An aberrant protein complex in CSF as a biomarker of Alzheimer disease

Objective: To determine if an aberrant protein complex consisting of prostaglandin-d-synthase (PDS) and transthyretin (TTR) in CSF differentiates between subjects with Alzheimer disease (AD) and normal control (NC) subjects. Methods: Western blot analysis and a unique sandwich ELISA were used to quantify levels of complexed PDS/TTR in ventricular CSF of subjects with autopsy-verified diagnoses and in lumbar CSF of living subjects with mild to moderate probable AD and age-matched NC subjects. Ventricular CSF was obtained from short postmortem interval autopsies of 7 NC subjects (4 men/3 women), 12 diseased control (DC) subjects (7 men/5 women), 4 subjects with mild cognitive impairment (MCI) ( 2 men/2 women), and 8 subjects with late-stage AD (LAD) (4 men/4 women). Lumbar CSF was obtained from 15 subjects with probable AD (5 men/10 women) and 14 age-matched NC subjects (10 men/4 women) and was analyzed in a double-blind fashion. Results: A significant increase in complexed PDS/TTR in ventricular CSF was found in MCI and LAD subjects but not DC subjects compared with NC subjects. Double-blind analysis of complexed PDS/TTR in lumbar CSF showed a significant sixfold increase in levels of the PDS/TTR complex in living probable AD subjects compared with age-matched NC subjects and a 100% sensitivity and 93% specificity in the identification of subjects with AD. Conclusion: After further study of larger numbers of patients, quantifying prostaglandin-dsynthase/transthyretin complex in CSF may be useful in the diagnosis of Alzheimer disease, possibly in the early stages of the disease.