Clinical performance of scalable automated p-tau 217 multi-analyte algorithmic blood test with reduced intermediate zone using multiplexed digital immunoassay.

introductionTo address an urgent need for a scalable, accurate blood test for brain amyloid pathology that provides a conclusive result for the greatest number of patients, we developed a multi-analyte algorithmic test combining phosphorylated tau (p-tau) 217 with four other biomarkers.

methodsMultiplexed digital immunoassays measured p-tau 217, amyloid beta 42/40, glial fibrillary acidic protein, and neurofilament light chain in 730 symptomatic individuals (training set) to establish an algorithm with cutoffs, and 1082 symptomatic individuals (validation set) from three independent cohorts to identify brain amyloid pathology.

resultsThe algorithmic in validation gave an area under the curve = 0.92, yielding 90% agreement with amyloid positron emission tomography and cerebrospinal fluid. Positive predictive value was 92% at 55% prevalence. The multi-marker algorithm reduced the intermediate zone ≈ 3-fold from 34.4% to 11.9% versus p-tau 217 alone. Diagnostic performance was similar across subgroups. DISCUSSION: The LucentAD Complete multi-analyte blood test demonstrated high clinical validity for brain amyloid pathology detection while substantially reducing inconclusive intermediate results. Highlights: We developed a multi-analyte blood test for assessing brain amyloid status that significantly minimizes the ambiguous "intermediate zone," a key limitation of plasma phosphorylated tau (p-tau) 217 alone.Our test combines plasma levels of p-tau 217, amyloid beta 42/40 ratio, glial fibrillary acidic protein, and neurofilament light chain for a more comprehensive evaluation of amyloid status.We rigorously validated the test's clinical performance in > 1000 samples from symptomatic individuals across three independent cohorts, using cerebrospinal fluid biomarkers and amyloid positron emission tomography as comparators.