Does a borderline result on the Montreal Cognitive Assessment (MoCA) in an older adult indicate mild cognitive impairment?

Does a Borderline MoCA Score Indicate Mild Cognitive Impairment?

A borderline MoCA score does not definitively indicate mild cognitive impairment (MCI) and requires comprehensive clinical evaluation including functional assessment, informant reports, and exclusion of reversible causes before making this diagnosis. 1

Understanding the Diagnostic Limitations of Borderline MoCA Scores

The MoCA is a screening tool, not a diagnostic instrument. The distinction between MCI and dementia must be made on the basis of clinical assessment of cognition AND function, not screening scores alone. 1 A borderline score (typically 23-25 out of 30) indicates the need for further evaluation but cannot establish the diagnosis of MCI by itself.

Why Borderline Scores Are Diagnostically Ambiguous

• The MoCA demonstrates high sensitivity (93%) but modest specificity (37-77%) in clinical settings when using referred patients as comparisons rather than healthy controls 2
• A score below 26 has only 33% positive predictive value for MCI in old age psychiatry settings, meaning two-thirds of patients with borderline scores do not have MCI 2
• Conversely, a score ≥26 has 94% negative predictive value, making it excellent for ruling out MCI 2
• Practice effects can artificially inflate MoCA scores on repeated testing, masking underlying cognitive decline in individuals with MCI 3

Required Components for MCI Diagnosis Beyond Screening

You must complete a multi-component assessment before diagnosing MCI: 1, 4

1. Objective Cognitive Assessment

• Administer comprehensive neuropsychological testing beyond the MoCA, as this is the gold standard for demonstrating cognitive deficits 4
• Test specific domains including memory (Trail Making Test), executive function, language (Boston Naming Test), and visuospatial skills 4

2. Functional Evaluation

• Use validated functional assessment tools such as the Pfeffer Functional Activities Questionnaire (FAQ) or Disability Assessment for Dementia (DAD) to determine if the patient maintains independence in instrumental activities of daily living 1
• MCI requires preserved functional independence; significant functional impairment indicates dementia rather than MCI 4

3. Informant Report

• Obtain collateral history using structured instruments like the Ascertain Dementia 8 (AD-8) questionnaire or Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) 1
• Combining cognitive tests with functional screens and informant reports improves diagnostic accuracy 1

4. Systematic Exclusion of Reversible Causes

• Review all medications for anticholinergic burden (first-generation antihistamines, muscle relaxants, oxybutynin, tricyclic antidepressants) 5
• Order essential laboratory tests: complete blood count, comprehensive metabolic panel, TSH, vitamin B12, hemoglobin A1C 5, 4
• Screen for depression systematically, as it commonly presents with cognitive complaints and can mimic MCI 5, 6
• Consider infections (urinary tract infections, pneumonia), metabolic disturbances, and substance use 5, 6

5. Neuroimaging

• Obtain MRI brain (preferably with and without contrast) to detect vascular changes, structural lesions, and patterns of neurodegenerative disease 4

Common Pitfalls to Avoid

• Do not diagnose MCI based solely on a borderline MoCA score without completing functional assessment and excluding reversible causes 1, 4
• The MoCA was validated primarily using healthy controls as comparisons, which overestimates specificity in real clinical populations 2
• Repeated MoCA testing can produce falsely reassuring scores due to practice effects, even as underlying cognitive function deteriorates 3
• The MMSE lacks sensitivity for MCI detection; if MMSE is in the "normal" range (24+) but clinical suspicion remains, the MoCA should be administered 1

Clinical Algorithm for Borderline MoCA Scores

When encountering a borderline MoCA score (23-25/30):

1. Obtain detailed informant report using AD-8 or IQCODE 1
2. Assess functional independence using FAQ or DAD 1
3. Review medications and discontinue anticholinergics 5
4. Order laboratory evaluation (CBC, CMP, TSH, B12, HbA1c) 5, 4
5. Screen for depression using PHQ-9 1
6. Obtain brain MRI 4
7. Consider formal neuropsychological testing for definitive cognitive domain assessment 4
8. Schedule follow-up in 2-4 weeks to review results and repeat cognitive testing 5

If functional independence is preserved, reversible causes are excluded, and objective cognitive impairment is confirmed on comprehensive testing, then MCI diagnosis can be established. 4 If functional impairment is present, consider dementia rather than MCI. 1