Two-thirds of dementia cases occur where research barely reaches
Nas margens de um sistema de saúde historicamente desigual, pesquisadores brasileiros da UFRGS avançam com uma descoberta que pode redefinir o acesso ao diagnóstico precoce do Alzheimer: um exame de sangue capaz de identificar a doença com 90% de precisão. Onde antes havia apenas procedimentos dolorosos e caros — inacessíveis a milhões de brasileiros pobres e distantes dos grandes centros —, surge agora a possibilidade de um diagnóstico simples, realizado em qualquer clínica do país. A ciência, aqui, não apenas responde a uma pergunta médica; ela questiona quem merece ser visto pelo sistema antes que seja tarde demais.
- Dois milhões de brasileiros vivem com Alzheimer, mas o diagnóstico precoce permanece fora do alcance de quem mais precisa — populações de baixa renda e regiões remotas dependem de exames caros e invasivos que poucos conseguem acessar.
- A punção lombar e o PET scan, métodos atuais de detecção, exigem infraestrutura hospitalar sofisticada e custos proibitivos, criando uma barreira invisível entre o diagnóstico e a maioria dos pacientes brasileiros.
- Pesquisadores da UFRGS analisaram biomarcadores no sangue de 59 participantes e identificaram que a tau fosforilada 217 é o marcador mais eficaz, atingindo 90% de precisão — resultado que coloca o Brasil na fronteira internacional da neurociência diagnóstica.
- O exame de sangue ainda é caro para uso rotineiro, mas a tendência histórica de queda nos custos de tecnologias diagnósticas alimenta a expectativa de que ele se torne acessível em poucos anos.
- A equipe criou a Iniciativa Brasileira de Biomarcadores em Doenças Neurodegenerativas e busca aprovação da ANVISA para integrar o teste ao SUS, o que tornaria o diagnóstico precoce uma realidade para milhões de brasileiros sem acesso atual.
Uma equipe da Universidade Federal do Rio Grande do Sul demonstrou que um exame de sangue pode detectar o Alzheimer com cerca de 90% de precisão — uma descoberta com potencial de transformar profundamente o diagnóstico da doença no Brasil. O avanço se apoia na identificação de biomarcadores no sangue, assinaturas moleculares que surgem na corrente sanguínea quando a doença se instala, oferecendo uma alternativa concreta aos métodos atuais.
Hoje, confirmar o Alzheimer exige punção lombar ou PET scan — procedimentos dolorosos, caros e concentrados nos grandes centros urbanos. Esse cenário pesa de forma desproporcional sobre os mais vulneráveis: o Brasil tem cerca de 2 milhões de pessoas com a doença, e dois terços de todos os casos de demência no mundo ocorrem em países em desenvolvimento, onde a pesquisa sobre biomarcadores ainda é escassa.
O estudo analisou amostras de sangue de 59 participantes com diferentes perfis clínicos — comprometimento cognitivo leve, demência por Alzheimer e demência vascular. Entre os biomarcadores avaliados, a tau fosforilada 217 se destacou como o mais eficaz na identificação da doença. O exame é tecnicamente viável em qualquer parte do país, embora ainda seja caro para uso amplo.
Para acelerar a mudança, os pesquisadores criaram a Iniciativa Brasileira de Biomarcadores em Doenças Neurodegenerativas, com financiamento dos ministérios da Saúde e de Ciência e Tecnologia. O próximo passo é conduzir estudos maiores e obter aprovação da ANVISA, com o objetivo de incorporar o teste ao SUS. O momento é favorável: nos Estados Unidos, um exame semelhante já recebeu aprovação regulatória, sinalizando que essa abordagem está deixando os laboratórios para entrar na prática clínica. Para o Brasil, onde as desigualdades em saúde são profundas, um diagnóstico mais simples, indolor e acessível não seria apenas um avanço médico — seria um ato de justiça.
A team at the Federal University of Rio Grande do Sul has demonstrated that a simple blood test can identify Alzheimer's disease with roughly 90% accuracy—a finding that could reshape how the condition is diagnosed across Brazil and beyond. The work centers on blood biomarkers, molecular signatures that appear in the bloodstream when the disease takes hold, offering an alternative to the invasive and expensive procedures that currently dominate clinical practice.
