Capacity Assessment

Background

Capacity refers to a patient’s ability to understand, appreciate, and make informed decisions about their medical care. It is decision-specific and time-specific, meaning a patient may have capacity for one decision but not another, or may regain capacity later. Unlike competence, which is a legal determination, capacity is a clinical judgment made by healthcare professionals.

Clinical Features

Features indicating possible impaired capacity include:

Confusion, disorientation

Delusions or hallucinations

Expressing choices inconsistent with known values

Inability to explain the nature or consequences of decisions

Fluctuating mental status or consciousness

Differential Diagnosis

Delirium (often reversible and acute)

Dementia (usually progressive and chronic)

Psychiatric illness (e.g., psychosis, depression)

Intellectual disability

Aphasia or language barriers

Influence of medications, intoxication, or metabolic derangements

Evaluation

Workup

Clinical interview focused on the four key elements of capacity:

1. Understanding: Can the patient explain the condition and options?
2. Appreciation: Does the patient recognize how the information applies to their situation?
3. Reasoning: Can the patient compare risks/benefits and explain their choice?
4. Communication: Can the patient clearly express a stable choice?

Assess for reversible causes (e.g., hypoxia, infection, intoxication)

Use structured tools if needed: MacCAT-T (MacArthur Competence Assessment Tool for Treatment), Aid to Capacity Evaluation (ACE)

Consult psychiatry if unclear or complex

Diagnosis

Capacity is not all-or-none and should be judged relative to the complexity and risk of the decision. A patient with mild cognitive impairment may still have capacity for low-risk decisions. Document reasoning and patient responses thoroughly.

Management

If the patient lacks capacity:

• Identify appropriate surrogate decision-maker (per legal hierarchy)
• Consider temporary holds or guardianship if no surrogate is available
• Treat reversible impairments and reassess
• Ensure decisions are patient-centered, honoring prior expressed wishes or advance directives
• Involve ethics consultation if disputes arise

Disposition

If capacity is regained, defer major decisions until reassessment

If patient lacks capacity and is at risk, consider admission or legal measures for protection

Ensure continuity of care planning with healthcare proxy or legal guardian

See Also

Informed Consent

Delirium

Guardianship

External Links

Aid to Capacity Evaluation (ACE)

American Bar Association: Capacity Assessment Guidelines