USC researchers have developed a blood test that can identify early signs of Alzheimer’s disease by measuring proteins linked to the condition. The new test, known as Penta-Plex Alzheimer’s Disease Capture Sandwich Immunoassay (5ADCSI), detects five biomarkers simultaneously, which is more than existing blood tests and runs on equipment commonly used in many laboratories. In proof-of-concept study published in the Journal of Alzheimer’s Disease, the researchers selected a series of biomarkers known to build up in Alzheimer’s disease: two types of amyloid (Aβ40 and Aβ42), phosphorylated tau, neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP). They developed a custom test to detect the presence of those biomarkers in a blood sample using the xMAP^® technology. This method uses tiny color-coded beads coated with antibodies that bind to specific biomarkers. When a blood sample is added, the biomarkers in the sample bind to the beads. Powerful imaging sensors then detect the colors emitted from the beads in order to measure the biomarkers. Once the test was built, researchers used it to measure Alzheimer’s-associated biomarkers in 63 blood samples across three groups: 11 patients with Alzheimer’s disease, 17 patients with mild cognitive impairment (a precursor of Alzheimer’s) and 35 healthy participants. The 5ADCSI test detected the highest levels of the biomarkers in patients with Alzheimer’s disease, followed by those with mild cognitive impairment. Researchers then used the same test to measure biomarkers in cerebrospinal fluid (CSF), which typically contains higher levels of Alzheimer’s-associated proteins but is harder and more expensive to collect. They found moderate to strong correlations between blood and CSF results, suggesting the blood test is sensitive enough for early detection of the proteins.