Quest Diagnostics’ AD-Detect Alzheimer’s tests show accuracy in study

Quest’s two AD-Detect blood-based tests, each involving multiple biomarkers, are highly accurate at identifying Alzheimer’s disease pathology in symptomatic patients, supporting diagnosis, according to a new study in Neurology Clinical Practice, a publication of the American Academy of Neurology. The study suggests both tests may fulfill guideline-based criteria for confirming Alzheimer’s disease without follow-up tests, such as amyloid positron emission tomography scan or cerebrospinal fluid tests. The study evaluated two blood-based tests developed by Quest Diagnostics (DGX). One of the tests produces a likelihood score based on results of circulating blood levels of the biomarkers amyloid beta 42/40, phosphorylated tau 217 and ApoE4 proteotype. Quest plans to launch a version of this test in Q1 2026. The study also evaluated a test that includes AB 42/40 and p-tau217 but not ApoE4. The company launched a version of this test in April. Both the Alzheimer’s Association and the Global CEO Initiative on Alzheimer’s Disease recommend that a blood-based test for confirmatory use without follow-up testing have a sensitivity and specificity of approximately 90%. With cutoffs of 91% sensitivity and 91% specificity, the test combining AB 42/40, p-tau217 and ApoE4 blood tests had a positive predictive value of 88% and a negative predictive value of 91% in the intended-use population. In addition, the indeterminate rate was 10% for the test with all three biomarkers and 15% for the test without ApoE4.