"Doctor, my mom has been forgetting things a lot recently. Could it be Alzheimers disease?"
"Doctor, the PET scan is too expensive. Is there any other way to make a definite diagnosis?"
Clinically, many patients encounter similar problems. The high cost and invasiveness of traditional AD diagnostic methods have caused many patients to miss the golden window period for early intervention. Today, we have good news to share: just one tube of blood can accurately detect Alzheimers disease (AD)! This disruptive technology is rewriting the diagnosis and treatment landscape of AD.
1
From the Brain to the Blood: Why Can It Be a "Precise Signal"?
Two "culprits" of Alzheimers disease are hidden in the brain: one is amyloid protein plaques (like "garbage" blocking nerves), and the other is tau protein tangles (abnormal structures that damage neurons).
Among them, when tau protein is "activated" in a special way, it forms "p-tau217" - this substance will, as the disease progresses, penetrate the brains "protective barrier" (blood-brain barrier) and seep into the bloodstream.
For instance, p-tau217 is like the "fingerprint" left by Alzheimers disease in the blood: it only recognizes one disease. It significantly increases in the blood of Alzheimers patients but remains almost unchanged in other forms of dementia (such as frontotemporal dementia), which enables it to precisely distinguish between different diseases.
The amount of p-tau217 in the blood is almost perfectly synchronized with the severity of tau protein tangles in the brain. Just like a blood test can "see" the brain lesions, the condition can be known without opening the skull.
2
Where does the data of over 90% accuracy come from?
Why is the p-tau217 blood test reliable? More than 20 research teams worldwide (including large-scale cohorts from Sweden, Canada, and China) have verified its effectiveness.
Sensitivity 90%+: At least 90 out of 100 Alzheimers patients can be detected by it, with very few cases of missed diagnosis.
Specificity of over 90%: Among 100 people without Alzheimers disease (such as healthy elderly individuals or patients with other forms of dementia), it can accurately rule out at least 90, with very few misdiagnoses.
For instance, a study in Sweden found that by combining a blood test for p-tau217 with information such as age and family history, the accuracy rate for determining whether there is amyloid protein deposition in the brain can reach 97%, which is much more reliable than a doctors diagnosis based solely on symptoms (with an accuracy rate of 60% to 70%).
The data from our multi-center longitudinal study on cognitive decline in China (SILCODE) also supports the new criteria, showing that among the plasma markers, only p-tau217 has an accuracy consistent with Aβ PET at around 90%.
3
Why was it included in the international guidelines?
The 2024 guidelines released by the Alzheimers Association in the United States officially recognize the p-tau217 blood test as "clinical diagnostic evidence", and there are three solid reasons behind this:
Early enough: Abnormal p-tau217 can be detected in the blood 10 to 20 years before patients experience memory decline, providing time for early intervention.
Accurate enough: Numerous studies have confirmed that its accuracy far exceeds the traditional "guessing the disease based on symptoms", transforming diagnosis from "relying on experience" to "depending on data".
Its practical enough: compared with the old method, it is more suitable for ordinary people.
4
What are its advantages over traditional checks?
In the past, the methods for diagnosing Alzheimers disease posed a great challenge for many families:
Cerebrospinal fluid examination: It involves extracting fluid from the lower back (lumbar puncture). Elderly people are afraid of the pain, infection and the need to be hospitalized. Many people are reluctant to undergo it.
A PET scan costs around 3,000 to 16,000 yuan each time and involves exposure to a small amount of radiation. It is difficult for ordinary families to afford and few primary hospitals have the equipment.
✅ And the p-tau217 blood test has completely solved these problems:
✅ Non-invasive: Just like a routine blood draw during a physical examination, only 0.5 milliliters of venous blood is needed. It is easily accepted by the elderly.
✅ Affordable price: Many domestic hospitals have already launched this service, with each session costing approximately 300 to 800 yuan (currently at your own expense).
Convenient and fast: No hospitalization is required. After blood is drawn, it is analyzed in the laboratory, and the results are available within a few days.
5
Who should have this test? Is the process complicated?
Three types of people are especially recommended to get checked:
1. Over 50 years old, often forgetful and absent-minded (for instance, forgetting what was just said as soon as the conversation moves on).
2. There is a family member with Alzheimers disease at home (the risk is higher if a direct relative is affected);
3. People who have already undergone PET or cerebrospinal fluid tests and want to further confirm their condition.
The inspection process consists of just three steps:
The doctor first assesses: asks about symptoms and family history, and determines whether tests are needed.
2. Blood test: A small amount of venous blood is drawn for laboratory analysis of the content of p-tau217.
3. Comprehensive judgment: Based on the results of memory tests (such as the Three-Domain Cognitive Assessment Scale) and brain MRI, etc., a final diagnosis is made.
A single blood test cannot be conclusive. It must be combined with other examinations. Follow the specific arrangements of a professional doctor.
6
How many more years can be gained by early detection?
The "golden window of opportunity" for Alzheimers disease is before symptoms appear - at this stage, the brain has lesions but not many nerve cells have died yet. The greatest value of the p-tau217 blood test is that it can "catch" the disease at this stage.
If abnormalities are detected through screening, the progression of the disease can be delayed by adjusting the diet (such as the MIND diet), regular exercise, and memory training.
Patients who meet the criteria can also use the new anti-amyloid protein drugs (such as lecanemab) as early as possible to delay the deterioration of the disease.
Clinical data shows that if brain damage is detected and intervened one year earlier, it can be slowed down by 30%, allowing patients to maintain their self-care ability for an additional 3 to 5 years. For families, this means less care burden and a more dignified life for the elderly.
Dont let "waiting" miss the best opportunity. For Alzheimers disease, "early detection" is ten times more important than "late treatment". The p-tau217 blood test is like a "warning light", allowing us to take action when the disease is just beginning to sprout.
Hainan Chengmei Hospitals Memory Clinic integrates professional resources from multiple fields to provide patients with comprehensive, precise and personalized diagnosis and treatment services.
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Source: WeChat Official Account of Professor Han Yings Team from Xuanwu Hospital