A clinical coder – also known as diagnostic coder, medical coder or medical records technician – is a health care professional whose main duties are to analyse clinical statements and assign standard codes using a classification system. The data produced are an integral part of health information management, and are used by local and national governments, private healthcare organizations and international agencies for various purposes, including medical and health services research, epidemiological studies, health resource allocation, case mix management, public health programming, medical billing, and public education.
For example, a clinical coder may use a set of published codes on medical diagnoses and procedures, such as the International Classification of Diseases or the Common Coding System for Healthcare Procedures, for reporting to the health insurance provider of the recipient of the care. The use of standard codes allows insurance providers to map equivalencies across different service providers who may use different terminologies or abbreviations in their written claims forms, and be used to justify reimbursement of fees and expenses. The codes may cover topics related to diagnoses, procedures, pharmaceuticals or topography. The medical notes may also be divided into specialities for example cardiology, gastrointerology, nephrology, neurology or orthopedic care.
A clinical coder therefore requires a good knowledge of medical terminology, clinical documentation, legal aspects of health information, health data standards, classification conventions, and computer- or paper-based data management, usually as obtained through formal education and/or on-the-job training.
Clinical coders in practice 
The basic task of a clinical coder is to classify medical and health care concepts using a standardised classification. Most clinical coders are employed in coding inpatient episodes of care. However, mortality events, outpatient episodes, general practitioner visits and population health studies can all be coded.
Clinical coding has three key phases: a) Abstraction; b) Assignment; and c) Review.
The abstraction phase involves reading the entire record of the health encounter and analysing the information to determine what condition(s) the patient had, what caused it and how it was treated. The information comes from a variety of sources within the medical record, such as clinical notes, laboratory and radiology results, and operation notes.
The assignment phase has two parts: finding the appropriate code(s) from the classification for the abstraction; and entering the code into the system being used to collect the coded data.
Reviewing the code set produced from the assignment phase is very important. Clinical coder must ask themselves, "does this code set fairly represent what happened to this patient in this health encounter at this facility." By doing this, clinical coders are checking that they have covered everything that they must, but not used extraneous codes. For health encounters that are funded through a case mix mechanism, the clinical coder will also review the diagnosis-related group to ensure that it does fairly represent the health encounter.
Competency levels 
Clinical codes may have different competency levels depending on the specific tasks and employment setting:
- Entry-level coder: someone who has completed (or nearly completed) an introductory training course in clinical classification, and whose work is typically checked by an experienced coder before being used.
- Intermediate level coder: has acquired the skills necessary to code many cases independently. Coders at this level are also able to code cases with incomplete information. They have a good understanding of anatomy and physiology along with disease processes. Intermediate level coders have their work audited periodically by an Advanced coder.
- Advanced level coder: authorized to code all cases including the most complex. Advanced coders will usually be credentialled and will have several years experience. An advanced coder is also able to train entry-level coders.
- Nosologist: understands how the classification is underpinned. Nosologists consult nationally and internationally to resolve issues in the classification and are viewed as experts who can not only code, but design and deliver education, assist in the development of the classification and the rules for using it.
In some countries, clinical coders may seek voluntary accreditation through assessments conducted by professional associations or health authorities.
Classification types 
Clinical coders may use many different classifications, which fall into two main groupings: statistical classifications and nomenclatures.
- A statistical classification brings together similar clinical concepts and groups them into one category. This allows the number of categories to be limited so that the classification does not become too big. An example of this is in ICD-10 at code I47.1. The code title (rubric) is Supraventricular tachycardia. However, there are several other clinical concepts that are also classified here. Amongst them are paroxysmal atrial tachycardia, paroxysmal junctional tachycardia, auricular tachycardia and nodal tachycardia.
- In a nomenclature there is a separate listing and code for every clinical concept. So, in the example in the previous paragraph, each of the tachycardia listed would have its own code. This makes nomenclatures unwieldy for compiling health statistics.
Professional associations 
There are several associations that medical coders in the United States may join, including the American Health Information Management Association (AHIMA) and the American Academy of Professional Coders.
Other national associations include the Health Information Management Association of Australia (HIMAA) and the Canadian Health Information Management Association (CHIMA).
See also 
- Clinical medicine
- Health informatics
- Health information management
- Medical classification
- Medical diagnosis
- Marie A. Moisio (2000). A Guide to Health Insurance Billing. Thomson Delmar Learning. ISBN 0-7668-1207-3.
- Michelle A. Green and JoAnn C. Rowell (2011). Understanding Health Insurance, A Guide to Billing and Reimbursement, 10e. Cengage Learning. ISBN 978-1-111-03518-1.
- World Health Organization. Classifying health workers: Medical records and health information technicians. Geneva, 2010.
- Department of Human Services, Victoria, Australia. Clinical Coders Creed. Health Data Standards and Systems Bulletin, Issue 13, 19 July 2000.
- Wooding A (2004). "Clinical coders and decision making". HIM J 33 (3): 79–83. PMID 18490784.
- Walker S (2006). "Capturing health information—a perspectives paper". HIM J 35 (3): 13–22. PMID 18195424.
- Nosologist. Popular Science, posted 11.11.2004.
- Bramley, M; Reid, B. "Evaluation standards for clinical coder training programs" (PDF). Health Information Management Journal 36 (3): 2007.
- AHIMA - Certification and Credentials
- American Academy of Professional Coders
- WHO Family of International Classifications
- American Health Information Management Association
- Canadian Health Information Management Association
- National Library of Medicine (U.S.)