Table 4 Definitions of causality

None

There is no evidence of any causal relationship. N.B. an alternative cause for the AE should be given

Unlikely

There is little evidence to suggest there is a causal relationship (e.g., the event did not occur within a reasonable time after the trial procedure). There is another reasonable explanation for the event (e.g., the participant’s clinical condition, other concomitant treatment)

Possibly

There is some evidence to suggest a causal relationship (e.g., because the event occurs within a reasonable time after the trial procedure). However, the influence of other factors may have contributed to the event (e.g., chemotherapy or other concomitant treatments)

Probably

There is evidence to suggest a causal relationship and the influence of other factors is unlikely

Highly probable

There is clear evidence to suggest a causal relationship and other possible contributing factors can be ruled out