I would recommend using the same term when identifying involvement in clinical research trials. Generally, the trend is to use "participant" over "subject" in human clinical trials. There may be other cases not included in the two examples below.

Verbatim Example #1:
"An event (i.e. any change to current patient status) that may be related to unintended effects on a patient or research subject."

{+}Verbatim Example #2:
{+}"This resource applies to events that occur during the course of medical care or medical research which may impact an individual as the recipient of care or the participant in a research study. "