coding and classification lection 1. basic questions introduction to classification classification...

Coding and ClassificationCoding and Classification

Lection 1

Basic QuestionsBasic Questions

IntroductionIntroduction to to classificationclassification

CClassificationlassification basics basics

Medical Medical Classification Systems Classification Systems

1. 1. IntroductionIntroduction to to classificationclassification

In the In the traditional patient recordtraditional patient record, data are , data are available in available in written format onlywritten format only, mainly as , mainly as free text, but sometimes also as numeric free text, but sometimes also as numeric data, such as laboratory test results.data, such as laboratory test results.

ReconstructingReconstructing the patient history from such the patient history from such a handwritten patient record by a clinician a handwritten patient record by a clinician other than the original author is other than the original author is hindered hindered by by the fact that many medical terms are ill-the fact that many medical terms are ill-defined and are perhaps even ambiguous. defined and are perhaps even ambiguous.


Computers have the potential to Computers have the potential to improveimprove legibility, accessibility, and structure, but legibility, accessibility, and structure, but these these pose heavy demandspose heavy demands on on the the data data collection. collection.

It is posible with development and It is posible with development and application application of an of an electronic patient electronic patient recordrecord (also sometimes called (also sometimes called electronic electronic healtshealts record record - EHR - EHR).).


Advantages Advantages of coding medical dataof coding medical data::

Data reduction Data reduction

Standardized terminology Standardized terminology

Enabling statistical overviews and Enabling statistical overviews and research research

Support of management and planning Support of management and planning

Coupling with decision-support systemsCoupling with decision-support systems

2. C2. Classificationlassification basics basics

CClassificationlassification definftiondefinftion

Purpose and conceptsPurpose and concepts

Ordering PrinciplesOrdering Principles

Nomenclatures and ThesauriNomenclatures and Thesauri

CodesCodes

TaxonomyTaxonomy

NosologyNosology

2.1. C2.1. Classificationlassification definition definition

The term The term classifyingclassifying has two different has two different meanings:meanings:

the process of the process of designing designing a a classificationclassification;;

the the coding coding or or descriptiondescription of an object of an object by using codes or terms that are by using codes or terms that are designators of the concepts in a designators of the concepts in a classification.classification.

2.1. C2.1. Classificationlassification definition definition

WWe e will will use only the first meaning of use only the first meaning of classifyingclassifying::

A classification is an A classification is an ordered system of ordered system of concepts concepts within a domain, with implicit within a domain, with implicit or explicit ordering principles.or explicit ordering principles.

A classification is based on A classification is based on prior prior knowledgeknowledge and forms a key to the and forms a key to the extension of knowledgeextension of knowledge

2.2. 2.2. Purpose and conceptsPurpose and concepts

The The purpose purpose of a of a classification classification isis::

((exampleexample)) to support the generation of to support the generation of health care statistics or to facilitate health care statistics or to facilitate research. research.

Examples are the classification of Examples are the classification of abnormalities of electrocardiograms or abnormalities of electrocardiograms or diagnoses of patients into disease diagnoses of patients into disease classesclasses..


CoConcepts ncepts are ordered according to are ordered according to generic relationsgeneric relations..

Generic relationsGeneric relations are relations of the are relations of the type "A is a kind of B," type "A is a kind of B," ((for example, pneumonia is a kind of lung for example, pneumonia is a kind of lung disease, where pneumonia represents disease, where pneumonia represents the the narrowernarrower concept and lung disease concept and lung disease represents the represents the broader broader conceptconcept))..


Classifications contain concepts within a Classifications contain concepts within a certain certain domaindomain..

The The domaindomain can be defined as: can be defined as:

The set of elements to which a variable The set of elements to which a variable or function is limited.or function is limited.

Any area of interest that might be Any area of interest that might be modeled, e.g., to create an information modeled, e.g., to create an information system.system.


