Context

The codelist is for use in a neurodegenerative disease burden study (Bristol/ Edinburgh/ Cambridge); and captures prevalent cases with an established diagnosis. The codelists were developed for neurodegenerative diseases of interest: Dementia, Parkinson’s Disease, Parkinson’s-plus syndromes, Motor Neurone Disease. For the diseases of interest, we reviewed established codelists (e.g. QoF for SNOMED terms), and created any required codelists using diagnostic terms as search criteria. ICD-10 browser was consulted for hierarchies and additional terms. For Dementia, we developed codelists for ‘Unspecified Dementia’ and ‘Other Specified Dementia’ which included rarer or less commonly captured causes such as Dementia due to Huntington’s disease.

Inclusion/exclusion criteria

Clinical codes indicative of an established diagnosis were included. For Dementia, we separated codes into three broad groups: Alzheimer’s disease, Vascular Dementia, Other. Other specified dementia: codes where dementia is documented with a specific underlying or associated cause, looking for terms such as ‘due to’, ‘caused by’, ‘associated with’. This list was intended to also capture rare causes of dementia. Unspecified dementia: codes indicating a diagnosis of dementia where no specific cause or subtype is documented.

Borderline cases

Codelist indicating diagnosis "in remission" were accepted, acknowledging that remission of neurodegenerative disease is unlikely (however, symptoms may be controlled). This is because the codelist is developed for prevalence rather than incidence.

Sensitivity vs specificity

The primary aim was specificity. We included codes representing a clinical diagnosis of the condition of interest, rather than codes based solely on symptoms or clinical features.

Additional information

Proposed by W Whiteley & S Sarepalli. Reviewed and modified by A Tamborska & W Shi.