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: 3.55). 02/2007; 24(3):220-8. DOI: 10.1159/000107084
Source: PubMed


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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    • "AD was diagnosed according to ICD-10 category F10.2x by senior physicians responsible for the formulation of the individual treatment plan. The ICD-10 coding system has been proven to be largely reliable and valid for definitive diagnoses such as Alzheimer's disease, schizophrenia, or type-2 diabetes mellitus, although errors are found in the coding of non-specific diagnoses such as ''viral infections'' [19] [41] [59]. As the study was naturalistic with high case numbers, no structured interviews were available. "
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    • "Consequently, the final diagnosis at discharge that was registered in the hospital electronic diagnoses database was used. The accuracy of hospital registry data in identifying patients with an ICD-10 diagnosis of dementia has been confirmed in a recent Danish study [43]. Additionally, a clinical diagnosis of AD conforms to the definite pathological diagnosis 70–90% of the time [4]. "

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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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    ABSTRACT: The Charlson comorbidity index is often used to control for confounding in research based on medical databases. There are few studies of the accuracy of the codes obtained from these databases. We examined the positive predictive value (PPV) of the ICD-10 diagnostic coding in the Danish National Registry of Patients (NRP) for the 19 Charlson conditions. Among all hospitalizations in Northern Denmark between 1 January 1998 and 31 December 2007 with a first-listed diagnosis of a Charlson condition in the NRP, we selected 50 hospital contacts for each condition. We reviewed discharge summaries and medical records to verify the NRP diagnoses, and computed the PPV as the proportion of confirmed diagnoses. A total of 950 records were reviewed. The overall PPV for the 19 Charlson conditions was 98.0% (95% CI; 96.9, 98.8). The PPVs ranged from 82.0% (95% CI; 68.6%, 91.4%) for diabetes with diabetic complications to 100% (one-sided 97.5% CI; 92.9%, 100%) for congestive heart failure, peripheral vascular disease, chronic pulmonary disease, mild and severe liver disease, hemiplegia, renal disease, leukaemia, lymphoma, metastatic tumour, and AIDS. The PPV of NRP coding of the Charlson conditions was consistently high.
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