Examples of domains are reason for Examples of domains are reason for encounter, diagnosisencounter, diagnosis, and , and medical medical procedureprocedure..In this respect the In this respect the International International Classification of Diseases, 9th edition Classification of Diseases, 9th edition (ICD-9),(ICD-9), is a classification of is a classification of diagnosesdiagnoses..A classification allows one to compare A classification allows one to compare findings collected in different environments.findings collected in different environments.Classifying is done according to a single Classifying is done according to a single criterion: criterion: ageage; that is, age is used as a ; that is, age is used as a differentiating criterion differentiating criterion

2.3. 2.3. Ordering PrinciplesOrdering Principles

In In classifying diseasesclassifying diseases we deal with the we deal with the following aspects, among others: following aspects, among others: anatomic locationanatomic location,,etiologyetiology,,morphologymorphology, and, anddysfunctiondysfunction..

Each of these aspects can be used for a Each of these aspects can be used for a different ordering. Such an ordering different ordering. Such an ordering throughout a classification is called an throughout a classification is called an axisaxis. .


Multiaxial classificationsMultiaxial classifications use several use several orderings simultaneously.orderings simultaneously.

In the In the International Classification of International Classification of Primary Care (ICPC),Primary Care (ICPC), for instance, the for instance, the diagnoses are classified along two axes, diagnoses are classified along two axes, one for the one for the organ systemorgan system (an alphabetic (an alphabetic character) and one for the character) and one for the componentscomponents..

ICPC has primarily been designed for ICPC has primarily been designed for epidemiological purposes. epidemiological purposes.


One of the problems of uniform One of the problems of uniform registration in health care is the registration in health care is the lack lack of a of a common terminologycommon terminology

A A thesaurusthesaurus is a list of terms used for a is a list of terms used for a certain application area or domain. certain application area or domain. Examples are a list of diagnostic terms or Examples are a list of diagnostic terms or a list of terms for laboratory tests. a list of terms for laboratory tests.

For practical usage, thesauri that also For practical usage, thesauri that also contain a list of contain a list of synonyms synonyms for each for each preferred term have also been developed. preferred term have also been developed.


A restricted set of preferred terms used A restricted set of preferred terms used within an organization for a given purpose within an organization for a given purpose is called a is called a controlled vocabularycontrolled vocabulary..

In a In a nomenclaturenomenclature, codes are assigned , codes are assigned to medical concepts, and medical to medical concepts, and medical concepts can be combined according to concepts can be combined according to specific rules to form more complex specific rules to form more complex concepts. This leads to a concepts. This leads to a large number large number of possible code combinationsof possible code combinations. .


In 1933, the In 1933, the New York Academy of MedicineNew York Academy of Medicine started work on a database of medical terms, started work on a database of medical terms, the the Standard Classified Nomenclature of Standard Classified Nomenclature of DiseasesDiseases..The The American Medical AssociationAmerican Medical Association continued continued this work in 1961, and in 1965 this work in 1961, and in 1965 the the Systematic Systematic Nomenclature of Pathology (SNOP)Nomenclature of Pathology (SNOP) coding coding system was published by the American College system was published by the American College of Pathologists.of Pathologists.SNOPSNOP formed the basis for the development of formed the basis for the development of the the Systematized Nomenclature of Human Systematized Nomenclature of Human and Veterinary Medicine ( SNOMED),and Veterinary Medicine ( SNOMED), which is which is an example of such a nomenclature. an example of such a nomenclature.


The difference between The difference between a a classification classification systemsystem and a and a nomenclature nomenclature is that in the is that in the former possible codes are predefined, whereas former possible codes are predefined, whereas in the latter a user is free to combine codes for in the latter a user is free to combine codes for all aspects involved.all aspects involved.

The The retrievalretrieval of records for patients whose data of records for patients whose data fulfill certain classification codes from a large fulfill certain classification codes from a large database is database is relatively easyrelatively easy; retrieving records ; retrieving records for patients stored by using a nomenclature is for patients stored by using a nomenclature is more difficultmore difficult because of the high degree of because of the high degree of freedom, leading to very complex codes. freedom, leading to very complex codes.


Example of a multilevel classification of medical procedures. The Example of a multilevel classification of medical procedures. The differentiating criteriadifferentiating criteria are indicated between rectangles. The are indicated between rectangles. The

criteria for membershipcriteria for membership in each subclass are not adopted here. in each subclass are not adopted here.

