Background Studies examining the prevalence of physical diseases in a particular population tend to rely either on the categorisation and coding of diseases provided by the International Classification of Diseases, Tenth Edition (ICD-10) or on clinical experience. However, the chapters in ICD-10 are broad and do not distinguish between non-communicable and communicable diseases. Thus, the purpose of this study was to develop a framework of non-communicable diseases (NCDs) which could i) be applied to electronic healthcare records and ii) account for multimorbidity.
Methods Three databases were searched on 16 November 2015 via the Ovid research tool: PsycINFO (1806–present), MedLine (1946–present) and Embase (1980–present). The search included the keywords “multimorbidity” OR “multi-morbidity” combined with the keywords “chronic disease” OR “chronic illness”. Studies were included according to the following inclusion criteria: (1) studies which investigated the multimorbidity of chronic conditions in a representative sample; (2) studies that generated a list of chronic conditions based on primary and secondary healthcare data.
Results After applying these criteria, 34 studies were identified as being relevant to the present study and a further 17 studies were identified from references thus providing a total of 51 lists of chronic conditions. The first step in the development of the framework involved collating the 51 lists and ordering the conditions from most to least common. Conditions were included if they appeared in three or more lists. Of the 51 lists, 7 used ICD-10 or ICD-9 codes. Based on these studies, ICD-10 codes were then assigned to each condition. Conditions sharing similar aetiology were identified and grouped together using the 51 lists identified from the literature review and generic health literature. Finally, condition groupings were validated by clinicians who provided suggestions on changes to some of the categories and reported that the framework had good face validity. The final framework included 26 non-communicable physical conditions which fall under ten disease categories.
Conclusion This framework makes a significant contribution to the study of non-communicable physical diseases and may be particularly useful to prevalence studies on multimorbidity which aim to investigate co-occurring physical diseases without the identification of a specific index condition. This coding framework can be directly applied to future studies of NCDs which use electronic healthcare records.