Analytical performance and clinical utility of the INNOTEST® PHOSPHO-TAU(181P) assay for discrimination between Alzheimer's disease and dementia with Lewy bodies

Background: Total tau (T-tau) and β-amyloid(1-42) (Aβ1-42) levels in cerebrospinal fluid (CSF) can differentiate Alzheimer's disease (AD) from normal aging or depressive pseudo-dementia. Differential diagnosis from dementia with Lewy bodies (DLB) in clinical settings is difficult. Methods: The analytical performance of the INNOTEST® PHOSPHO-TAU(181P) assay was validated in terms of selectivity, sensitivity, specificity, precision, robustness, and stability. Clinical utility of the assay alone, or combined with T-tau and Aβ1-42, for discrimination of AD (n=94) from patients suffering from DLB (n=60) or from age-matched control subjects (CS) (n=60) was assessed in a multicenter study. Results: CSF concentrations of tau phosphorylated at threonine 181 (P-tau181P) in AD was significantly higher than in DLB and CS. Discriminant analysis, a classification tree, and logistic regression showed that P-tau181P was the most statistically significant single variable of the three biomarkers for discrimination between AD and DLB. Conclusions: P-tau181P quantification is a robust and reliable assay that may be useful in discriminating AD from DLB. Clin Chem Lab Med 2006;44:1472–80.