2.4. The 2.4. The CodesCodes

Terminology for Terminology for coding coding means that three basic means that three basic elements are used in the so-called semantic elements are used in the so-called semantic triangle: triangle: (1) object, (2) concept, (1) object, (2) concept, andand (3) term. (3) term.Objects,Objects, also called referents, are particular also called referents, are particular things in reality, and they are concrete (e.g., the things in reality, and they are concrete (e.g., the stomach), as well as abstract (e.g., the mind).stomach), as well as abstract (e.g., the mind).A A conceptconcept is a unit of thought formed by using is a unit of thought formed by using the common properties of a set of objects (e.g., the common properties of a set of objects (e.g., an organ).an organ).A A term term is a designation by a linguistic is a designation by a linguistic expression of a concept or an object in a expression of a concept or an object in a specific language.specific language.

2.4. The 2.4. The CodesCodes

CodingCoding is the process of assigning an is the process of assigning an individual object or case to a class, or individual object or case to a class, or to a set of classes in the case of a to a set of classes in the case of a multiaxial classification.multiaxial classification.

In most classifications, classes are In most classifications, classes are designated bydesignated by codes codes..

Coding is, in fact, interpretation of Coding is, in fact, interpretation of the aspects of an object.the aspects of an object.

2.4. The 2.4. The CodesCodes DDifferent ifferent types of codestypes of codes included: included:

Number codes may be issued Number codes may be issued sequentiallysequentially. . This means that each new class will be given This means that each new class will be given the next unused number. The the next unused number. The advantageadvantage is is that new classes can easily be added. that new classes can easily be added. Numbers could be issued at Numbers could be issued at random random to to avoid any patient-specific information is avoid any patient-specific information is hidden in the code. hidden in the code. Series of numbers can be Series of numbers can be reservedreserved for sets for sets of classes. Issuing this type of number is only of classes. Issuing this type of number is only of use with a fixed set of classes, that is, of use with a fixed set of classes, that is, when no expansion of the set of classes is when no expansion of the set of classes is expected.expected.

2.4. The 2.4. The CodesCodes A A mnemonic codemnemonic code is formed from one or more is formed from one or more

characters of its related class rubric.characters of its related class rubric.Advantages:Advantages: t this helps users to memorize his helps users to memorize codes.codes.Disadvantages:Disadvantages: for classifications with many for classifications with many classes this may lead either to long codes or classes this may lead either to long codes or codes with no resemblance to the class codes with no resemblance to the class rubrics.rubrics.UUsed for limited lists of classessed for limited lists of classes. For . For example, hospital departments are often example, hospital departments are often indicated by a mnemonic code, such as ENT indicated by a mnemonic code, such as ENT for the Department of Ear, Nose, Throat, for the Department of Ear, Nose, Throat, CAR for Cardiology, or OB-GYN for the CAR for Cardiology, or OB-GYN for the Department of Obstetrics and Gynecology.Department of Obstetrics and Gynecology.

2.4. The 2.4. The CodesCodes HierarchicalHierarchical codes are formed by codes are formed by extending an extending an

existing code withexisting code with one or more additional one or more additional characterscharacters for each additional level of detailfor each additional level of detail..A hierarchical code thus bears information on A hierarchical code thus bears information on the level of detail of the related class and on the the level of detail of the related class and on the hierarchical relation with its parent class.hierarchical relation with its parent class.This way of coding bears resemblance to the This way of coding bears resemblance to the structure of structure of hierarchical databaseshierarchical databases..This implies that patient data can be retrieved This implies that patient data can be retrieved by using hierarchical codes at a certain level, by using hierarchical codes at a certain level, even when significant extensions or even when significant extensions or modifications are made at lower levels.modifications are made at lower levels.An example are the codes used in An example are the codes used in ICD-9.ICD-9.

2.4. The 2.4. The CodesCodes JuxtapositionJuxtaposition codes are codes are composite codes consisting composite codes consisting

of segmentsof segments. Each segment provides a characteristic . Each segment provides a characteristic of the associated class.of the associated class. for each additional level of for each additional level of detaildetail..

Application:Application: i in n ICPC ICPC a diagnostic code is formed by a diagnostic code is formed by using a code consisting of one letter of the alphabet using a code consisting of one letter of the alphabet (a mnemonic code), followed by a two-digit number.(a mnemonic code), followed by a two-digit number.

Example:Example: all codes with the character "D" are related all codes with the character "D" are related to the tractus digestivus and all codes starting with an to the tractus digestivus and all codes starting with an "N" describe disorders of the nervous system."N" describe disorders of the nervous system.

