UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

A tool to assess capacity to consent for treatment among homeless populations with problematic substance use Taylor, Darlene Lois


BACKGROUND: Individuals who misuse substances and who are homeless or unstably housed (IMSH) are at risk of acquiring communicable diseases such as HIV, sexually transmitted infections and blood-borne infections and have greater medical needs than the general population. However, obtaining informed consent for health care can be challenging as many IMSH have impaired cognition due to the effects of substances. This dissertation describes the development and validation process used to create a psychometric instrument that measures capacity to consent for health care (CTC-HC) among IMSH. METHODS: Forty-six qualitative interviews were conducted with 19 nurses who deliver care to IMSH and 27 IMSH to identify concepts that should be included in a capacity assessment instrument. A panel of experts reviewed possible items to obtain content and face validity. The instrument was administered to 302 IMSH. Construct and criterion validity were assessed by comparing the results of the new instrument to 1) a psychiatric assessment and 2) scores obtained from the MacArthur Competency Assessment Tool for Treatment. Item analysis was conducted to determine the reliability of the instrument and a confirmatory factor analysis was conducted. The areas under the receiver operating characteristic curves (ROC) were calculated to assess criterion validity. A diagnostic cut-off value was created using the corresponding points on the ROC. RESULTS: The final Capacity Assessment Instrument for People who misuse Substances (CAIPS) consists of items that address understanding, voluntariness, orientation, ability to communicate, sustained attention, distorted reality, appreciation, reasoning, expression of choice, decision making demands, and physical indication of substance use. These concepts were incorporated into an 11-item instrument that scores items on a four-point Likert scale. The CAIPS instrument demonstrated good internal reliability (Cronbach’s alpha: 0.861 – 0.893) and inter-observer reliability (weighted kappa statistic of 0.657). The factor analysis confirmed the unidimensionality assumption and the ROC analysis revealed that the CAIPS has a sensitivity of .75 - .81 and a specificity of .63 - .51. CONCLUSIONS: CAIPS is a reliable tool with moderate validity and is the first validated capacity assessment instrument available for clinicians to assess CTC-HC among IMSH.

Item Citations and Data


Attribution-NonCommercial-NoDerivs 2.5 Canada