This protocol is based on ‘Neuropsychological tests for the diagnosis of Alzheimer’s disease dementia and other dementias: a generic protocol for cross-sectional and delayed-verification studies’ (Davis 2013).
Target condition being diagnosed
Dementia is a progressive syndrome of global cognitive impairment. In the UK, affecting 5% of the population over 65 years of age and at least 25% of those over 85 years of age (Alzheimer's Society 2007). Worldwide, 36 million people were estimated to be living with dementia in 2010 (Wimo 2010), and this number will increase to more than 115 million by 2050, with the greatest increases in prevalence predicted to occur in the developing regions. Dementia encompasses a group of disorders characterised by progressive loss of both cognitive function and ability to perform activities of daily living that can be accompanied by neuropsychiatric symptoms and challenging behaviours of varying type and severity. The underlying pathology is usually degenerative, and subtypes of dementia include Alzheimer’s disease dementia (ADD), vascular dementia, dementia with Lewy bodies, and frontotemporal dementia.
The target conditions in this review will be dementia (all-cause) and any dementia subtype (e.g. Alzheimer, vascular, Lewy body dementia).
The index test is the Montreal Cognitive Assessment (MoCA) (Nasreddine 2005) for all-cause dementia and its subtypes.
The MoCA takes 10 minutes to administer (Ismail 2010). It assesses short-term memory, visuospatial function, executive function, attention, concentration and working memory, language, and orientation. The MoCA is regarded as an alternative to the Mini-Mental State Examination (MMSE) (Folstein 1975) since the latter is now copyrighted and there is a charge for its use. It is also considered to offer more detailed testing of executive function than the MMSE.
The MoCA is scored out of 30 points. The raw score is adjusted by educational attainment (1 extra point for 10 to 12 years of formal education; 2 points added for 4 to 9 years of formal education). A score of 26 or above is considered normal. A score below 26 indicates possible dementia. Any application of a different threshold will be noted in the analyses.
Three versions of the MoCA exist in English to minimise practice effects. Multiple translations are also available, as is a version for visually impaired persons (Wittich 2010). It is available online (www.mocatest.org).
Dementia usually develops over several years. Individuals, or their relatives, may notice subtle impairments of recent memory. Gradually, more cognitive domains become involved, and difficulty in planning complex tasks becomes increasingly apparent. Figure 1 gives an overview of a range of pathways through which individuals may present.
It is vital to appreciate that the pathway to dementia diagnosis influences the diagnostic test accuracy of the MoCA. This protocol will therefore separate the DTA analyses by population tested. Presenting the findings of the review by population emphasises that the utility of the test differs across different patient settings, and guidance is needed to decide where and how the test would best be used.
Developed in 2005, evidence for the utility of the MoCA in different settings is still emerging. Most diagnostic accuracy studies are likely to have been conducted in specialist clinics, and evidence is required for its use in hospital inpatient settings, in general outpatient settings, in primary care, and as a population screening tool. This protocol therefore stratifies all analyses based on the following four populations:
Those with no memory complaints (population screening);
Those presenting to primary care practitioners with subjective memory problems that have not been previously assessed;
Those referred to a secondary care clinic for the specialist assessment of memory difficulties;
Those tested during acute admission to a general hospital.
The severity (stage) of dementia at diagnosis will influence the utility of the MoCA. In later stages of the disorder, scores will be more specific for dementia, and MoCA may be used to aid diagnosis. In the earlier stages, lower scores will be more sensitive to dementia and MoCA may be used as a screening test.
In the UK, people usually first present to their general practitioner (Figure 1). One or more brief cognitive tests (including the index test) may be administered, and might result in a referral to a memory clinic for specialist diagnosis (Boustani 2003; Cordell 2013; Alzheimer's Society 2013).
However, many people with dementia may not present until later in the disorder and may follow a different pathway to diagnosis, e.g. referral to a community mental health team for individuals with complex problems otherwise unable to attend a memory clinic. Others may be identified during an assessment for an unrelated physical illness, e.g. during an outpatient appointment or an inpatient hospital admission.
In general, the role of non-specialist community services in dementia diagnosis is to recognise possible dementia and to refer on to appropriate care providers, though this may vary geographically (Greening 2009; Greaves 2010). Some community settings have a higher prevalence of dementia than others. For example, the pretest probability of prevalent dementia among residents in care homes is much higher than in the general population (Matthews 2002; Plassman 2007). This has led some to suggest that a cognitive assessment is made routinely for every person resident or admitted to a care home (Alzheimer's Society 2013). Through such an active case-finding strategy, a dementia diagnosis might be made outside the usual pathway.
Diagnostic assessment pathways vary across different countries, and diagnoses may be made by a variety of healthcare professionals including general practitioners, neurologists, psychiatrists, and geriatricians; thus we shall describe the target populations rather than the exact setting in order to facilitate generalisability of the results.
How might the index test improve diagnoses, treatments and patient outcomes?
The MoCA test may help identify people requiring specialist assessment and treatment for dementia. Some symptomatic treatments and cognitive-behavioural interventions are available (Birks 2006; McShane 2006; Bahar-Fuchs 2013). Furthermore, dementia diagnosed at an early stage can help patients, their families and potential carers access appropriate services and make timely plans for the future. Improved diagnostic accuracy might also reduce false positive diagnoses, which carry risk of significant costs (in the form of further unnecessary investigations or treatment) and harm (from side effects of investigations or treatment, or anxiety).
Outcomes for people with dementia in secondary care general hospital settings, including survival, length of stay and discharge to institutional care, are poor (RCPsych 2005; Sampson 2009; Zekry 2009) Accurate diagnosis may have specific benefits in addressing these adverse outcomes, in addition to facilitating access to the most suitable care and the use of non-pharmacological methods to manage behavioural and psychological symptoms of dementia.
The general rationale for the accurate diagnosis of dementia is detailed in the generic protocol (Davis 2013). Since the publication of the generic protocol, wide-ranging changes in policy with respect to case-finding and/or screening for dementia have resulted in an urgent need to evaluate the utility of the commonly-used cognitive tests for dementia.
Although dementia screening itself is not recommended by the United States Preventative Services Task Force (Boustani 2003) or the UK National Screening Committee, there appears to be a drift towards the opportunistic testing of older primary care attenders who have presented for reasons other than a memory complaint (Brunet 2012). The UK government has already incentivised screening for dementia on acute admission to secondary care service, and has proposed incentivising the identification of dementia in people in primary care settings (Dementia CQUIN 2012). In the USA, the Patient Protection and Affordable Care Act (2010) added an Annual Wellness Visit, which includes a mandatory assessment of cognitive impairment (Cordell 2013). With such strong policy drivers in play, the diagnostic test accuracy of the MoCA must be established, both in people who have presented with a memory problem and in those who are tested as part of a general ‘check-up’.