In the example of ICPC, two independent In the example of ICPC, two independent characteristics are coded simultaneously, and each characteristics are coded simultaneously, and each characteristic has its own position in the code.characteristic has its own position in the code.

2.4. The 2.4. The CodesCodes MMedical procedures edical procedures can be can be classificlassified with ed with ordering ordering principles: principles: action, equipment, aim,action, equipment, aim, and and anatomical site.anatomical site.

The combination of 100 anatomical sites with 20 different The combination of 100 anatomical sites with 20 different actions, 10 different instruments, and 5 different purposes actions, 10 different instruments, and 5 different purposes results in a classification system with a potential of a results in a classification system with a potential of a 100,000 classes and codes.100,000 classes and codes.

A way to cope with A way to cope with it it is the use of a is the use of a combination code.combination code.

By using a By using a six-digit combination codesix-digit combination code consisting of consisting of four four segmentssegments, with segments dedicated to action (, with segments dedicated to action (22 digits), digits), equipment (equipment (22 digits), aim ( digits), aim (11 digit), and anatomical site ( digit), and anatomical site (11 digit), respectively, a coding clerk has to distinguish only digit), respectively, a coding clerk has to distinguish only 135 codes, with which 100,000 combinations can be 135 codes, with which 100,000 combinations can be generated.generated.

2.4. The 2.4. The CodesCodes In In value addition codesvalue addition codes in general only in general only powers of 2powers of 2 are used as a representation of a data item or class.are used as a representation of a data item or class.

AA several characteristics can be coded. several characteristics can be coded. ButBut only only one numberone number instead of a segment for each instead of a segment for each characteristic is used as a code.characteristic is used as a code.

Example:Example: we code the presence or absence of risk we code the presence or absence of risk factors, such as:factors, such as:

- - 2200 = 1 for smoker/0 for nonsmoker, = 1 for smoker/0 for nonsmoker,

- - 2211 = 2 for overweight/0 for no overweight, = 2 for overweight/0 for no overweight,

- - 2222 = 4 for increased cholesterol/0 for not increased = 4 for increased cholesterol/0 for not increased cholesterol. cholesterol.

By using the codes 1 to 7 we can sum all the three risk By using the codes 1 to 7 we can sum all the three risk factors mentioned above.factors mentioned above.

2.5. The 2.5. The Taxonomy Taxonomy

TaxonomyTaxonomy is the theoretical study of is the theoretical study of classification, including its basic classification, including its basic principles, procedures, and rules.principles, procedures, and rules.

Taxonomy is concerned with Taxonomy is concerned with classifications in general. classifications in general.

The term The term classificationclassification is used for the end is used for the end product of the design process. product of the design process.

2.6. The 2.6. The NosologyNosology

NosologyNosology is usually defined as the science is usually defined as the science of the of the classification of classification of diseasesdiseases..

Nosology is usually distinguished from Nosology is usually distinguished from nosographynosography, which is the science of the , which is the science of the description of diseasesdescription of diseases. .

Difference Difference between between the the definitiondefinition and the and the description of diseasedescription of disease : : AA disease disease definitiondefinition gives only essential characteristics of the gives only essential characteristics of the disease, whereas a disease, whereas a descriptiondescription includes includes accidental characteristicsaccidental characteristics..

3. Medical 3. Medical Classification Classification SystemsSystems

ICD - International Classification of ICD - International Classification of DiseasesDiseases

ICPC - International Classification of ICPC - International Classification of Primary CarePrimary Care

SNOMED - Systematized Nomenclature of SNOMED - Systematized Nomenclature of Human and VeterinaryHuman and Veterinary

DRG - Diagnosis Related GroupsDRG - Diagnosis Related Groups

MeSH - Medical Subject HeadingsMeSH - Medical Subject Headings

ATC - Anatomic Therapeutic Chemical ATC - Anatomic Therapeutic Chemical CodeCode

3.1. 3.1. ICDICDICDICD ((International Classification of DiseasesInternational Classification of Diseases )) is is the archetypal coding system for patient record the archetypal coding system for patient record abstraction.abstraction.

