In healthcare, diagnostic codes group and identify diseases, disorders, symptoms and medical signs in order to define morbidities and mortality. In addition, procedural codes identify specific health interventions, surgical procedures, medical tests and results carried out by medical professionals; pharmaceutical codes identify drugs and medications; while other codes can represent patient characteristics such as occupation, social circumstances, ethnicity and religion. These clinical codes provide standardised and highly expressive means for medical professionals to maintain databases of electronic medical records which can be used in observational medical research. There are currently several clinical coding systems used in different countries and regions. For example, Read codes (named after Dr James Read) are the standard clinical coding system used in General Practice in the United Kingdom while the World Health Organisation provides the International Statistical Classification of Diseases and Related Health Problems (ICD).