Any experience with the P Tau 217 plasma test for Alzheimer's?

@flylgw

@gw1997 My husband had 3 skin biopsies.

What is the skin biopsy looking for?

The biopsy looks for an abnormal protein called alpha-synuclein.

Everyone has alpha-synuclein in their nerves. The problem is that in diseases like:

* Lewy body dementia (LBD)
* Parkinson’s disease
* Multiple system atrophy (MSA)

the protein becomes misfolded and clumps together. These clumps damage nerve cells.

The biopsy specifically looks for phosphorylated alpha-synuclein (P-SYN), which is the abnormal form associated with these diseases.

How is the biopsy done?

It’s very simple.

Usually three tiny (3 mm) punch biopsies are taken from different places, such as:

* the back of the neck
* above the knee
* near the ankle

The procedure:

* takes about 15–20 minutes
* uses local anesthetic
* generally doesn’t require stitches (or just one tiny stitch)

The samples are sent to a specialized lab where they are stained and examined under a microscope.

Why the skin?

Our skin contains small nerve fibers.

Those nerves are actually extensions of the nervous system, and in Lewy body diseases, the abnormal alpha-synuclein travels into these peripheral nerves—not just the brain.

So instead of trying to biopsy the brain (which isn’t done in living people), doctors can examine these skin nerves.

How accurate is it?

The test is very good, but not perfect.

Studies have found approximately:

* 90–95% sensitivity (it detects most people who truly have a synuclein disorder)
* 95–100% specificity (a positive result is very unlikely in people without one)

It’s one of the strongest biological tests currently available for confirming that a person has a synucleinopathy.

What does a positive result mean?

A positive biopsy means the person has a disorder involving abnormal alpha-synuclein.

By itself, the biopsy cannot distinguish between:

* Lewy body dementia
* Parkinson’s disease
* Parkinson’s disease dementia
* Multiple system atrophy

The doctor combines the biopsy with the person’s symptoms.

For Steve, because he has:

* progressive dementia,
* visual-spatial problems,
* fluctuations,
* parkinsonian features,
* and the positive skin biopsy,

those findings together strongly support Lewy body dementia rather than Alzheimer’s disease alone.

Why is this such a big deal?

Until recently, doctors diagnosed Lewy body dementia mostly from symptoms, and many people were misdiagnosed as having only Alzheimer’s disease.

The skin biopsy provides objective biological evidence that abnormal alpha-synuclein is present, giving families and clinicians much greater confidence in the diagnosis.

One important point

The biopsy doesn’t tell how severe the disease is or predict exactly how quickly it will progress. It answers a different question:

“Is there abnormal alpha-synuclein in the nervous system?”

For many families, having that answer can explain why symptoms such as hallucinations, cognitive fluctuations, parkinsonism, sensitivity to certain medications, and changes in attention occur together.

Knowing the biopsy was positive helps make sense of why his condition has features that don’t fit typical Alzheimer’s disease alone, and why his care team has been adjusting medications with Lewy body disease in mind.

@maryvc
I appreciate your comprehensive response.

Did your husband have a PET scan also?

If you feel comfortable in sharing, what medications is your husband on for the LBD?

@gw1997 Yes he has had PET scan and MRIs. He has Alzheimer’s as well so pretty severe mixed dementia. His Tau was .83.
Medications have been a challenge., He is very sensitive to meds.
Currently he is on Seroquil 12,5 mg morning and 25 mg at night. 3 times a day Klonopin. .125 mg
25 mg Trazadone at bedtime.
And for the ALZ/Lewy Body
Galantimine 8 mg twice a day.
He has periods of agitation during the day and the aids and nurses are very careful about agitating him.
It’s been a journey.
I hope this is helpful. I’m so sorry for him and all of us.

@maryvc I’m wondering if I should create another thread for the Lewy Body discussion.

@ocdogmom
I’m so sorry to hear of your husband’s vascular dementia.
What was your husband’s Ptau217? My husband’s is .44.
At first I thought that was very high. After reading some of the results on this forum, I realize it is outside of normal range for sure yet not near as high as others on here.
He has mild to moderate white matter disease diagnosed about 6 years ago. His most recent MRI shows brain volume loss and this may indicate vascular dementia. (VD). Do you know anything about how VD differs from Alzheimer’s? appreciate any insight.
We see his neurologist in about 3 weeks and I assume a PET scan will be ordered.

@lulululu
Yes, our primary care doctor ordered the Ptau217. I had to ask him for it though. It is fairly new; I believe FDA approved last year.
I believe we all have tau in our brains; the 217 bit is what delineates brain disease.

@gw1997 My husband's "interpretation likelihood score" was 0.0649 which indicates a low likelihood of amyloid plaque deposition in the brain. Low likelihood is any score below 0.3254
This test score combines the results of ABETA 42/40 and PTAU 217, not just the PTAU.
Brain volume loss is part of aging but can be accelerated by a number of things. I believe that my husband's two traumatic head injuries with subarachnoid and subdural bleeding is partly responsible for some of the volume loss. I believe that several other factors point to vascular dementia. His father had it (his mother had dementia as well but I don't know which kind) When my husband began to see significant memory loss his internist referred him to a neurologist for further evaluation and likely a PET scan of the brain. My husband who was a physician refused to see a neurologist because he said "they are only going to tell me what I already know" So he has not had a brain PET scan but has had CT scans with each head injury. His internist put him on Aricept several years ago. Hard to tell if it has slowed anything down. Vascular dementia is different than Alzheimer's in that it is usually caused by tiny blood clots in the smaller vessels of the brain. A heart arrhythmia can cause this. My husband had this arrhythmia in the past. Areas where the clot cuts off the flow of blood in the brain die and no longer function. I have learned that vascular dementia can present differently and progress differently than Alzheimer's. I would encourage you to learn as much as you can about dementia in general so that you can be better prepared for what is to come. I took some online live courses with Teepa Snow"s 'Positive Approach to Care" The "Champion series". It has helped me immensely. Not only did I learn about the different kinds of dementia (which is an umbrella term) but also how they likely will present at each stage and most important how to work with the skills your husband still has in each of the stages. Also important to learn is the ability to recognize the feelings that you will experience as you become more and more of your husband's caregiver and how to take care of yourself. Teepa Snow is an expert in the field of dementia caregiving. This is a great place to share your concerns and feelings. I have gotten so much support on this site. I hope you keep posting here. May God bless you and your husband.

@knottypine, welcome. Are you also caring for someone living with dementia?

I have my results from May 2025 - Sept 2025. I just turned 77 two weeks ago.
BLOOD TEST RESULTS
My PTAU217 was 6.05!! Quite high!
APOE result was E3/E4.
Beta Amyloid 42/40 ratio was 0.165.....very low!
My MRI and PET/SCAN results proved that I do indeed have ALZ. I was not surprised--- my father died from complications of ALZ at age 72.
I asked my Neurologist if it would help to have the Blood tests repeated after 1 year. He said it wouldn't help, and I can go along with that. I'm not doing any infusions due to the extreme side effects. Just diet and exercise, and keeping a good attitude. My wife is supportive, and does not need to help me. I was even able to do our fed and state taxes without help. My problems are balance, memory, and completing sentences.
I apologize if I rambled on too much.