Roche and Eli Lilly's 97.9% accurate test follows Fujirebio's FDA approval, expanding early diagnosis access
Alzheimer's disease is a degenerative brain disorder that accounts for two-thirds of dementia patients. Although recent treatments have been successively released, offering hope to patients, it is still too early to be complacent. This is because all of these drugs are effective only in the early stages, and there are still no reliable methods for early diagnosis. Existing diagnostic methods, such as high-cost medical imaging or extracting cerebrospinal fluid, cause significant discomfort to patients, making them difficult to perform easily.
A path has now opened for simple blood tests for Alzheimer's dementia to be conducted at local hospitals. The U.S. Food and Drug Administration (FDA) announced on the 13th (local time) that it had approved the blood test 'Elecsys pTau181,' jointly developed by Swiss pharmaceutical company Roche and U.S. Eli Lilly, as a diagnostic test for Alzheimer's disease that can be used in primary medical institutions.
In a press release on the same day, Roche stated that a clinical trial involving 312 participants showed the test could exclude Alzheimer's disease with 97.9% accuracy. This is not the first time an Alzheimer's blood diagnostic test has received FDA approval. Earlier in May, Japanese biotech company Fujirebio also received FDA approval for an Alzheimer's blood test. Could this mark the beginning of the era of blood tests for dementia?
◇Finding Alzheimer's-causing proteins in blood
The blood tests approved by the FDA this year all diagnose Alzheimer's by detecting specific proteins in the blood. Alzheimer's is known to occur when amyloid-beta and tau proteins abnormally accumulate in the brain.
Amyloid-beta is originally a protein that protects nerve cells, but when it detaches from cells and forms clumps, it causes damage. Tau, which acts as a structural binder maintaining nerve cell integrity, becomes problematic when phosphate groups attach to it, causing it to form tangled clumps that impair cognitive function.
Roche's Elecsys measures pTau181, a specific form of tau protein phosphorylated (p) in plasma, the liquid component of blood. This test quantifies how much tau protein has been modified due to Alzheimer's disease. However, Roche's test does not directly identify Alzheimer's patients. Simply put, it diagnoses cases where cognitive function has declined but not to the extent of Alzheimer's disease.
There are two aspects to diagnostic accuracy. Sensitivity refers to how accurately a test identifies those with the disease, while specificity indicates how accurately it rules out those without it. In this context, Roche's Elecsys diagnoses Alzheimer's with approximately 98% specificity.
Fujirebio's Lumipulse test examines the ratio of phosphorylated tau protein pTau217 and amyloid-beta 1-42 protein in the blood. Theoretically, amyloid-beta protein accumulates in the brains of Alzheimer's patients first, followed by clumps of pTau181 and pTau217.
Lumipulse can diagnose both positive and negative cases of Alzheimer's. In a clinical trial involving 499 participants, 97% of those diagnosed as not having Alzheimer's by the Lumipulse test were later confirmed negative in follow-up diagnostics. For those who tested positive, 92% received the same result in subsequent tests. This means Lumipulse has a sensitivity of 92% and specificity of 97% for Alzheimer's diagnosis.
◇Identifying patients in the diagnostic gray zone
The medical community expects these two blood tests to significantly aid in the early diagnosis of Alzheimer's patients who were previously in the diagnostic gray zone. Elecsys is approved in the U.S. for adults aged 55 and older showing signs or symptoms of cognitive decline. The medical community estimates that over 42% of adults aged 55 and older in the U.S. suffer from dementia. However, 92% of adults with mild cognitive impairment, the stage preceding dementia, may go undiagnosed. Despite this, the lack of simple testing methods means many do not receive appropriate treatment.
Joanne Pike, chairperson of the Alzheimer's Association in the U.S., stated in a press release on the 13th, 'This approval is another significant step toward expanding access to Alzheimer's diagnosis,' adding, 'By using tools to rule out Alzheimer's in primary care settings, we can help identify the causes of cognitive decline more quickly.'
Current Alzheimer's diagnosis involves high-cost positron emission tomography (PET) scans to detect amyloid-beta protein clumps in the brain or direct analysis of cerebrospinal fluid. Blood tests that rule out Alzheimer's can allow appropriate treatment without the need for difficult and expensive procedures. If a blood test indicates Alzheimer's, confirmation via existing methods enables early and appropriate treatment.
The U.S. FDA approved Leqembi, jointly developed by U.S. Biogen and Japan's Eisai, as an Alzheimer's treatment in 2023. The following year, it approved Kisunla, developed by U.S. Eli Lilly, also as an Alzheimer's treatment. Both are antibody therapies that remove amyloid-beta protein clumps accumulated in the brain, targeting early-stage patients, making early diagnosis critically important.
◇Potential reduction in medical costs for developing countries
Alzheimer's blood tests could lead to significant reductions in medical costs. According to the World Health Organization (WHO), there were 57 million dementia patients worldwide as of 2021, a number that could triple by 2050. The economic loss from dementia reached 1.3 trillion dollars (1,851.46 trillion Korean won) in 2019, with 60% of patients in middle- and low-income countries struggling to afford care. If blood tests become widespread, early diagnosis and treatment could reduce these costs.
The scientific community anticipates that a wider variety of Alzheimer's blood tests will advance patient diagnosis and treatment. Ashvini Keshavan, a neurologist and biomarker researcher at University College London (UCL) in the U.K., told the international journal Nature on the 17th, 'An increasing number of companies are developing blood tests to measure Alzheimer's biomarkers,' adding, 'The presence of competition in this field is a positive development.'
Richard Isaacson, M.D., who founded the Alzheimer's Prevention Clinic in the U.S., stated in a CNN interview on the 14th, 'I remain cautiously optimistic about the future of Alzheimer's blood test technology,' adding, 'I firmly believe we are only in the top of the first inning of a nine-inning baseball game.'