A medical classification is used to transform descriptions of medical diagnoses or procedures into standardized statistical code in a process known as clinical coding. Diagnosis classifications list diagnosis codes, which are used to track diseases and other health conditions, inclusive of chronic diseases such as diabetes mellitus and heart disease, and infectious diseases such as norovirus, the flu, and athlete's foot. Procedure classifications list procedure code, which are used to capture interventional data. These diagnosis and procedure codes are used by health care providers, government health programs, private health insurance companies, workers' compensation carriers, software developers, and others for a variety of applications in medicine, public health and medical informatics, including: statistical analysis of diseases and therapeutic actions reimbursement (e.g., to process claims in medical billing based on diagnosis-related groups) knowledge-based and decision support systems direct surveillance of epidemic or pandemic outbreaks There are country specific standards and international classification systems. Classification types Many different medical classifications exist, though they occur into two main groupings: Statistical classifications and Nomenclatures. A statistical classification brings together similar clinical concepts and groups them into categories. The number of categories is limited so that the classification does not become too big. An example of this is used by the International Statistical Classification of Diseases and Related Health Problems (known as ICD). ICD-10 groups diseases of the circulatory system into one "chapter," known as Chapter , covering codes I00–I99. One of the codes in this chapter (I47.1) has the code title (rubric) Supraventricular tachycardia. However, there are several other clinical concepts that are also classified here. Among them are paroxysmal atrial tachycardia, paroxysmal junctional tachycardia, auricular tachycardia and nodal tachycardia. Another feature of statistical classifications is the provision of residual categories for "other" and "unspecified" conditions that do not have a specific category in the particular classification. In a nomenclature there is a separate listing and code for every clinical concept. So, in the previous example, each of the tachycardia listed would have its own code. This makes nomenclatures unwieldy for compiling health statistics. Types of coding systems specific to health care include: Diagnostic codes Are used to determine diseases, disorders, and symptoms Can be used to measure morbidity and mortality Examples: ICD-9-CM, ICD-10, ICD-11 Procedural codes They are numbers or alphanumeric codes used to identify specific health interventions taken by medical professionals. Examples: CPT, HCPCS, ICPM, ICHI Pharmaceutical codes Are used to identify medications