The collateral history: an overlooked core clinical skill.

Acute illness characteristically causes significant impairments in cognition and function in frail older patients. Identifying and reversing these impairments is impossible without a comprehensive collateral history. It is alarming that such an essential component of clinical assessment is so often disregarded and highlights the lack of awareness from clinicians of the importance of collateral history in the management of patients with dementia and delirium. This must be emphasised in both undergraduate and postgraduate teaching.