COMBINATION ASSAY OF CSF-TAU, A-BETA-1-40 AND A-BETA-1-42(43) AS A BIOCHEMICAL MARKER OF ALZHEIMERS-DISEASE

Cerebrospinal fluid samples from a total of 157 subjects consisting of 55 patients with sporadic Alzheimer's disease (AD), 34 normal control s, 23 patients with non-AD dementia, and 45 with other neurological di seases were examined by ELISA of tau, A beta 1-40, and A beta 1-42(43) . The AD group had a significantly higher level of tau than the normal control group (P<0.001), and the diagnostic sensitivity was 31% and s pecificity was 94%. CSF A beta 1-40 levels did not show any significan t differences. Although the level of A beta 1-42(43) was decreased sig nificantly in the AD group compared to the control group (P<0.005), th e overlap of A beta 1-42(43) levels among all groups meant that none o f the AD samples exceeded the cut-off value, the mean 2SD of normal co ntrol subjects. Reduction of A beta 1-42(43) levels in AD resulted in a significant increase in the ratio of A beta 1-40 to A beta 1-42(43) (A beta ratio) as an improved marker. The diagnostic sensitivity and s pecificity of A beta ratio were 51% and 82% respectively. The three in dexes, using the tan level and A beta ratio (tau or A beta ratio, devi ation score and tau x A beta ratio), showed better sensitivity (58%, 6 7%, 69%) and specificity (82%, 86%, 88%) than previously reported meth ods. Combination assay for CSF tau, A beta 1-40 and A beta 1-42(43) in CSF is a biological marker of AD and may be useful to biochemically m onitor subjects under treatment. (C) 1998 Elsevier Science B.V. All ri ghts reserved.