How is medical capacity determined in a patient?

From the Guidelines

Medical capacity in a patient is determined by evaluating their functional capacity, which can be estimated from their ability to perform activities of daily living, with a threshold of 4 METs (metabolic equivalents) being a common benchmark for assessing perioperative cardiac risk. This approach is supported by the American College of Cardiology/American Heart Association guidelines, as outlined in the 2009 update 1 and the 2007 guidelines 1.

Key Considerations

• Functional capacity can be classified as excellent, good, moderate, poor, or unknown, based on the patient's ability to perform activities that require different levels of energy expenditure.
• The Duke Activity Status Index or other activity scales can be used to estimate a patient's functional capacity, with questions that assess their ability to perform daily activities and leisure activities.
• Examples of activities that require less than 4 METs include slow ballroom dancing, golfing with a cart, and walking at a speed of approximately 2 to 3 mph, while activities that require more than 4 METs include moderate cycling, climbing hills, and jogging.

Assessment Tools

• The 6-minute walk test (6MWT) is a practical and simple test that can be used to assess functional capacity, as described in the 2002 ATS statement 1.
• Cardiopulmonary exercise testing may be considered for patients undergoing elevated risk procedures in whom functional capacity is unknown, as recommended in the 2014 ACC/AHA guideline 1.

Decision-Making Capacity

• In patients with cognitive impairment, decisional capacity must be evaluated prior to obtaining informed consent, taking into account their ability to understand, appreciate, reason, and make choices about their treatment, as discussed in the 2021 review on dental informed consent challenges 1.
• A multidisciplinary care team approach may be beneficial in complex cases, and simplified treatment plans and maintenance protocols may be warranted to avoid adverse effects on the patient's quality of life and health.

From the Research

Determining Medical Capacity

To determine medical capacity in a patient, several factors must be considered, including the patient's ability to understand the benefits and risks of a proposed treatment or intervention, appreciate the consequences of their decision, and reason in their thought process 2.

Assessment of Medical Decision-Making Capacity

The assessment of medical decision-making capacity should occur in the context of specific medical decisions when incapacity is considered 3. Several formal assessment tools are available to help with the capacity evaluation, including the Aid to Capacity Evaluation (ACE), the Hopkins Competency Assessment Test, and the Understanding Treatment Disclosure 3.

Evaluation Tools

• The Mini-Mental State Examination (MMSE) can be useful in assessing capacity, particularly at extreme scores 3, 4.
• The ACE is considered the best available instrument to assist physicians in making assessments of medical decision-making capacity 3.
• The Addenbrooke's Cognitive Examination (ACE-III) is a more extensive testing tool than MMSE and can show the relationship between global cognition and motor skills 4.

Challenges and Limitations

There is currently no gold standard for capacity assessment, and a lack of a uniform approach or a singular test to determine capacity 5. A multidisciplinary approach to decision-making capacity assessment could be an effective model in the hospital setting, especially in rural health due to limited access to aged care specialists 5.

Predicting Rehabilitation Outcome

Neuropsychological tests, combined with duration of rehabilitation, can predict mobility gains for patients undergoing inpatient rehabilitation beyond what is predicted by another assessment of cognition 6. Raw neuropsychological test scores may perform better than age-adjusted scores in predicting real-world function 6.

Capacity Assessment in Practice

Any physician can evaluate capacity, and a structured approach is best 2. Consultation with a psychiatrist may be helpful in some cases, but the final determination on capacity is made by the treating physician 2. If a patient is found not to have capacity, a surrogate decision maker should be identified and consulted 2.