A cognitive test score or an Alzheimer's blood test came back. What does it mean?

What does a MoCA test score mean, and what does it not measure?

A MoCA score measures how a person performed on a short set of thinking tasks on one day. The MoCA, short for Montreal Cognitive Assessment, is a ten-minute, 30-point screening test that samples memory, attention, language, visual and spatial skill, and executive function, the planning and organizing side of thinking. It was built to flag possible mild cognitive impairment, not to diagnose it [PMID: 15817019].

The original study used a cutoff of 26, and at that level the test picked up 90 percent of people with mild cognitive impairment [PMID: 15817019]. Later work found that 26 flags too many healthy people, especially older adults and those with fewer years of education, and a pooled analysis found that 23 gave better overall accuracy [PMID: 28731508]. A 24 can be an ordinary result for one person and a real change for another.

What the score does not show is why. Poor sleep, low mood, anxiety on the day, hearing or vision trouble, pain, medications and testing in a second language all lower scores. A screening score also cannot rule out a problem in someone who has noticed a genuine change, particularly a person who started from a high level.

What does an Alzheimer's blood test such as p-tau 217 measure, and what does it not?

A p-tau 217 test measures a form of tau, a protein found inside nerve cells, that rises in the blood when amyloid plaques and tau tangles, the two protein deposits that define Alzheimer's disease, are building in the brain. In research cohorts the blood level identified abnormal amyloid and tau with accuracy comparable to spinal fluid testing [PMID: 38252443].

It measures biology, not function. It does not test memory, does not say what is causing a symptom, and cannot say whether or when dementia will follow. Most people who have amyloid in the brain without symptoms will not develop Alzheimer's dementia in their lifetime [PMID: 29802030].

The number also has technical limits. Results are often reported in three ranges, and in one study about a fifth fell in a middle range that needed confirmation by PET scan or spinal fluid testing [PMID: 38252443]. Other conditions move the level: in a community study, chronic kidney disease shifted it about as much as brain amyloid did [PMID: 35618838]. Among people without symptoms, about one in five positive results was not confirmed on PET or spinal fluid testing [PMID: 40952756].

That is why the test sits inside a clinical evaluation. The first blood test the FDA cleared to aid in diagnosing Alzheimer's disease, in 2025, is for adults 55 and older who have signs and symptoms, and is not intended for screening or as a stand-alone diagnosis [Source: FDA 2025 news release, first blood test used in diagnosing Alzheimer's disease]. The Alzheimer's Association guideline places these tests within a full diagnostic workup of people with measurable cognitive impairment in specialized care, and notes that accuracy varies considerably between tests [PMID: 40729527].

What does a mild cognitive impairment label mean, and what comes next?

Mild cognitive impairment, or MCI, means thinking has measurably declined beyond what is expected for age while the person still manages daily life independently. It describes a level of function, not a cause, and it is not dementia.

The outlook is more varied than the label suggests. In a meta-analysis of 89 studies with about five years of follow-up, around half of people with MCI stayed stable. Between 27 and 42 percent progressed to dementia, the higher figure coming from specialist clinics, and in community studies more than a quarter returned to normal cognition [PMID: 40078377]. Which path a person takes depends heavily on the cause, so the label opens the workup and does not close it.

Why establish a brain-health baseline?

A baseline turns a single score into a trend. A cognitive result is most useful when compared with the same person's earlier performance, because people start from very different levels and a population cutoff cannot see a decline from a high starting point.

A baseline usually pairs a standardized cognitive measure with the physical numbers that shape brain health over decades: blood pressure, blood sugar and insulin, lipids, sleep quality and hearing. Inherited risk can be part of it for those who want to know, a choice covered in what a genetic risk result changes. When a screening test is too blunt, formal neuropsychological testing, a longer battery given by a psychologist who specializes in how the brain affects thinking, compares each skill with norms for age and education.

What does a physician do after a low score or a positive blood test?

A physician starts with the contributors that can be treated, then decides whether the pattern calls for a specialist.

• Sleep. Short or broken sleep and untreated sleep apnea, repeated pauses in breathing during sleep, blunt attention and memory.
• Thyroid and vitamin B12. Both are checked with a blood test, and both can slow thinking when low.
• Medications. Sedating medications and those with anticholinergic effects, meaning they block a chemical messenger involved in memory, are reviewed with the clinicians who manage them.
• Mood. Depression and anxiety can look like memory loss and are treatable in their own right.
• Hearing. Hearing loss strains attention, and a Lancet Commission review notes that hearing aids appear to reduce the excess dementia risk tied to it [PMID: 32738937].
• Vascular and metabolic health. Blood pressure, blood sugar and lipids are measured and managed, as the cognitive decline guide describes.

Referral to neurology or a memory clinic follows when impairment is confirmed on testing, when decline continues after those contributors are addressed, when the person is young for such changes, or when the pattern is unusual, such as early changes in language, behavior, movement or vision. Brain imaging, neuropsychological testing and biomarker tests are usually arranged there, and the primary physician stays involved to coordinate.

When does a change in thinking need prompt care?

A score is not an emergency, but a sudden change is. Sudden confusion, trouble speaking or understanding, a drooping face, weakness or numbness on one side, loss of vision or a severe sudden headache are reasons to call 911 or go to the nearest emergency department. Confusion that develops over hours or days, especially with a fever, a new medication, or a recent fall or head injury, needs medical care the same day.

Can a cognitive test or blood test ordered without a physician be reviewed?

Yes. A score from an online or app-based cognitive test, or a blood biomarker result from a service a person ordered on their own, is reviewed as part of care. The full report helps: the name of the test, the date, the laboratory and its reference ranges, and any earlier scores. An account from someone who knows the person well often adds what no test captures.

The deeper picture

Both kinds of result measure one slice of a long process. Alzheimer's biology can be present for years without symptoms, and symptoms often have causes that are not Alzheimer's disease at all, frequently several at once: vascular change, sleep, mood, medications, hormones and metabolic health. The clinical skill lies in keeping two questions apart, how a person's thinking is working and what biology sits underneath it, and then reading them together. Doing that with physician-level clinical rigor and one person's full history is how Dr. Paul approaches a result like this.