ABSTRACT
BACKGROUND AND AIMS: Ascertainment bias (AB) indicates a bias of an evaluation centre in estimating the prevalence/incidence of a disease due to the specific expertise of the centre. The aim of our study was to evaluate classification of different types of dementia in new cases appearing in secondary and tertiary centres, in order to evidence possible occurrence of AB in the various (secondary to tertiary) dementia centres. METHODS: To assess the mechanism of AB, the rates of new cases of the different forms of dementia reported by different centres were compared. The centres involved in the study were 11 hospital-based centres including a tertiary centre, located in the University Department of Clinical Neurology. The tertiary centre is endowed with state-of-the-art diagnostic facilities and its scientific production is prominently focused on dementia with Lewy bodies (DLB) thus suggesting the possible occurrence of a bias. Four main categories of dementia were identified: Alzheimer's disease (AD), DLB, fronto-temporal dementia (FTD), vascular dementia (VaD), with other forms in a category apart. The classification rate of new cases of dementia in the tertiary centre was compared with rates reported by secondary centres and rates of recoding were calculated during a follow-up of 2 years. RESULTS: The study classified 2,042 newly diagnosed cases of dementia in a population of 1,370,000 inhabitants of which 315,000 were older than 65. AD was categorized in 48-52 % of cases, DLB in 25-28 %, FTD in 2-4 % and VaD in 17-28 %. During the 2-year follow-up the diagnosis was re-classified in 40 patients (3 %). The rate of recoding was 5 % in the tertiary centre, 2-8 % in referrals from secondary to tertiary centre, 2-10 % in recodings performed in secondary centres and addressed to tertiary centre. Recoding or percentages of new cases of AD or DLB were not different in the comparison between secondary or between secondary and tertiary centres. FTD and VaD were instead significantly recoded. CONCLUSION: The results of the study suggest that in a homogeneous area, AB is not interfering with diagnosis of AD or DLB.
Subject(s)
Bias , Clinical Competence , Dementia/diagnosis , Dementia/epidemiology , Hospitals/statistics & numerical data , Tertiary Care Centers/statistics & numerical data , Alzheimer Disease/diagnosis , Alzheimer Disease/epidemiology , Dementia/classification , Diagnosis, Differential , Frontotemporal Dementia/diagnosis , Frontotemporal Dementia/epidemiology , Humans , Italy/epidemiology , Lewy Body Disease/diagnosis , Lewy Body Disease/epidemiology , Magnetic Resonance Imaging , Prevalence , Retrospective Studies , Tomography, X-Ray ComputedABSTRACT
Twenty patients (mean age 64 years) with a previous episode of transient global amnesia (TGA) were examined to assess the functioning of objective memory (by using the Randt Memory Test), the metamemory capacities (Sehulster Memory Scale), the residual level of retrograde amnesia (Questionnaire of Remote Events), and the level of depression (Geriatric Depression Scale). Patients with residual retrograde amnesia scored significantly lower than non-amnesic ones on indices of both short-term and long-term memory, and for one of three main metamemory components, namely self-rating of memory functioning through comparison with memory functioning of peers (Set3). Age, time interval from TGA attack and TGA duration did not prove to influence memory and metamemory scores. Retrograde amnesia and depression were rather substantially associated (1/5), and this association was found to negatively influence nearly all memory and metamemory scores. Depression level showed a positive correlation with short-term memory functioning in non-amnesics. The different pattern and strength of the relationships between metamemory components and objective memory dimensions observed in amnesics and non-amnesics indicate that metamemory evaluations are more closely related to memory functioning in amnesics than in non-amnesics.
