Assessment of patient capacity to consent to treatment

OBJECTIVE: To compare results of a specific capacity assessment administere d by the treating clinician, and a Standardized Mini-Mental Status Examinat ion (SMMSE), with the results of expert assessments of patient capacity to consent to treatment. DESIGN: Cross-sectional study with independent comparison to expert capacit y assessments. SETTING:Inpatient medical wards at an academic secondary and tertiary refer ral hospital. PARTICIPANTS: One hundred consecutive inpatients facing a decision about a major medical treatment or an invasive medical procedure. Participants eith er were refusing treatment, or were accepting treatment but were not clearl y capable according to the treating clinician. MEASUREMENTS AND MAIN RESULTS: The treating clinician (medical resident or student) conducted a specific capacity assessment on each participant, usin g a decisional aid called the Aid to Capacity Evaluation. A specific capaci ty assessment Is a semistructured evaluation of the participant's :ability to understand relevant information and appreciate reasonably foreseeable co nsequences with regard to the specific treatment decision. Participants als o received a SMMSE administered by a research nurse. Participants then had two independent expert assessments of capacity. If the two expert assessmen ts disagreed, then an independent adjudication panel resolved the disagreem ent after reviewing videotapes of both expert assessments. Using the two ex pert assessments and the adjudication panel as the reference standard, we c alculated areas under the receiver-operating characteristic curves and Like lihood ratios. The areas under the receiver-operating characteristic curves were 0.90 for specific capacity assessment by treating clinician and 0.93 for SMMSE score (2p =.48). For the treating clinician's specific capacity a ssessment, Likelihood ratios for detecting incapacity were as follows: defi nitely incapable, 20 (95% confidence interval [CI] 3.6, 120): probably inca pable, 6.1 (95% CI 2.6, 15); probably capable, 0.39 (95% CI 0.18, 0.81); an d definitely capable, 0.05 (95% CI 0.01, 0.29). For the SMMSE, a score of 0 to 16 had a likelihood ratio of 15 (95% CI 5.3, 44), a score of 17 to 23 h ad a likelihood ratio of 0.68 (95% CI 0.35, 1.2), and a score of 24 to 30 h ad a likelihood ratio of 0.05 (95% CI 0.01, 0.26). CONCLUSIONS: Specific capacity assessments by the treating clinician and SM MSE scores agree closely with results of expert assessments of capacity. Cl inicians can use these practical, flexible, and evaluated measures as the i nitial step in the assessment of patient capacity to consent to treatment.