Capacity (Competence) Determination and Informed Consent

Basics

• Personal autonomy is a fundamental right; capacity determination is key to informed consent.
• Patients ≥18 years presumed to have legal and clinical capacity unless proven otherwise.
• Capacity: clinical evaluation by healthcare provider; competence: legal determination by court.
• Any treating provider can assess capacity; psychiatrists/neuropsychiatrists often consulted.
• Capacity involves clinical observation, use of assessment tools, and possibly guardian input.
• Four "C"s of capacity:
• Context: understands health status
• Choices: able to describe options
• Consequences: explains possible outcomes
• Consistency: maintains consistent choice
• Cognition necessary but not solely determinative.

Epidemiology

• About 1/3 of US adults complete advanced directives.
• Incidence of incapacity rising due to aging, chronic disease, better rehab, and safer surgery.
• Incapacity rates vary: ~3% of healthy seniors lack capacity; 68% in learning-disabled.

Etiology and Pathophysiology

• Dementia is the most common cause of incapacity outpatient.
• Capacity is dynamic; reassessment needed at each significant decision point.

Risk Factors for Incapacity

• Older age, multiple comorbidities, hospitalization
• Social factors: never married, no work history
• Patient factors: health illiteracy, information overload
• Provider factors: inexperience, insufficient time

General Prevention

• Early and periodic capacity assessment especially in:
• Electrolyte imbalance, delirium, anesthesia effects
• Mind-altering substance use

Commonly Associated Conditions

• Dementia, Parkinson disease, TBI
• Schizophrenia, depression, substance abuse
• Acute illness, metabolic derangement

Diagnosis

History

• Gather collateral info from family/frequent observers.
• Screen for communication barriers and reversible causes of incapacity.
• Consider cultural, religious, political, and historical patient factors.

Physical Exam

• Observe verbal responses, facial expressions, body language for warning signs.

Diagnostic Tests & Interpretation

• Initial screening via informal conversations and consent discussions.

Formal Capacity Assessment Tools

• MacArthur Competence Assessment Tool for Treatment (MacCAT-T): gold standard, 20-minute semistructured interview assessing understanding, reasoning, appreciation, and choice.
• Aid to Capacity Evaluation (ACE): 7 questions, predictive except in schizophrenia.
• Assessment of Capacity for Everyday Decision-Making (ACED): used in cognitively impaired seniors for ADLs.
• Capacity Assessment Tool (CAT): structured interview comparing two intervention choices.
• Cognitive screening (e.g., MMSE) supports but does not replace capacity assessment.

Special Considerations

• Language or communication impairments, translation needs
• Health literacy adjustments
• Research participation or refusal
• Pediatric/adolescent patients

Treatment

General Measures

• Determine urgency of decision; emergencies allow provider decision-making.
• Correct reversible impairments (electrolyte imbalance, language barriers).
• Simplify explanations; reframe questions.
• Engage proxy decision makers or next of kin; court guardianship rarely needed.

Issues for Referral

• Psychiatry, neuropsychiatry, medical ethics, healthcare attorneys as needed.

Ongoing Care

• Medical decision-making hierarchy if patient lacks capacity:
• Spouse (unless legally separated)
• Adult child
• Parent
• Adult sibling
• Adult with close knowledge of patient values and accessible

Follow-up Recommendations

• Reassess capacity at every significant healthcare decision point or when signs of change appear.

Clinical Pearls

• Use structured assessment including language barriers, reversible causes, and formal tools.
• Capacity is fluid; ongoing reassessment is essential.
• Succession order for decision-making should be followed to respect patient values.
• Combine formal assessment with individualized patient context for accurate capacity evaluation.

References

1. Barstow C, Shahan B, Roberts M. Evaluating medical decision-making capacity in practice. Am Fam Physician. 2018;98(1):40-46.
2. Yadav KN, Gabler NB, Cooney E, et al. Approximately one in three US adults completes any type of advanced directives for end-of-life care. Health Aff (Millwood). 2017;36(7):1244-1251.
3. Downey LVA, Zun L. Who has the ability to consent? Prim Care Companion CNS Disord. 2020;22(4):20m02619.
4. Weiss BD, Berman EA, Howe CL, et al. Medical decision-making for older adults without family. J Am Geriatr Soc. 2012;60(11):2144-2150.