Medical Records Coding – An Overview of Coding Schemes

When doctors write reports on diagnoses, treatments, lab results, medications, and so on they write them in simple medical and descriptive terms. After these reports and records are written however, the conclusions need to be put in a form that can be easily interpreted for billing purposes, mainly by insurance companies. This is where medical records coding comes in. It is a system of alpha numeric codes used either nationally or internationally in the health profession to designate various aspects of the medical process. Medical coders are specialists who are familiar with all these codes and the way they fit together on medical records – and whose job it is to come up with an intelligible report that doesn’t have errors and that, more importantly, won’t be rejected by insurance companies.

There are a number of different classification systems which cover 4 basic categories – diagnosis (which also includes morbidity classification, procedures, medications (pharmaceutical classifications), and anatomy (known as topological classification). The following are a few of the most common classification schemes used in the field.

Diagnostic and Procedural Codes


One of the most widely used coding systems is the International Statistical Classification of Diseases and Related Health Problems (usually abbreviated IDC) which is published by the world health organization. This system began in 1893 when a French doctor named Jaques Bertillon introduced a classification system for causes of death at the International Statistical Institute in Chicago. These codes were originally morbidity classifications – doctors and researches needed to be able to compile large volumes of statistical data concerning the causes of death in order to best concentrate their efforts.

The American Public Health Association (APHA) endorsed the system soon after Bertillon introduced it and recommended that several other countries adopt it. They also recommended that the list be updated at 10 year intervals to incorporate new advancements in medicine and disease control. In 1948 the World Health Organization took over the task of publishing the classification system.

Between 1955 and 1983 the coding system was increasingly expanded to corresponded to medical procedures and diagnoses of non fatal diseases and health conditions. It continues to be updated today and is used for both diagnostic and procedural classification. Though the most recent update is IDC-10, IDC-9 remains in wide usage as a morbidity classification system. The adaptation IDC-9-CM (the last two letters standing for clinical modification) is a volume that deals more directly with diagnostics and procedural classification.

CPT and HCPCS codes

This set of codes is published by the American Medical Association and the acronym stands for Current Procedural Technology. Required legally by the Centers for Medicare and Medicaid Services (CMS) and the Health Care Portability and Accountability act of 1996 (HIPAA) this coding system is in wide use. A paid membership in the AMA is required for doctors or patients to have full access to the data.

Often the coding process consists of linking IDC  and CPT codes together in such a way that insurance companies won’t reject claims. Insurance companies would rather not honor a claim if they can find some justification, and inaccuracies or incongruencies between codes in a report may be used by the company to deny its responsibility to pay for medical services. Thus part of the job of a coder is to adjust a claim’s coding so that it is hard for an insurance company to dispute.

The Healthcare Common Procedure Coding System (HCPCS) is an expansion of CPT and is also legally mandated by HIPAA.

Pharmaceutical Codes

Anatomical Therapeutic Chemical Classification System (usually known as ATC). This system is administered by World Health Organization and provides for accurate classification of drugs and medicines. It is broken down into categories based on various systems of the body and the therapeutic effect that a drug will have on that particular category of systems.

Another common pharmaceutical coding system is the National Drug Code or NDC. Mandated by the Drug Listing Act of 1972, all drug manufacturers, processors, or propogators must use this numerical classification to report the substances they are dealing with to the Food and Drug Admintsration.

Topographical Codes

The most widely used anatomical classification system is the Nomina Anatomica, a classification system that originated at the end of the 19th century.. This is not a coding system per se but rather the master reference of anatomical terminology. Though this forms the basis of the anatomical categories used in various coding schemes, usaally what appears on medical records are various anatomical categories or axes that correspond to either diagnoses or procedures.

These are only a few of the systems used in medical coding. Many other coding schemes have also been developed by various organizations for certain purposes and they all must be correlated on medical records in order for them to be clear and easily interpreted. Again, that’s the coder’s job. So if you’re interested in a career in medical records coding you would do well to become very familiar with any and every classification system in current use.

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