Repeating Instruments

Repeating instruments are used when the number of times a form must be completed is not known in advance. This is common in clinical research. A participant may have no adverse events, one adverse event, or several. A participant may take multiple concomitant medications. A participant may have several unscheduled hospital visits or multiple laboratory specimens. Creating fixed variables for every possible occurrence would make the database large, awkward, and still incomplete if more events occur than expected.