A simple blood test can now detect Alzheimer's with 90 percent accuracy
Por décadas, o diagnóstico do Alzheimer dependeu de métodos invasivos, demorados e frequentemente imprecisos — deixando milhões de pessoas ao redor do mundo sem resposta enquanto a doença avançava em silêncio. Pesquisadores da Universidade de Lund, na Suécia, publicaram em julho de 2024 evidências de que um simples exame de sangue pode identificar a doença com 90% de precisão, igualando procedimentos muito mais complexos. É um daqueles momentos em que a ciência oferece não apenas um novo instrumento, mas uma nova possibilidade de dignidade para quem envelhece com medo do esquecimento.
- Médicos de atenção primária acertam o diagnóstico de Alzheimer em apenas 61% dos casos — uma margem de erro que, para 55 milhões de pessoas com demência no mundo, pode significar anos perdidos sem tratamento.
- O estudo sueco com 1.213 pacientes mostrou que proteínas no sangue detectam placas amiloides com a mesma confiabilidade de uma punção lombar ou de um PET scan, sem a dor, o tempo ou a infraestrutura que esses exames exigem.
- No Brasil, o teste PrecivityAD2 já está disponível desde setembro de 2023, mas custa cerca de R$ 3.600 e não é coberto por planos de saúde nem pelo SUS — transformando um avanço científico em privilégio de poucos.
- A expectativa é que clínicas especializadas adotem o exame primeiro, com a atenção primária seguindo o caminho em um ou dois anos, à medida que diretrizes e treinamentos forem implementados globalmente.
Um exame de sangue capaz de detectar o Alzheimer com 90% de precisão — esse é o resultado publicado em julho de 2024 por pesquisadores da Universidade de Lund, na Suécia, no Journal of the American Medical Association. O estudo acompanhou 1.213 pacientes ao longo de quatro anos e comparou o novo teste com dois métodos consagrados: a punção lombar para análise do líquido cefalorraquidiano e o PET scan cerebral. A concordância foi expressiva em todos os casos.
O contraste com os métodos atuais é revelador. Médicos generalistas acertam o diagnóstico em apenas 61% das vezes; especialistas chegam a 73%. Enquanto isso, cerca de 55 milhões de pessoas vivem com demência no mundo — a maioria com Alzheimer —, muitas delas sem diagnóstico correto por anos. O novo exame identifica a presença de placas amiloides no organismo de forma rápida, indolor e viável em qualquer consultório, sem necessidade de equipamentos sofisticados.
O neurologista Sebastian Palmqvist, um dos autores do estudo, destacou que o teste preenche uma lacuna crítica especialmente na atenção primária, onde a maioria dos pacientes busca ajuda pela primeira vez. O pesquisador sênior Oskar Hansson prevê adoção gradual: clínicas especializadas primeiro, seguidas pela atenção básica após atualização de diretrizes e capacitação profissional — um processo estimado em um a dois anos.
O Brasil saiu na frente nessa corrida. O PrecivityAD2 está disponível no país desde setembro de 2023. O obstáculo, porém, é o preço: aproximadamente R$ 3.600 no setor privado, sem cobertura de planos de saúde ou do SUS. A tecnologia existe e funciona. O desafio agora é garantir que ela chegue a quem mais precisa.
A simple blood test can now detect Alzheimer's disease with 90 percent accuracy—a finding that upends how neurologists have approached diagnosis for decades. Researchers at Lund University in Sweden published their results on July 28, 2024, in the Journal of the American Medical Association, demonstrating that a combination of proteins found in human serum can identify the disease as reliably as far more invasive and time-consuming methods.
For years, doctors have relied on a patchwork of tools to diagnose Alzheimer's: brain imaging to spot tissue degradation, cognitive tests to measure mental decline, and patient reports of symptoms. The approach works, but inconsistently. Primary care physicians correctly identify the disease only 61 percent of the time. Even specialists manage just 73 percent accuracy. The gap matters enormously. Around 55 million people worldwide live with dementia, mostly Alzheimer's, and many go undiagnosed or misdiagnosed for years while the disease progresses unchecked.
The Swedish study enrolled 1,213 patients between February 2020 and January 2024, all of whom were being evaluated for Alzheimer's. About two-thirds had mild or subjective cognitive decline; the remaining third already carried a dementia diagnosis confirmed through clinical and cognitive testing. Most underwent a lumbar puncture to collect cerebrospinal fluid—a procedure that is invasive, uncomfortable, and not practical for routine screening. Others received a PET scan to visualize abnormal protein aggregations in the brain. When researchers compared the blood test results against both methods, the numbers aligned: 90 percent accuracy across the board.
The implications are straightforward but profound. A blood test is less invasive, causes no pain, takes minutes rather than hours, and can be performed in any clinic. It detects the presence or absence of amyloid plaques—clumps of misfolded protein that accumulate in Alzheimer's brains and disrupt normal function. Neurologist Sebastian Palmqvist, one of the study's authors, noted that the test addresses a critical gap in diagnostic tools, especially in primary care settings where most patients first seek help. A commercially available blood test could democratize early detection, allowing more people to receive accurate diagnoses sooner and access treatment before irreversible damage occurs.
In the United States, the test is already in use. Oskar Hansson, the study's senior researcher, predicted it will spread to many countries soon, though implementation will follow a measured timeline. Specialized clinics will adopt it first; primary care training and updated clinical guidelines will take another year or two to roll out.
Brazil is ahead of that curve. The test, marketed as PrecivityAD2, has been available since September 2023. It costs approximately 3,600 Brazilian reais in the private sector—a significant expense that puts it out of reach for most Brazilians, since neither health insurance plans nor the public health system cover it. That gap between availability and accessibility remains the next frontier. The test exists. The question now is whether it will reach the people who need it most.
Notable Quotes
The test addresses a critical gap in diagnostic tools, especially in primary care settings where most patients first seek help— Sebastian Palmqvist, neurologist, Lund University
The test will initially be used mainly in specialized clinics, and may take approximately one to two years for guidelines and training in primary care to be implemented— Oskar Hansson, senior researcher, Lund University
The Hearth Conversation Another angle on the story
Why does a 90 percent accuracy rate matter so much if doctors already have ways to diagnose Alzheimer's?
Because the old ways fail a third of the time, even with specialists. A primary care doctor—the person most patients see first—gets it wrong four times out of ten. That means people live with undiagnosed disease, missing the window for early treatment.
And the blood test changes that how?
It's simple, fast, and accurate. You don't need a specialist to order it or interpret it. A nurse can draw blood in any clinic. That removes the barrier that keeps diagnosis locked in hospitals and specialist offices.
The source mentions it costs 3,600 reais in Brazil. That's not cheap.
It's not. For context, that's roughly a month's minimum wage for many Brazilians. So yes, the test exists in Brazil, but only for people who can afford private care. The public system doesn't cover it.
So availability and access are two different things.
Exactly. The test is here. But it's not yet for everyone.
What happens next?
The researchers expect it will move into primary care clinics within a year or two, once training and guidelines are in place. But that timeline assumes resources and infrastructure that don't exist everywhere. In Brazil, that could take much longer.