the anchor date variable, provides the start point of each pattern of assessments..
- The first disease-assessment schedule pattern starts at the reference start date (identified in the ADSL ANCH1DT variable) and repeats every 8 weeks for a total of 6 repeated assessments (i.e., week 8, week 16, week 24, week 32, week 40, week 48). Note that there is an upper and lower limit around the planned disease assessment target where the first assessment (8 weeks) could occur as early as day 53 and as late as week 9. This upper and lower limit (-3 days, +1 week) would be applied to all assessments during that pattern.
- The second disease assessment schedule starts from week 48 and repeats every 12 weeks for a total of 4 repeats (i.e., week 60, week 72, week 84, week 96), with respective upper and lower limits of -1 week and + 1 week.
- The third disease assessment schedule starts from week 96 and repeats every 24 weeks (week 120, week 144, and so on), with respective upper and lower limits of -1 week and + 1 week, for an indefinite length of time. The preceding schematic shows that, for the third pattern, assessments will occur until disease progression; this therefore leaves the pattern open-ended. However, when data is included in an analysis, the total number of repeats can be identified and the highest number of repeat assessments for any subject in that pattern must be recorded in the TDNUMRPT variable on the final pattern record.