Telephone Interview for Cognitive Status

the National Academy of Sciences Twin Study and the Cache County Study [3] . Unfortunately, even with a fairly high sensitivity and specificity, as suggested by Knopman et al. [1] , many socalled mild or early-onset cases of MCI and dementia would likely be missed by this approach because they would have TICS-m scores above the screening cut point for further evaluation. Thus, the estimation of prevalence in the community would then become a function of the cut point used by the TICS-m for the initial screening and the subsequent diagnostic criteria for dementia and MCI. Variations in this two-step approach for identifying dementia cases in the community account, in part, for the variations in the prevalence of dementia across many populations. Second, the TICS-m can be used in a population study to measure the incidence of dementia over time. However, there is relatively little information to date on the use of the TICS-m to identify incident cases in a longitudinal study. These incident cases are initially likely to be early unless there is a very long time period between examinations. Unless the cut point was set at a very high level, the TICS-m screening may miss many of the early incident cases, similar to the problem in the study of Knopman et al. [1] of discriminating MCI from normal. Recently, in the Ginkgo Evaluation of Memory (GEM) clinical trial, for example, the TICS was used to screen out individuals with a greater likelihood of having dementia, and therefore not being eligible for inclusion into the trial [6] . Such an approach clearly also excludes a certain percentage of individuals who are normal and have scores below the cut point, but this is unlikely to be a problem except perhaps in making it more difficult to recruit in a clinical trial. There is a substantial possibility of bias with regard to the individuals who are screened above and below the cut point for subsequent evaluation for dementia. Most individuals who have dementia will likely progress to substantial disability, at which point the diagnosis of dementia will become obvious to the family, and data to measure dementia cases can be obtained from the family, from medical records, physicians, and social service agencies with little difficulty. The basic problem is that incident dementia cases may die or develop other serious morbidities which mask the specific dementia diagnosis before they are identified using a screening instrument such as the TICS-m. Thus, the early diagnosed dementia cases may die before they are diagnosed as dementia and, therefore, classified based on their last examination before death as being ‘normal’. Consequently, in a longitudinal study of selected risk factors and subsequent incidence of dementia, the risk factors which correlate with both the incidence of dementia and the likelihood of mortality or substantial morbidity and disability will be underestimated in the database. In a randomized clinical trial, this survival bias prior to diagnosis could be of smaller effect since it theoretically should apply to both the cases in the ‘treatment’ arm and the controls. UnforThe paper ‘Validation of the Telephone Interview for Cognitive Status-modified in Subjects with Normal Cognition, Mild Cognitive Impairment, or Dementia’ from the Mayo Clinic provides a valuable contribution to the evaluation of the Telephone Interview for Cognitive Status-modified (TICS-m) in the identification of mild cognitive impairment (MCI) and dementia [1] . The results strongly suggest that the use of TICS-m is of limited value to ascertain differences between Alzheimer’s disease (AD), MCI and normal, at least in older individuals with a very high prevalence of AD and MCI, but is probably somewhat better in separating dementia and MCI from normal. The determination of cognitive status in large populations is a major task, and telephone interviews have been proposed as a low-cost alternative to in-person evaluations. They have shown high sensitivity in cohorts with clearly defined dementia [2, 3] , but they have had difficulty identifying subjects with MCI and early dementia [4] . The Alzheimer’s Disease Cooperative Study found that the TICS-m positive predictive value was 50.9% in a population of 2,431 subjects screened positive for amnestic MCI [4] . Similarly, the Prevention of Alzheimer’s in Society’s Elderly found that half of the subjects who had TICS-m scores in the MCI/ early dementia range had the diagnosis of MCI after a clinic evaluation [5] . Therefore, a critical question posed by this paper and similar studies is: what is the utility of the TICS-m in current research related to dementia (especially in its early stages) and MCI? There are two important aspects that are relevant to the determination of cognitive status using telephone interviews. First, the TICS-m may be useful as an initial screening in studies to determine the prevalence of dementia or MCI in a community. At younger ages ( ! 75 years) for example, the prevalence of dementia is relatively low, and therefore a very large sample size is necessary in order to estimate prevalence with reasonable confidence limits. The telephone screening to identify high-risk individuals who could then be further evaluated in order to estimate dementia may be the most cost-effective approach. Nevertheless, the actual determination of the clinical syndrome (i.e. dementia) is based on the secondary clinical evaluation as was originally performed by Published online: December 10, 2009