Validity of Dementia Diagnoses in the Danish Hospital Registers

Memory Disorders Research Group, Department of Neurology, The Centre of Neuroscience, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark.
Dementia and Geriatric Cognitive Disorders (Impact Factor: 2.81). 02/2007; 24(3):220-8. DOI: 10.1159/000107084
Source: PubMed

ABSTRACT The validity of dementia diagnoses in the Danish nationwide hospital registers was evaluated to determine the value of these registers in epidemiological research about dementia.
Two hundred patients were randomly selected from 4,682 patients registered for the first time with a dementia diagnosis in the last 6 months of 2003. The patients' medical journals were reviewed to evaluate if they fulfilled ICD-10 and/or DSM-IV criteria for dementia and specific dementia subtypes. The patients who were still alive in 2006 were invited to an interview.
One hundred and ninety-seven journals were available for review and 51 patients were interviewed. A registered diagnosis of dementia was found to be correct in 169 (85.8%) cases. Regarding dementia subtypes, the degree of agreement between the registers and the results of the validating process was low with a kappa of 0.36 (95% CI 0.24-0.48).
The validity of dementia syndrome in the Danish hospital registers was high and allows for epidemiological studies about dementia. Alzheimer's disease, although underregistered, also had a good validity once the diagnosis was registered. In general, other ICD-10 dementia subtypes in the registers had a low validity and are less suitable for epidemiological research.

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    • "Several Danish studies have estimated the PPV of selected diagnoses included in the Charlson comorbidity index (e.g. acute myocardial infarction [27], cerebrovascular disease [28,29], dementia [30], rheumatoid arthritis [31], liver cirrhosis [32], diabetes mellitus [25], cancer [33], haematological malignancies [34] and HIV [35]) in the NRP and generally report of lower PPV's than in our study. These studies validated diagnoses using strict diagnostic criteria, requiring for example specific clinical investigations. "
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    • "First, the validity of the ICD-10 diagnosis of dementia in the DNHR and the DPCR has been found to be high with a correct register diagnosis in 85.8% of cases compared with research-based diagnoses (Phung et al. 2007). The ICD-10 subtype diagnosis of dementia was rather low, but AD, although under registered, also had a good validity once the diagnosis was registered. "
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