The The first editionfirst edition was published in 1900, and it is was published in 1900, and it is being revised at approximately 10-year being revised at approximately 10-year intervals.intervals.

The The most recent version is ICD-10most recent version is ICD-10, which was , which was published in published in 19921992. .

Most present registration systems, however, are Most present registration systems, however, are still based on still based on ICD-9 ICD-9 or its modification, or its modification, ICD-9-ICD-9-CMCM

3.1. 3.1. ICDICDICD consists of a core classification of ICD consists of a core classification of three-digit codesthree-digit codes, which are the minimum , which are the minimum requirement for reporting mortality requirement for reporting mortality statistics to statistics to WHOWHO..

An optional An optional fourth digitfourth digit provides an provides an additional level of detail.additional level of detail.

At all levels, the numbers At all levels, the numbers 00 to to 7 7 are used are used for further detail, whereas the number for further detail, whereas the number 88 is is reserved for all other cases and the reserved for all other cases and the number number 99 is reserved for unspecified is reserved for unspecified coding.coding.

3.1. 3.1. ICDICDThe basic The basic ICDICD is meant to be used for coding is meant to be used for coding diagnostic termsdiagnostic terms..

ICD-9ICD-9 as well as as well as ICD-10ICD-10 also contain a set of also contain a set of expansions for other families of medical terms. expansions for other families of medical terms.

The disease codes of both ICD-9 and ICD-10 are The disease codes of both ICD-9 and ICD-10 are grouped into grouped into chapterschapters..

Example:Example: for tuberculosis the three-digit codes 010 to for tuberculosis the three-digit codes 010 to 018 are used in ICD-9, and the codes A16 to A19 are 018 are used in ICD-9, and the codes A16 to A19 are used in ICD-10.used in ICD-10.

The The U.S. National Center for Health StatisticsU.S. National Center for Health Statistics published a set of clinical modifications to ICD-9, published a set of clinical modifications to ICD-9, ((ICD-ICD-9-CM9-CM)).. It contains an extra level of detail where needed It contains an extra level of detail where needed and alsoand also includeinclude a volume III on medical procedures. a volume III on medical procedures.

3.1. 3.1. ICDICD

Example of a Four-Digit Code Level in ICD-9 and the Five-Example of a Four-Digit Code Level in ICD-9 and the Five-Digit Code Level as Extended by the ICD-9-CMDigit Code Level as Extended by the ICD-9-CM

3.2. 3.2. ICPCICPC The The World Organization of National Colleges, World Organization of National Colleges, Academies and Academic Associations of General Academies and Academic Associations of General Practitioners/Family Physicians (WONCA)Practitioners/Family Physicians (WONCA) did not did not accept ICD-9, but came up with its own classificationaccept ICD-9, but came up with its own classification - - ICPC - International Classification of Primary Care.ICPC - International Classification of Primary Care.

ICPC is a ICPC is a two-axis systemtwo-axis system.. The The first axisfirst axis, primarily , primarily oriented toward body systems (oriented toward body systems (the tractsthe tracts), is coded by ), is coded by a a letterletter, and the , and the second axissecond axis, the , the componentcomponent, is , is coded by coded by two digitstwo digits. The component axis contains . The component axis contains seven code groupsseven code groups..

Example:Example: the diagnosis pneumonia is coded the diagnosis pneumonia is coded R81 R81 ((R R for respiratory tract and for respiratory tract and 81 81 for the diagnostic for the diagnostic component)component)..

3.2. 3.2. ICPCICPC ICPC is used to encode encounters structured ICPC is used to encode encounters structured according to the according to the SOAPSOAP principle principle::

SS for subjective information, e.g., complaints; for subjective information, e.g., complaints; OO is is for objective information, e.g., test and lab results; for objective information, e.g., test and lab results; AA is for assessment, e.g., diagnosis; and is for assessment, e.g., diagnosis; and PP is for is for plan, e.g., diagnostic tests, treatment, etc.plan, e.g., diagnostic tests, treatment, etc.

An An a a way to organize patient-oriented information is way to organize patient-oriented information is by by disease episodes.disease episodes. ICPC can be used to organize ICPC can be used to organize the registration of a disease episode the registration of a disease episode over timeover time, , from its onset to its resolution. A disease episode from its onset to its resolution. A disease episode may include several encounters. