CSF β-amyloid 1–42 and tau in Tunisian patients with Alzheimer's disease: The effect of APOE ɛ4 allele

Alzheimer's disease (AD) is the leading cause of dementia. Currently, no definitive diagnostic test for AD exists. An accurate, convenient and objective test to detect AD is urgently needed for efficient drug development and effective clinical use of emerging therapies. The aim of the present work is to investigate the usefulness of cerebrospinal fluid (CSF) β-amyloid protein (Aβ1–42) and total tau protein (t-tau) analyses in the diagnosis of AD and whether apolipoprotein E (ApoE) ɛ4 allele is a factor for AD affecting Tunisian people. Aβ1–42 and t-tau levels were measured in CSF from AD patients (n = 73), non-Alzheimer dementia (nAD, n = 35) and healthy controls (HC, n = 38) by sandwich enzyme-linked immunosorbent assay. Aβ1–42 levels were decreased and t-tau increased in AD patients. The combination of Aβ1–42 and t-tau at baseline yielded a sensitivity of 87.4% for detection of AD. The specificities were 97.3% for controls and 82.7% for other dementia. The ApoE ɛ4 allele frequency (29.5%) was significantly higher in the AD patients than in the nAD patients (17.1%) or in the control groups (9.5%). AD patients carrying ApoE ɛ4 allele had lower Aβ1–42 (p < 0.001) levels than those without a ɛ4 allele. The combination of t-tau and Aβ1–42 is a robust and reliable assay that may be useful in discriminating cases at risk for AD such as ApoE ɛ4 allele carriers from nAD patients or from age-matched control subjects.