DIAGNOSIS OF ALZHEIMERS-DISEASE IN EPIDEMIOLOGIC STUDIES BY STAGED REVIEW OF CLINICAL-DATA

We explored the inter-rater agreement and validity of diagnoses of Alz heimer's disease (AD) and other dementias made in an epidemiological s tudy. A previously described protocol for cognitive screening and clin ical assessment was applied to a large registry of twins. An expert pa nel then reviewed results from the assessment of 41 subjects whose scr eening results suggested the presence of AD. After review of the infor mation at each of four stages of data collection, we assessed inter-ra ter agreement among the experts as well as their individual agreement with the final consensus diagnosis. We investigated these measures to assess the amount and quality, respectively, of new and diagnostically useful information that was revealed at each stage. A new scheme of w eighted differences among the available diagnostic categories was deve loped for these analyses. As expected, incremental information from su ccessive stages of data collection enabled the panel to increase their diagnostic agreement and rates of ''correct'' diagnoses. Over half of the total information was available, however, after review of only th e initial telephone screening results (stage 1). A brief standardized videotape segment of the mental status and neurologic examinations pro vided substantial additional information. We were able to compare the final consensus diagnoses with autopsy results from seven individuals who had consensus clinical diagnoses of Probable or Possible AD (n = 6 ) or ''demented, questionable etiology'' (n = 1). All these subjects h ad Definite AD.