Information and competency for consent to pharmacologic clinical trials in Alzheimer disease: an empirical analysis in patients and family caregivers

Abstract

This study was undertaken to evaluate (1) what information normal and Alzheimer disease (AD) participants are able to manage; (2) the correlation between the degree of competency and age, education and dementia scores, and the ability of dementia scores to predict incompetence; and (3) the capacity to retain consent-related information. To fulfil these aims, a four-point competency rating scale (1 = incompetent, 2 = marginally competent, 3 = sufficiently competent, and 4 = completely competent) was used in 70 patients (Mini-Mental State Examination [MMSE] score >9; Global Deterioration Scale score <6) and in 40 cognitively normal caregivers. Patients were divided into two subgroups (competency ratings 1 and 2 versus 3 and 4) to calculate positive and negative predictive values of MMSE and Alzheimer Disease Assessment Scale-cognitive (ADAScog) for absent/marginal competence. Main results were as follows: (1) 32.9% of AD patients were "incompetent" (no caregivers), 37.1% were "marginally competent" (20% caregivers), 18.6% were "sufficiently competent" (50% caregivers), and 11.4% were "completely competent" (30% caregiverss). (2) Competency ratings and age did not correlate in AD, whereas a negative correlation was significant in caregivers; competency ratings positively correlated to education in caregivers. (3) ADAScog and MMSE were the tests most significantly correlated to competency; MMSE score below 18 had a positive predictive value of 95% and a negative predictive value of 63.3%. The fact that 95% of patients with MMSE scores below 18 are incompetent or marginally competent points to an urgent need for ethical procedures capable of creating a balance between difficulties in obtaining valid consent and a patient's right to benefit from advances in clinical research.