Dementia Identification with EMR

The major data sources in the U.K. NHS EMR for identification of dementia cases comprises hospitalisation and death data and dispensed prescribing data. From these sources, we categorise any dementia into the following clinicopathological subtypes: Alzheimer's dementia, vascular dementia, other dementia (any dementia type other than Alzheimer's or vascular), possible dementia, and unspecified dementia (where a specific sub-type is not recorded). For each individual with dementia, the earliest date of occurrence of evidence of dementia in any of the data sources is taken as a surrogate for the incident date of dementia.

For more information about the phenotype, please refer to linked publications.

In the U.K. NHS, Hospitalisation and Death Data are coded using ICD codes from both versions ICD-9 and ICD-10. We use a combination of ICD-10 and BNF codes to adjudicate dementia sub-type as listed in the concept list below.

Given the longitudinal nature of EMR data, we make use of the entire longitudinal data available for each individual to determine a consensus code category from all dementia coding episodes for that individual and apply that category to the date of the first (incident) episode. This is achieved for each individual by determining the total number of distinct dementia coding episodes and for each coding category, calculating its proportion of the total. This proportion is used as a weighting to adjudicate the likely diagnostic category for an individual.

In the U.K. NHS, medications for dementia (donepezil hydrochloride, galantamine, rivastigmine, and memantine hydrochloride) are largely indicated for individuals with Alzheimer dementia; therefore, in the absence of other information, a history of redeeming a prescription for one of these drugs is considered to indicate a diagnosis of Alzheimer or mixed dementia. We use community-dispensed prescribing data available in the EMR to determine the first date of redeeming a prescription in the community for one of these drugs.

For more detail on implementation, please refer to linked publications.