Assessment of capacity to give informed consent

Principles

Capacity to give informed consent is decision-specific and time-specific - a patient may have capacity for a simple decision but not a complex one, and capacity can fluctuate (e.g. with delirium) even within the same day
Impaired capacity is common in the geriatric population (dementia, delirium, acute illness) but must never be assumed from a diagnosis alone - capacity is always assessed against the specific decision at hand

The standard test asks whether the patient can: understand the relevant information, retain it long enough to make the decision, weigh/use it to reach a decision, and communicate that decision (by any means) - all four elements must be intact for capacity to be present for that decision

Capacity is assessed for the specific decision being made, not globally - a patient may lack capacity to manage complex finances but retain capacity to decide about a straightforward medical treatment, or vice versa
A diagnosis of dementia or a low cognitive screening score does NOT itself equal incapacity - many patients with mild-moderate dementia retain capacity for many decisions, and capacity must be assessed directly against the decision at hand, not inferred from a diagnosis or test score

If capacity is lacking for a specific decision, identify the correct substitute decision-maker for that domain (see proxy decision makers) and proceed via substituted judgement/best interests as appropriate
Reversible causes of apparent incapacity (delirium, depression, undertreated pain, sensory impairment/communication barriers) should be actively excluded or treated before concluding a patient permanently lacks capacity

Delirium (a common reversible cause of apparent incapacity), dementia, guardianship and substitute decision-making, informed consent

Capacity assessment should be revisited whenever the clinical situation changes (e.g. delirium resolving) - a capacity assessment is a snapshot for a specific decision at a specific time, not a permanent determination

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