Abnormal erythrocyte anion exchange in Alzheimer disease

Context.-Several abnormalities have been described in red blood cells of pa tients with Alzheimer disease (AD), but to date none of these has been conf irmed by a second, independent study. Erythrocyte anion exchange has been r eported to be abnormal in AD; we have developed a new technique for measuri ng anion exchange. Objectives.-To confirm the abnormality of erythrocyte anion exchange in AD and to determine whether the phenomenon has potential for clinical utility. Design.-Comparison of patients with probable AD to age-matched controls. Se tting.-University hospital and ambulatory clinic. Methods.-Chloride-bicarbonate exchange was measured in erythrocyte ghosts r esealed with a fluorescent probe of chloride concentration. Results.-Erythrocyte anion exchange is abnormal in AD. This difference appe ars in titrate but not EDTA anticoagulant. Mahalanobis's generalized distan ce between the 2 populations is 1.7, and a discriminant function derived fr om our technique classifies 82% of the study population in accordance with the National Institute of Neurological and Communicative Disorders and Stro ke-Alzheimer's Disease and Related Disorders Association criteria. Receiver operating characteristic analysis demonstrates the possibility of choosing cutoffs with high sensitivity and specificity. Conclusions. Measurement of red blood cell anion exchange may be useful in classifying patients with AD. The dependence of this phenomenon on anticoag ulant suggests the involvement of platelet activation or complement fixatio n.