What is the difference between capacity and competence in a patient's ability to make informed decisions about their care?

Capacity vs Competence: Key Distinctions

Capacity is a clinical determination made by physicians at the bedside to assess a patient's ability to make a specific medical decision, while competence is a legal determination made by courts to assess a person's global ability to manage their affairs. 1

Core Distinction

Capacity is decision-specific and assessed by clinicians, whereas competence historically referred to global, all-or-none legal determinations. 1 The modern approach has shifted away from sweeping judgments about "competence" that resulted in global determinations of inability to manage one's affairs. 1

Practical Differences:

• Who determines it: Capacity is determined by treating clinicians in most circumstances and only rarely by lawyers or judges, yet these clinical determinations carry profound legal consequences. 1

• Scope of assessment: Capacity assessments are decision-specific—a patient may lack capacity for complex financial investments while retaining capacity for simpler decisions like grocery shopping. 1 This contrasts with older "competence" determinations that were global and all-encompassing. 1

• Terminology in practice: The terms "capacity" and "competence" are sometimes used interchangeably in informed consent discussions, but capacity is the preferred clinical term. 1

The Four-Abilities Framework for Capacity Assessment

When assessing capacity clinically, you must evaluate four specific abilities: 1, 2

1. Understanding: The patient's ability to comprehend basic relevant information including their condition, the proposed intervention, alternatives, and their risks and benefits (including no treatment). 1

2. Appreciation: The patient's acknowledgment of their medical condition and the probable consequences of treatment options—going beyond mere understanding to personal application. 1

3. Reasoning: The patient's ability to weigh risks and benefits and reach a decision consistent with that assessment through logical thought processes. 1

4. Expression of choice: The patient's ability to express a decision indicating a preferred treatment option clearly and consistently. 1

Critical Clinical Principles

Adults are presumed to have capacity unless proven otherwise through specific assessment. 1, 3 You cannot make assumptions about capacity based on age, appearance, behavior, diagnosis, or the fact that a patient makes an unwise decision. 1, 3, 2

A patient does not have to make a sensible, rational, or well-considered decision to have capacity. 1 However, a highly irrational decision based on persistent misinterpretation of information may indicate lack of capacity. 1

Common Pitfalls to Avoid

• Never make global determinations of incapacity—always specify which decisions the patient cannot make. 3, 2

• Do not rely solely on cognitive screening tools like the Mini-Mental State Examination (MMSE), as these do not assess functional decision-making abilities. 2

• Avoid vague documentation like "patient confused" without specific examples of how confusion impairs the four core abilities. 3

• Do not assume incapacity based on diagnosis alone—cognitive impairment exists on a spectrum, and many patients retain capacity for certain decisions. 1

Documentation Requirements

When documenting capacity determinations, include: 3

• Specific examples of the patient's impairment or disturbance affecting decision-making
• Evidence of assessment of all four core abilities (understanding, appreciation, reasoning, choice)
• Clinical reasoning that led to your determination
• For incapacity: identification of authorized surrogate decision-maker and review of advance directives
• Plans for reassessment when capacity may improve (especially in temporary confusion)

When Capacity Is Lacking

If you determine a patient lacks capacity for a specific decision: 3, 2

1. Identify the authorized surrogate according to state law (typically: spouse, adult child, parent, sibling, friend in that order). 1

2. Apply substituted judgment when possible—the surrogate makes the decision the patient would have made based on known values and preferences. 2

3. Use best interests standard when the patient's wishes cannot be determined—decisions should reflect what is objectively best for the patient. 1, 2

Capacity is time- and context-specific and can fluctuate, especially in delirium, dementia, or acute illness—reassess when the patient's condition changes or when making different decisions. 2