The History of Medical Coding


The history of medical coding, or diagnostic coding, dates back to seventeenth-century Great Britain with the London Bills of Mortality. Medical coding can be defined as the process of assigning numeric or a combination of numeric and alpha values to all types of medical services. The services include diagnoses, medical procedures, surgery, drugs and other treatments. The practice of medical coding is a continually evolving process, which has led to greater effectiveness and efficiency in the delivery of health care services.


  • In 1893, the International Statistical Institute approved a standardized system for classifying deaths. The list was prepared by a Paris statistician, Jacque Bertillon, and was called the Bertillon Classification. By 1900, 26 countries had implemented the Bertillon Classification. In 1928, a study sponsored by the Health Organization of the League of Nation discussed how the Bertillon Classification could be expanded to include the tracking of diseases.

    In 1949, the World Health Organization (WHO) realized the idea of enacting a system for tracking mortality as well as causes of diseases on a global basis. The Manual of the International Classification of Diseases, Injuries and Causes of Death (ICD) has served as the foundation for the modern practice of medical coding. Starting with the Bertillon Classification, this list is revised every 10 years. The latest revision is ICD-10.


  • Medical coding in the United States is based on three major coding systems, the Current Procedural Terminology (CPT) and Healthcare Common Procedure Coding System (HCPCS) and International Classification of Diseases (ICD). CPT was initially developed by the American Medical Association back in 1966. CPT codes are updated on an annual basis. HCPCS codes have two tiers of coding.

    The first level is based on CPT and has been around almost as long. Level II was introduced in the early 80s. ICD, which was originally designed as a system for gathering and categorizing and processing statistics related to death. Over the years, it has been revised and expanded to track, monitor and analyze diseases. This system is referred to as the International Classification of Diseases, Clinical Modification (ICD-9-CM).

    In recent years, other branches in the medical field have developed coding specific to their medical expertise. The International Classification of Functioning, Disability and Health (ICF) relates to disabilities. The Diagnosis Related Groups (DRG) is an effort to gain uniformity in the area of diagnostics. The Code on Dental Procedures and Nomenclature (CDT) is used by coders in the field of dentistry. Mental health care professionals used the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) for their coding needs. National Drug Codes (NDC) has been instrumental in developing consistency and standardization of prescriptions drugs.


  • Most of the medical coding in the United States is centered on ICD-9-CM and HCPCS. Hospitals, doctors, nursing homes, home health providers and other health care practitioners used the ICD-9-CM diagnostic codes. The ICD-9-CM is the uniformed system for gathering information regarding inpatient procedures in hospitals.

    The HCPCS is the coding system that is used for outpatient procedures and doctor services. The HCPCS has two levels of coding. Level I is based on the AMA's CPT system. Level II HCPCS codes are used by medical suppliers, ambulance services or medical equipment vendors.

    Besides providing a uniform system for the classification of all types of medical services, coding is also used to ensure that health services providers are properly paid by the health insurance firms, government agencies and patients for the health care services they provide.


  • Historically, all of our lives have been affected in one way or another by the use of coded medical information. For people who are seeking health insurance coverage, medical coding is used to determine if a person is a "good" risk for health insurance coverage. A mistake in medical coding could result in denial of coverage. When it comes to patient care, coding determines which health care services are reimbursed and how much is paid. If an error is made in the coding diagnosis or treatment, payment could be denied or too much can end up being paid for services.


  • ICD-10 is the medical coding system that is currently used in most developing countries around the world. It has been in use around the world since 1993. The latest ICD revision uses an alphanumeric nomenclature that consists of a three to seven code. In the United States, ICD-10 is only used for mortality reporting. ICD-9-CM is still in place for morbidity reporting and procedure reporting in hospitals and health care settings. The Center for Medicare & Medicaid Services (CMS) has set a target date of October 1, 2013, for full execution of ICD-10-PCS, which is the American version of the new coding.

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