CTCAE uses the word 'indicated' rather than 'required' when describing grades in which interventions help define severity. In most cases the meaning is interchangeable, but there are situations when a procedure would be indicated, but not performed due to extenuating circumstances. Example: A patient develops a pleural effusion, requires supplemental oxygen, and the clinical situation merits thoracic chest tube placement, but the patient declines the procedure. In this case grading is based on the medical opinion of what should be done, not what was actually done. 'Required' would mean that if an action was not taken, then the AE could not be graded.