Right now, detecting Alzheimer's requires either a lumbar puncture—a painful procedure that extracts fluid from the spinal cord—or a PET scan, both costly and difficult to access for poor patients or those living far from major medical centers. These barriers matter enormously in a country where roughly 2 million people have Alzheimer's, according to the Brazilian Alzheimer's Association. The researchers point out a troubling paradox: two-thirds of all dementia cases worldwide occur in developing nations, yet most research on blood biomarkers has been conducted in wealthy countries. This geographic imbalance means scientists understand the disease poorly in populations with lower education and income—precisely the groups at highest risk.
The UFRGS team analyzed blood samples from 59 participants: 20 with mild cognitive impairment, 22 with Alzheimer's dementia, and 17 with vascular dementia caused by repeated small strokes in the brain. All underwent clinical evaluation, including detailed interviews and medical history reviews. The researchers measured several biomarkers in both blood and cerebrospinal fluid, including beta-amyloid variants, phosphorylated tau, neurofilament light chain, and glial fibrillary acidic protein. Among these, phosphorylated tau 217 proved most effective at identifying the disease in the control group, whose average age was 70.7 years and was predominantly male.
The blood test itself is feasible and could theoretically be performed anywhere in Brazil. Yet it remains expensive—not yet as affordable as a routine complete blood count. Researchers expect costs will drop significantly as the test becomes more widely used, much as other diagnostic tools have become cheaper over time. To accelerate this path, the team has established the Brazilian Initiative for Biomarkers in Neurodegenerative Diseases, funded jointly by the Health Ministry and the Ministry of Science, Technology and Innovation. The next phase involves larger, more rigorous studies to prove the test's effectiveness and secure approval from Brazil's health regulator, ANVISA. If successful, the blood biomarker test could eventually be offered through the country's public health system, the SUS, making early diagnosis available to millions who currently have no access to it.
The timing aligns with international momentum. A U.S. federal health agency has already approved a similar blood biomarker test, signaling that this approach is moving from research into clinical reality. For Brazil, where healthcare disparities run deep and neurological disease burden is rising, the implications are substantial. A test that costs less, causes no pain, and can be administered in any clinic would not merely improve diagnosis—it would begin to close a gap that has long favored the wealthy and left the vulnerable waiting.
Citas Notables
Up to one-third of individuals clinically diagnosed with Alzheimer's in wealthy memory clinics lack the neuropathological features of the disease at autopsy, highlighting the need for better biomarkers to improve diagnostic precision in living patients— UFRGS researchers
La Conversación del Hearth Otra perspectiva de la historia
Why does it matter that most blood biomarker research has happened in wealthy countries?
Because Alzheimer's doesn't care about borders or income. Two-thirds of dementia cases are in the developing world, but we've been studying the disease mostly in rich populations. That means we don't fully understand how it presents in people with different genetics, different diets, different life experiences. The disease might look different in a 65-year-old in São Paulo than in one in Copenhagen.
The test shows 90% accuracy. Is that good enough to replace the current methods?
It's good, but the real question isn't accuracy—it's access. A lumbar puncture is painful and requires a specialist. A PET scan costs thousands and exists only in major hospitals. A blood test can be done in any clinic, any town. If it's 85% accurate but reaches 2 million people instead of 200,000, that's the win.
Why is phosphorylated tau 217 the best marker they found?
That's still being understood. But essentially, tau is a protein that tangles in Alzheimer's brains. When it's phosphorylated—when it's been chemically modified—it seems to be a cleaner signal of the disease. It showed up reliably in their blood samples in a way the other markers didn't.
How long until this is available through the public health system?
They're being careful. They need ANVISA approval, which requires more studies, more data. Probably years. But the infrastructure is being built now. The government is funding it. The precedent exists in the U.S. It's not a question of if, but when.
What happens to someone who gets diagnosed early with this test?
That's the harder question. Early detection is only useful if there's something to do about it. There are some drugs now that slow progression if caught early enough. But this test opens a door that was locked before. What we do with that door is still being written.