Capacity to Consent to Treatment Instrument (CCTI)

The Capacity to Consent to Treatment Instrument (CCTI) is a standardized psychometric instrument designed to assess the treatment consent capacity (TCC) of adults. The CCTI evaluates five different consent abilities or standards and has been shown to be a reliable and valid measure of TCC. The measure discriminates well between cognitively intact adults and persons with Alzheimer’s disease (AD), Parkinson’s disease dementia syndrome, and traumatic brain injury. The CCTI has application to all adult patient populations in which issues of neurocognitive impairment and consent capacity arise. Research using the CCTI has provided insight into the relationships between cognitive change and different thresholds of decisional capacity.

Structure and Administration of the CCTI

The CCTI was first developed in 1992 to empirically investigate patterns of consent capacity impairment in patients with mild and moderate AD. The measure consists of two clinical vignettes that present hypothetical medical problems and their symptoms (brain tumor, atherosclerotic heart disease) as well as treatment alternatives with the associated risks and benefits. The CCTI is administered in a way that simulates an informed consent dialogue between the physician and the patient. The vignettes are presented simultaneously in oral and written format using an uninterrupted disclosure method. They are written at a fifth- to sixth-grade reading level, with low syntactic complexity and a moderate information load.

After each vignette is presented, the written stimulus is removed, and patients are asked to answer a series of questions that test distinct consent abilities. These consent abilities are derived from psychiatric literature and case law and reflect four well-established standards (S) for decisional capacity: evidencing a choice for or against treatment (S1), appreciating the personal consequences of a treatment choice (S3), reasoning about treatment, or making a treatment choice based on rational reasons (S4), and understanding the treatment situation and choices (S5). The CCTI also assesses the capacity to make a reasonable choice (S2). This is an experimental standard that has not received legal or clinical acceptance due to arbitrariness in determining what constitutes a “reasonable” treatment choice. Administration time for the CCTI is about 20 to 25 minutes for both vignettes.

CCTI Scoring System

The CCTI has a detailed and well-operationalized scoring system that yields information regarding both capacity performance and capacity status. Capacity performance is the quantitative score that a patient receives for each standard. Scores across vignettes are summed to create a composite score for each standard. There is no CCTI total score.

Capacity status refers to the categorical outcome (capable, marginally capable, or incapable of consenting to treatment) obtained on a particular standard. Depending on the standard, capacity status on the CCTI is operationalized using either predetermined cut scores or psychometric cutoff scores derived from the performance of cognitively intact older adults. CCTI capacity outcomes must be used cautiously insofar as they are derived from cut scores and do not represent legal or clinical competency findings.

Reliability and Validity of the CCTI

The CCTI has reliability and validity as a measure of consent capacity. Three separate raters trained in administration and scoring of the CCTI achieved high interrater reliability for interval scales (>.83, p < .0001; S3-S5) and categorical scales (96% agreement; S1 and S2). The CCTI demonstrates face and content validity. The medical content of each vignette was reviewed and approved by a neurologist specializing in aging and dementia. The CCTI has been found to discriminate well between cognitively intact older adults and persons with both mild and moderate AD. The CCTI also discriminates well between older controls and patients with Parkinson’s disease and dementia. With respect to construct validity, factor analysis of the CCTI in an AD sample revealed a two-factor model of verbal reasoning and verbal memory, which was subsequently confirmed using neuropsychological factor analysis. In addition, the CCTI has demonstrated utility as a psychometric criterion for investigating the neurocognitive changes associated with loss of TCC.

Clinical and Research Utility

The CCTI provides a standardized and norm-referenced basis for evaluating TCC in individual patients and across different patient populations. For this reason, it has very good research application. In addition, by objectively evaluating different consent abilities, it pro-vides clinicians with flexibility in a particular case to consider different standards of capacity in relation to the risks and benefits of a particular treatment situation.

Limitations

The CCTI has three key limitations. First, because it uses standardized, hypothetical clinical vignettes (brain tumor, heart disease), the CCTI does not directly assess specific issues of TCC presenting clinically (e.g., in the treatment of bone cancer). Instead, it provides objective, norm-referenced information about a patient’s treatment consent abilities that the clinician can consider as part of his or her overall assessment of TCC. Thus, the CCTI gives up clinical specificity for standardization. A second limitation of the CCTI is its use of hypothetical medical vignettes. Patients dealing with real, personal medical problems arguably may display treatment consent abilities that differ somewhat from those demonstrated when responding to hypothetical medical situations. Finally, the CCTI and its performance and outcome scores are intended to support but not replace clinical judgment. Determination of consent capacity is ultimately a judgment made by a clinician.

References:

  1. Dymek, M., Marson, D., & Harrell, L. (1999). Factor structure of capacity to consent in Alzheimer’s disease. Journal of Forensic Neuropsychology, 1, 27-18.
  2. Griffith, R., Dymek, M., Atchison, P., Harrell, L., & Marson, D. (2005). Medical decision-making capacity in two neurodegenerative disorders: Mild AD and PD with cognitive impairment. Neurology, 65, 483-185.
  3. Marson, D. C., Dreer, L., Krzywanski, S., Huthwaite, J., DeVivo, M., & Novack, T. (2005). Impairment and partial recovery of medical decision-making capacity in traumatic brain injury: A six month longitudinal study. Archives of Physical Medicine and Rehabilitation, 86, 889-895.
  4. Marson, D. C., Ingram, K. K., Cody, H. A., & Harrell, L. E. (1995). Assessing the competency of patients with Alzheimer’s disease under different legal standards: A prototype instrument. Archives of Neurology, 52, 949-954.

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