Cerebrospinal fluid tau protein shows a better discrimination in young old(< 70 years) than in old old patients with Alzheimer's disease compared with controls

Tau protein is consistently reported to be elevated in cerebrospinal fluid (CSF) of patients with Alzheimer's disease (AD). CSF tau alone, however, is not a clinically useful diagnostic marker due to its relatively low diagno stic specificity. Therefore, efforts are under way to combine tau measureme nts with other criteria in order to improve diagnostic applicability. We in vestigated whether age could serve as an useful criterion to increase diagn ostic accuracy. CSF levels of tau were measured in young old (<70 years) an d old old (greater than or equal to 70 years) patients with probable AD, el derly patients with major depression (MD), and age-matched healthy controls (HC). In AD patients, CSF tau levels were significantly elevated compared with MD patients and HC (P < 0.001). Based on a previously established cut- off of 260 pg/ml, the discriminative power was higher in the young old than in the old old subjects. Similarly, receiver operating characteristics ana lysis revealed a statistically significant higher correct classification ra te in the young old. Our findings indicate that the discriminative power of CSF tau is higher in the young than in the old old. We suggest that the ef fect of age should be considered in studies investigating CSF tau as a diag nostic marker for neurodegenerative disorders. (C) 1999 Elsevier Science Ir eland Ltd. All rights reserved.