TAU PROTEIN IN CEREBROSPINAL-FLUID AS AN AID IN THE DIAGNOSIS OF ALZHEIMERS-DISEASE

Neurofibrillary tangles and dystrophic neurites are characteristic pat hological features found in the brains of Alzheimer's disease (AD) pat ients. A major constituent of these lesions is the cytoskeletal protei n tau. This study examined whether the measurement of tau in cerebral spinal fluid (CSF) has value in the diagnosis of AD. Seventy-seven sub jects were enrolled in this prospective study: These included AD (N = 24), Neurological Controls (dementing diseases/ syndromes, N = 26), No rmal Controls (N = 14), and Others (N = 13). CSF was obtained by lumba r puncture, and tau concentrations (pg/mL) were determined using a dua l monoclonal antibody microplate immunoassay. The mean tau value for A D subjects (1,430 +/- 739) was significantly different from Neurologic al Control subjects (790 +/- 579) (p < 0.001) and Normal Control subje cts (816 +/- 355) (p < 0.001). Tau values were elevated in two Neurolo gical Control subjects, one with Binswanger's disease (age 75) and one with depression (age 90). Tau values were also elevated in three Norm al Control subjects; two were subjects with a family history of AD. Ta u concentrations did not correlate significantly with age in AD subjec ts (r = 0.05, p = 0.82) or in Normal Control subjects (r = -0.49, p = 0.08). Tau also did not correlate with severity of cognitive impairmen t in AD subjects (r = -0.03, p = 0.91) or duration of AD symptoms (r = 0.16, p = 0.52). Based on these results and others, CSF levels of tau protein may provide a useful biochemical marker to aid in the clinica l diagnosis of AD.