A 4-Item Instrument for assessing Capacity to Consent to Research among Older Adults

Background: There is an increasing interest in developing practical measures for assessing the capacity of older adults to consent to research (Moye & Marson, 2007). The capacity tends to be questioned more often as individuals age. However, there are few studies on developing reliable and validated brief instruments to evaluate whether older adults have the capacity to consent to research or not.

Propose: The aim of this study is to develop and validate an assessment tool for research consent competence for older participants. It is designed to have at least three strengths that the scale could be brief and easy-to-use, be reliable and valid, and include four dimensions of capacity to consent to research (evidencing a choice, understanding, reasoning, and appreciation).

Method: A 4-item instrument was developed to assess the capacity of older adults to consent to research. Each item was rated on a two-point scale (0=wrong, 1= correct). The scale included one item for understanding, one item for appreciation, one item for reasoning, and one item for evidencing a choice on the basis of the provided information for the study. The four questions adapted from Capacity-to-Consent Tool (CCT) developed by Zayas, Cabass, and Perez in 2005. Information was obtained from 203 nursing home residents from two facilities and 201 community-dwelling older adults in a metropolitan city in South Korea. Internal consistency, concurrent validity, and convergent validity were tested. In addition, a confirmatory factor analysis was conducted to confirm the acceptability of the model fit of one factor with four items.

Results: The reliability of the 4-item scale was very good (α=.85). All of the item-total correlations were greater than .50. Claims for convergent validity were supported because the 4-item questionnaire total scores were significantly correlated with scores of cognitive abilities in the sample (r=.480, p < .001). The scale was strongly correlated with CCT scores for a study (r=.939, p < .001). The sensitivity and specificity of the 4-item instrument were calculated by comparing the results of the CCT scores: the sensitivity was 99.0% and the specificity was 84.8%. The model fit of one factor with four items was good, with SRMR= .024, NNFI= .98, CFI = .99, and IFI= .99.

Conclusions and Implication: The results confirmed that the 4-item instrument for assessing the capacity of older adults to consent to research had good internal consistency, convergent and concurrent validity, and acceptable model fit. The short form can be used for gerontological researchers to assure their older participants to have the capacity to consent to research in informed consent process.

Moye, J., & Marson, D. C. (2007). Assessment of decision-making capacity in older adults: An emerging area of practice and research. Journal of Gerontology: Psychological Sciences, 62B(1), P3-P11.

Zayas, L. H., Cabassa, L. J., & Perez, M. C. (2005). Capacity-to-consent in psychiatric research: Development and preliminary testing of a screening tool. Research on Social Work Practice, 15(6), 545-556.