title: Assessment of patient capacity to consent to treatment.
abstract: OBJECTIVE
  To compare results of a specific capacity assessment administered by the treating clinician, and a Standardized Mini-Mental Status Examination (SMMSE), with the results of expert assessments of patient capacity to consent to treatment.
  
  
  METHODS
  Cross-sectional study with independent comparison to expert capacity assessments.
  
  
  METHODS
  Inpatient medical wards at an academic secondary and tertiary referral hospital.
  
  
  METHODS
  One hundred consecutive inpatients facing a decision about a major medical treatment or an invasive medical procedure. Participants either were refusing treatment, or were accepting treatment but were not clearly capable according to the treating clinician.
  
  
  RESULTS
  The treating clinician (medical resident or student) conducted a specific capacity assessment on each participant, using a decisional aid called the Aid to Capacity Evaluation. A specific capacity assessment is a semistructured evaluation of the participant's ability to understand relevant information and appreciate reasonably foreseeable consequences with regard to the specific treatment decision. Participants also received a SMMSE administered by a research nurse. Participants then had two independent expert assessments of capacity. If the two expert assessments disagreed, then an independent adjudication panel resolved the disagreement after reviewing videotapes of both expert assessments. Using the two expert assessments and the adjudication panel as the reference standard, we calculated areas under the receiver-operating characteristic curves and likelihood 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 assessment, likelihood ratios for detecting incapacity were as follows: definitely incapable, 20 (95% confidence interval [CI] 3. 6, 120); probably incapable, 6.1 (95% CI 2.6, 15); probably capable, 0.39 (95% CI 0.18, 0.81); and 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 had a likelihood ratio of 0. 68 (95% CI 0.35, 1.2), and a score of 24 to 30 had a likelihood ratio of 0.05 (95% CI 0.01, 0.26).
  
  
  CONCLUSIONS
  Specific capacity assessments by the treating clinician and SMMSE scores agree closely with results of expert assessments of capacity. Clinicians can use these practical, flexible, and evaluated measures as the initial step in the assessment of patient capacity to consent to treatment.
authors.affiliation: Department of Medicine, The Toronto Hospital, University of Toronto, Toronto, Ont., Canada.
authors.forename: E
authors.initials: E
authors.lastname: Etchells
authors.forename: P
authors.initials: P
authors.lastname: Darzins
authors.forename: M
authors.initials: M
authors.lastname: Silberfeld
authors.forename: P A
authors.initials: PA
authors.lastname: Singer
authors.forename: J
authors.initials: J
authors.lastname: McKenny
authors.forename: G
authors.initials: G
authors.lastname: Naglie
authors.forename: M
authors.initials: M
authors.lastname: Katz
authors.forename: G H
authors.initials: GH
authors.lastname: Guyatt
authors.forename: D W
authors.initials: DW
authors.lastname: Molloy
authors.forename: D
authors.initials: D
authors.lastname: Strang
mesh_terms: D000368:Aged; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D003657:Decision Making; D005260:Female; D006801:Humans; D007258:Informed Consent; D007297:Inpatients / Q000523:psychology; D016013:Likelihood Functions; D008297:Male; D016743:Mental Competency; D008609:Mental Status Schedule; D010358:Patient Participation; D012372:ROC Curve; D015203:Reproducibility of Results; D016312:Treatment Refusal