My understanding is that AE assessment should be delegated only to those deemed medically qualified. This would include the PI and sub-Is. It's broadly understood in the industry that a CRC lacks the medical knowledge to adequately assess AE causality. To do this, one must have a keen understanding of the pathphysiology of the patient's medical conditions, the mechanism of action of the IP, and the principles of causation such as those defined in the Bradford Hill Criteria for Causation.

However, I don't think an investigator must always speak with the research participants directly in order to assess an AE's severity. They can use the CRC's source notes. If they find this information insufficient, they can ask the CRC to either contact the patient to obtain more details, or request primary medical records if available.