Screening and treatment for Alzheimer's disease: Predicting population‐level outcomes

Screening for preclinical Alzheimer's disease: Deriving optimal policies using a partially observable Markov model

Alzheimer's Disease (AD) is believed to be the most common type of dementia. Even though screening for AD has been discussed widely, there is no screening program implemented as part of a policy in any country. Current medical research motivates focusing on the preclinical stages of the disease in a modeling initiative. We develop a partially observable Markov decision process model to determine optimal screening programs. The model contains disease free and preclinical AD partially observable states and the screening decision is taken while an individual is in one of those states. An observable diagnosed preclinical AD state is integrated along with observable mild cognitive impairment, AD and death states. Transition probabilities among states are estimated using data from Knight Alzheimer's Disease Research Center (KADRC) and relevant literature. With an objective of maximizing expected total quality-adjusted life years (QALYs), the output of the model is an optimal screening program that specifies at what points in time an individual over 50 years of age with a given risk of AD will be directed to undergo screening. The screening test used to diagnose preclinical AD has a positive disutility, is imperfect and its sensitivity and specificity are estimated using the KADRC data set. We study the impact of a potential intervention with a parameterized effectiveness and disutility on model outcomes for three different risk profiles (low, medium and high). When intervention effectiveness and disutility are at their best, the optimal screening policy is to screen every year between ages 50 and 95, with an overall QALY gain of 0.94, 1.9 and 2.9 for low, medium and high risk profiles, respectively. As intervention effectiveness diminishes and/or its disutility increases, the optimal policy changes to sporadic screening and then to never screening. Under several scenarios, some screening within the time horizon is optimal from a QALY perspective. Moreover, an in-depth analysis of costs reveals that implementing these policies are either cost-saving or cost-effective.

[Validation of RUDAS: A screening tool for dementia in Primary Health Care settings]

Objetivo

Validar la escala Rowland Dementia Assessment Scale (RUDAS) como instrumento de cribado de deterioro cognitivo y demencia en atención primaria (AP). Es un test breve, válido para población con bajo nivel educativo formal y fácilmente traducible en entornos multiculturales.

Diseño

Se realizó un estudio epidemiológico descriptivo, de corte transversal, con seguimiento a los 5 años.

Emplazamiento

Centro de salud de atención primaria de O Grove, que atiende a una población de 10.650 habitantes en Pontevedra.

Participantes

Ciento cincuenta personas aleatoriamente seleccionadas, con una edad media de 76,35 ± 7,12 años, bajo nivel educativo, origen predominantemente rural y semirrural y nivel socioeconómico bajo.

Intervención

Se analizó la viabilidad, la aceptabilidad, la validez y la fiabilidad de la escala.

Mediciones principales

RUDAS, Mini Mental State Examination, Clinical Dementia Rating, Índice de Katz, Índice de Barthel, Índice de Lawton y Escala de Depresión Geriátrica de Yesavage.

Resultados

El test fue bien acogido por los pacientes y rápido de aplicar (7,58 ± 2,10 min). El área bajo la curva COR para el diagnóstico de demencia fue 0,983 (IC 95%: 0,97-1,00). Para un punto de corte óptimo de 22,5 presentó una sensibilidad del 89,3% y una especificidad del 100%. El área bajo la curva COR para discriminar personas con DCL de personas con demencia fue 0,965 (IC 95%: 0,91-1,00).

Conclusiones

El RUDAS ha demostrado ser un instrumento viable y eficiente para cribar demencias en AP, libre de influencias educativas y socioculturales. Es especialmente sensible para discriminar población con deterioro cognitivo leve de población con demencia.

ELECTRONIC DEVICES FOR COGNITIVE IMPAIRMENT SCREENING: A SYSTEMATIC LITERATURE REVIEW

OBJECTIVES

The reduction in cognitive decline depends on timely diagnosis. The aim of this systematic review was to analyze the current available information and communication technologies-based instruments for cognitive decline early screening and detection in terms of usability, validity, and reliability.

METHODS

Electronic searches identified 1,785 articles of which thirty-four met the inclusion criteria and were grouped according to their main purpose into test batteries, measures of isolated tasks, behavioral measures, and diagnostic tools.

RESULTS

Thirty one instruments were analyzed. Fifty-two percent were personal computer based, 26 percent tablet, 13 percent laptop, and 1 was mobile phone based. The most common input method was touchscreen (48 percent). The instruments were validated with a total of 4,307 participants: 2,146 were healthy older adults (M = 73.59; SD = 5.12), 1,104 had dementia (M = 74.65; SD = 3.98) and 1,057 mild cognitive impairment (M = 74.84; SD = 4.46). Only 6 percent were administered at home, 19 percent reported outcomes about usability, and 22 percent about understandability. The methodological quality of the studies was good, the weakest methodological area being usability. Most of the instruments obtained acceptable values of specificity and sensitivity.

CONCLUSIONS

It is necessary to create home delivered instruments and to include usability studies in their design. Involvement of people with cognitive decline in all phases of the development process is of great importance to obtain valuable and user-friendly products. It would be advisable for researchers to make an effort to provide cutoff points for their instruments.