In the diagrams below, the red line represents a graph of severity over time for a hypothetical event. For most adverse events, severity cannot be measured on a continuous scale; this line represents hypothetical actual severity, not data that could be recorded. The horizontal lines divide severity into the three categories, "Mild", "Moderate", and "Severe", which are used to describe adverse event severity.
The SDTM standard event qualifier variable --SEV, Severity/Intensity, can represent only one severity value, even if, as in this hypothetical example, the severity of an event changed over time. A sponsor may decide not to capture data about changes in severity for an event. In this case, sponsors typically populate AESEV or CESEV with the maximum severity over the course of the event, as this represents the worst case.
In the example below, the double-headed arrow represents data collection in which the maximum severity over the entire course of the event was recorded. The arrow extends from the start of the event, --STDTC, marked by the first vertical blue line, to the end of the event, --ENDTC, marked by the second vertical blue line. The text in the arrow shows that --SEV was recorded as "Severe".