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Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia worldwide. Diagnosis has traditionally relied on a combination of careful clinical assessment, neuropsychological testing, and brain imaging, all of which remain essential in evaluating memory loss and cognitive decline. These approaches help rule out other causes of dementia and establish the clinical suspicion of Alzheimer’s disease.
In recent years, laboratory testing has added a powerful new dimension to the diagnostic process. Biomarker assays provide objective evidence of the biological changes that underlie Alzheimer’s, offering clarity in cases where clinical presentation alone may be uncertain. When used alongside established diagnostic methods, lab tests improve accuracy, enable earlier detection, and help guide treatment decisions.
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia worldwide. Diagnosis has traditionally relied on a combination of careful clinical assessment, neuropsychological testing, and brain imaging, all of which remain essential in evaluating memory loss and cognitive decline. These approaches help rule out other causes of dementia and establish the clinical suspicion of Alzheimer’s disease.
In recent years, laboratory testing has added a powerful new dimension to the diagnostic process. Biomarker assays provide objective evidence of the biological changes that underlie Alzheimer’s, offering clarity in cases where clinical presentation alone may be uncertain. When used alongside established diagnostic methods, lab tests improve accuracy, enable earlier detection, and help guide treatment decisions.
The hallmark pathological features of AD include:
Biomarker testing allows clinicians to measure these processes in living patients. Cerebrospinal fluid (CSF) and blood-based biomarkers provide insight into the presence and progression of disease, improving diagnostic confidence.
Wieslab Diagnostic Services offers a comprehensive panel of biomarker tests that reflect the major pathophysiological changes in Alzheimer’s disease:
Elevated levels of total tau in CSF reflect neuronal injury and degeneration. While not specific to AD, increased tau is an important indicator of ongoing neurodegeneration.
Phosphorylated tau is a highly specific marker for Alzheimer’s pathology. Elevated CSF or plasma pTau181 levels correlate strongly with the presence of neurofibrillary tangles and can help distinguish AD from other neurodegenerative diseases.
The ratio of Aβ42 to Aβ40 is one of the most reliable measures of amyloid pathology. A decreased Aβ42/40 ratio in CSF indicates amyloid plaque deposition in the brain, often occurring years before clinical symptoms appear.
The presence of the APOE ε4 allele is the strongest genetic risk factor for late-onset Alzheimer’s disease. Although not diagnostic on its own, APOE4 testing can provide valuable context when interpreted alongside biomarker and clinical data. The presence of APOE4 is also important for treatments using Leqembi, which is a medicine for treating adults with mild cognitive impairment and early Alzheimer’s disease. It is only used in people with only one or no copy of APOE4.
Neurogranin is a postsynaptic protein associated with synaptic function. Elevated levels in CSF reflect synaptic degeneration, a key feature of AD and a predictor of cognitive decline.
No single biomarker can confirm Alzheimer’s disease in isolation. Instead, diagnostic accuracy is maximized by combining results:
Together, these tests allow clinicians to map the biological processes underlying a patient’s symptoms, supporting early and precise diagnosis.
Laboratory testing has become an essential pillar in the modern diagnostic workup of Alzheimer’s disease. By measuring amyloid pathology, tau pathology, neurodegeneration, and genetic risk, clinicians can achieve a much higher degree of diagnostic certainty than was possible a decade ago. Wieslab Diagnostic Services provides a full suite of biomarker assays—including Tau, pTau, Beta-amyloid 42/40 ratio, APOE4, pTau181, and Neurogranin—empowering clinicians with actionable insights to support patients throughout their diagnostic journey.