Tests of Cognition and Rating Scales

Purpose of cognitive testing: to establish strengths and weaknesses of various functions relative to a standardised, norm-referenced scoring system, so that the nature and extent of cognitive deficits can be determined, informing diagnosis and management and acting as a comparator for past and future assessments.

A cognitive screen is not a diagnosis. The MMSE and similar tools give an overall assessment of cognitive function, but their use alone is not sufficient to establish a diagnosis of Alzheimer's disease or any dementia.

Cognitive screening is one of only two mandatory screens (with depression) in any older person with functional disability.

Key aspects of the mental status examination: state of consciousness · general appearance and behaviour · orientation · memory (short and long term) · language · visuospatial function · executive control functions · other cognitive functions (calculations, proverb interpretation) · insight and judgement · thought content · mood and affect.

Test all three components of memory: immediate recall (repeating digits), recent memory (recalling three objects after a few minutes), and remote memory (details of early life).

Executive function involves the planning, sequencing and execution of goal-directed activities, and is critical to the ability to perform IADLs. Screen with the clock-drawing test (a component of the Mini-Cog) or verbal fluency (listing 12 animal names in one minute is normal).

Interpretation depends on education and age. The MMSE score is dependent on sociocultural level and subject to a ceiling effect — a crucial caveat in the Indian population, where illiteracy is common.

Assess premorbid intellectual status where possible (for example the National Adult Reading Test) to interpret other test scores correctly.

Adapt tests to deficits. In language impairment or dyspraxia, recognition memory tests reduce the demand for expressive language required by recall tests.

Always include a standardised measure of mood — depression is the commonest mimic of cognitive impairment.

Recommended tools in primary care (Table 72.2): - Delirium: Confusion Assessment Method (CAM) - Dementia screening: AD8, Mini-Cog - Dementia assessment: SLUMS, MMSE, MoCA

Mini-Cog screens both memory (three-item recall) and executive function (clock drawing) — quick, and relatively education-independent.

MoCA and Addenbrooke's Cognitive Examination-Revised (ACE-R) are described as well-validated screening options; ACE-R incorporates the MMSE and clock-face drawing.

MMSE severity bands in Alzheimer's disease: mild 20–24, moderate 10–19, severe below 9.

Global staging scales combining cognition and ADLs: Global Deterioration Scale (GDS, Reisberg) and the Clinical Dementia Rating (CDR) scale.

Severe Impairment Battery (SIB) was developed for subjects too cognitively impaired for standard testing.

Memory-specific screens: the five-word test and the Memory Impairment Screen (MIS) assess anterograde verbal memory at an initial consultation. For detailed evaluation, free and cued recall paradigms — the Grober and Buschke test (Free and Cued Selective Reminding Test) and the California Verbal Learning Test — distinguish mild Alzheimer's disease from healthy subjects with more than 90% precision, even when MMSE scores are similar.

Domain-specific battery (Table 62.4 — Cardiff memory clinic):

Confusion Assessment Method (CAM) — the standard; sensitivity 94%, specificity 89% with high inter-rater reliability. Inattention is tested at the bedside by months of the year backwards, days of the week backwards, or digit span 3 or 4 backwards. - 3D-CAM: a structured three-minute screen — sensitivity 96%, specificity 86% in patients with dementia; 93% and 96% in those without. - Best single item: "months of the year backwards" (sensitivity 83%, specificity 69%). Best two items: months backwards plus "what is the day of the week?" (sensitivity 93%, specificity 64%). - CAM-ICU for intubated patients — inattention tested by squeezing on the letter A in "SAVEAHAART"; level of consciousness by RASS score other than 0.

Tests must be acceptable to the person and contain nothing belittling. Consent must be obtained, the purpose explained, and sensory and physical limitations accommodated — adequate lighting, earphone amplifiers, suitable seating, minimal distractions. Provide realistic reassurance with positively phrased feedback that highlights strengths as well as weaknesses, and at the end allow patients to comment on their own performance. Ideally an experienced psychologist or neuropsychologist performs formal testing, though much useful information can be obtained by any suitably trained professional. Introduce questions non-threateningly, because many patients with early deficits respond defensively.

2024 NIA-AA Revised Criteria — Alzheimer's disease is now defined biologically. Diagnosis rests on Core 1 biomarkers — a positive plasma p-tau217, a positive amyloid PET, or abnormal CSF ratios (p-tau181/Aβ42, t-tau/Aβ42, Aβ42/40). Cognitive testing now defines the clinical stage, not the disease itself. This is the single biggest conceptual change in the field.

Blood-based biomarkers have entered clinical use. Diagnostic models combining plasma p-tau217 with age and ApoE genotype achieve AUC around 0.94 for Alzheimer's disease. In very elderly nursing-home and hospital populations, plasma p-tau181, p-tau217 and GFAP differ significantly between cognitively normal and probable Alzheimer's groups, while Aβ42, Aβ40 and the Aβ42/40 ratio do not — an important practical point, since amyloid ratios perform poorly in the oldest old.

Cognitive screens are being repositioned as triage. Rather than diagnosing, MMSE and MoCA increasingly serve to decide who proceeds to biomarker testing. Clinical trials now use combinations such as CDR global score 0.5–1.0 plus MMSE 21 or above plus a positive Core 1 biomarker for entry.

Mild behavioural impairment (MBI) — late-onset persistent neuropsychiatric symptoms — has emerged as an early indicator of dementia risk that may precede measurable cognitive decline, and is being studied alongside plasma p-tau217.

Digital and mobile cognitive assessment. Mobile cognitive assessment systems have demonstrated diagnostic equivalence to MMSE and MoCA in Alzheimer's screening; future direction is composite risk scores combining digital tests, wearables and plasma p-tau217. Regulatory and ethical frameworks for data security, algorithmic transparency and equitable access are still being established.

Standardised inclusion in assessment frameworks. Cognition/delirium is one of the six mandatory core dimensions of the German S3 CGA guideline (2024); cognition is one of the six WHO ICOPE domains, with Mini-Cog, MoCA, MMSE or GPCOG named as step-2 assessment tools; Mentation is one of the 4Ms of Age-Friendly Health Systems.

Indian context. In LASI wave-1, impaired cognition was present in 9.3% of adults aged 60 and above. Culture- and education-fair instruments are essential: Hindi Mental State Examination (HMSE), Vernacular MoCA versions, Rowland Universal Dementia Assessment Scale (RUDAS), Indian Council of Medical Research Neuro-Cognitive Tool Box, and AIIMS Comprehensive Neuropsychological Battery in Hindi are used in place of a directly translated MMSE, because the standard MMSE penalises illiteracy heavily.