P3‐073: Dissociated A<i>β</i> antibody level in newly diagnosed Alzheimer's disease: A population‐based study

In the growing population of aged individuals who are at risk of developing Alzheimer disease (AD) there is an urgent need for a sensitive, specific and preferably, non-invasive, diagnostic standard. Deposition of Aβ is believed to be centrally involved in the pathogenesis of AD. In our previous study, using a technique for dissociating antibody-antigen complexes, we found significant differences in serum antibodies to Aβ between AD and aged-matched control subjects. In this study, samples were obtained as a part of a population based study of the prevalence of AD in a population of Poland (Lublin district - 2,182,191 inhabitants). Stratified sampling and random selection strategies were combined to obtain a representative population for screening (ages >55). From the screened population, 52 persons were diagnosed with AD (DSM IV and ICD 10 criteria) and the group of healthy, age and gender matched controls was selected. The two groups did not differ with respect to other chronic diseases. Sera collected from AD patients and age-matched controls were examined using the antibody-antigen dissociation methodology previously described (Gustaw et al 2008). The level of antibody against Aβ was detectable both in control and AD before and dissociation of Aβ antigen-antibody complex (ELISA). Sigma Stat 3.0 was the tool of statistical analysis. Mann-Whitney test and Pearson Product Moment Correlation were used to compare and correlate outcome parameters respectively. Significant differences were noticed between AD and control patients before dissociation (median O.D. 0.67 vs 0.47 respectively p< 0.001). After dissociation, however, the level of antibody assessed was greater than before dissociation (median O.D. 1.07 vs 0.7 respectively p< 0.001). Significantly the increase in Aβ auto-antibody levels in AD cases after dissociation was much greater than in controls (median difference 0.4 vs 0.2 p< 0.001).Level of Aβ after dissociation correlated negatively with disease duration and age of AD patient (correlation coefficient: -0.7 and -0,5 p< 0,05). No correlation with age was found in the controls. These findings indicate the dissociated Aβ antibody level to be of diagnostic value in the beginning of the neurodegenerative process in AD.