What is the diagnostic approach for an older adult with suspected dementia?

Diagnostic Approach for Dementia in Older Adults

Diagnose dementia through a structured clinical evaluation that includes corroborative informant history using validated tools (AD8, IQCODE, or Quick Dementia Rating System), objective cognitive testing with standardized instruments (MoCA or MMSE), functional assessment to confirm interference with daily activities, targeted laboratory testing to exclude reversible causes, and brain MRI to identify structural pathology. 1, 2, 3

Step 1: Obtain Corroborative Informant History

• Always obtain history from a reliable informant (family member or close friend) using structured validated tools such as the AD8, IQCODE (Informant Questionnaire on Cognitive Decline in the Elderly), or Alzheimer's Questionnaire to assess changes in cognition, function, and behavior. 1, 2, 3
• Document baseline functioning and compare with current functioning to establish decline over time. 2
• Assess the four key domains systematically: cognition (memory, orientation, problem-solving), daily function (IADLs and ADLs), mood and behavior (depression, apathy, agitation), and sensorimotor function (gait, vision, hearing). 1

Critical pitfall: Relying solely on patient self-report without informant corroboration leads to missed diagnoses due to lack of insight in dementia patients. 2

Step 2: Perform Objective Cognitive Testing

• Administer the Montreal Cognitive Assessment (MoCA) for suspected mild dementia or the Mini-Mental State Examination (MMSE) for moderate dementia. 2, 3, 4
• The MMSE uses a cut point of 23/24 or 24/25 (score considered "positive"/"negative") for most primary care populations, though sensitivity and specificity vary by age and education level. 1
• Add the Clock Drawing Test as a supplementary assessment for visuospatial and executive function. 2
• The Mini-Cog test and Addenbrooke's Cognitive Examination-Revised (ACE-R) have comparable diagnostic performance to MMSE (Mini-Cog: 0.91 sensitivity and 0.86 specificity; ACE-R: 0.92 sensitivity and 0.89 specificity). 4

Key distinction: If cognitive testing is inconclusive (symptoms present but normal examination findings), refer for formal neuropsychological testing to establish the extent and severity of cognitive impairment objectively. 2, 5

Step 3: Assess Functional Status

• Evaluate impact on instrumental activities of daily living (IADLs): managing finances, medication management, transportation, household management, cooking, and shopping abilities. 2, 3
• Use structured tools like the Pfeffer Functional Activities Questionnaire (FAQ), Disability Assessment for Dementia (DAD), Lawton IADL Scale, or ECog. 2
• Dementia requires significant interference with daily functioning, whereas mild cognitive impairment affects only complex IADLs without impacting basic ADLs. 2, 3

Step 4: Core Laboratory Testing

Obtain the following tests to exclude reversible causes of cognitive impairment: 3, 6

• Complete blood count (CBC)
• Comprehensive metabolic panel (especially sodium, calcium, glucose)
• Thyroid-stimulating hormone (TSH) and free T4
• Vitamin B12 and folate levels
• Liver function tests
• HIV testing if risk factors present 2

Evidence note: A careful history and physical examination accompanied by CBC, chemistry battery, and thyroid function test is effective in diagnosing treatable illnesses causing cognitive impairment, with other tests used selectively based on examination findings. 6

Step 5: Structural Neuroimaging

• Brain MRI without contrast is strongly recommended over CT, particularly for detecting vascular lesions, white matter disease, medial temporal lobe atrophy, tumors, hydrocephalus, and hemorrhages. 1, 2, 3, 7
• MRI is especially indicated with: onset of cognitive symptoms within past 2 years, unexpected decline in cognition/function, recent significant head trauma, unexplained neurological manifestations, or significant vascular risk factors. 2

Contemporary practice note: Structural neuroimaging now serves not only to exclude non-neurodegenerative etiologies (tumors, inflammatory conditions, infections) but also to identify atrophy patterns characteristic of specific dementia subtypes. 1

Step 6: Physical and Neurological Examination

• Perform a comprehensive physical examination with specific attention to findings suggesting underlying medical contributors. 1
• Conduct a dementia-focused neurological examination assessing: focal neurologic abnormalities (suggesting stroke), gait speed and motor movements, reflexes and Babinski signs, and extrapyramidal signs (suggesting Lewy body dementia or Parkinson's disease dementia). 2, 5

Step 7: Assess for Common Contributors and Comorbidities

Systematically evaluate for conditions that can exacerbate or mimic dementia: 1, 2, 3

• Sensory deficits: hearing loss, vision loss, depth perception changes
• Sleep disorders: particularly obstructive sleep apnea
• Medications: review all medications to identify and minimize anticholinergic or sedative medications that worsen cognition
• Metabolic disturbances: electrolyte abnormalities, hypoglycemia/hyperglycemia, B12 or folate deficiencies, thyroid dysfunction, anemia
• Mood disorders: depression can cause symptoms similar to dementia and can co-occur with early dementia
• Pain: undiagnosed or undertreated pain
• Vascular risk factors: stroke/TIA, hypertension, diabetes, hypercholesterolemia

Important consideration: Most individuals older than age 80 with cognitive impairment harbor more than one type of brain pathological change, resulting in "mixed etiology dementia." 1

Step 8: Synthesize Diagnostic Formulation

• Integrate information about risk profile, history of symptoms, and examination findings to determine: (1) whether cognitive-behavioral syndrome is present, (2) the severity level (mild cognitive impairment vs. dementia), and (3) the most likely etiology. 1
• Core diagnostic criteria for dementia: cognitive or behavioral symptoms that interfere with ability to function at work or usual activities, represent a decline from previous functioning, and are not explained by delirium or major psychiatric disorder. 2

Step 9: Consider Biomarkers in Atypical Cases

For atypical presentations (age of onset <65 years, rapid symptom onset, prominent non-memory cognitive domains, or diagnostic uncertainty after initial workup), consider: 1, 5

• Cerebrospinal fluid assays for amyloid beta and tau proteins
• Amyloid PET or tau PET imaging
• Genetic testing for familial forms
• Referral to memory clinic or dementia subspecialist 3

2025 NIA-AA framework: Biomarker evidence of both amyloid beta (PET or CSF) and neuronal injury (structural MRI, FDG PET, CSF tau) increases certainty that dementia is due to Alzheimer's disease pathophysiology. 1

Step 10: Establish Follow-Up and Monitoring Plan

• Schedule follow-up visits every 6-12 months with serial cognitive assessments (MMSE or MoCA) to document progression and monitor treatment response. 2, 3
• Use a multi-dimensional approach assessing cognition, functional autonomy, behavioral symptoms (using NPI-Q or MBI-C), and caregiver burden. 2
• More frequent visits are warranted if behavioral symptoms emerge. 3

Common pitfall: Failing to use standardized, validated instruments reduces diagnostic accuracy and makes longitudinal tracking unreliable. 2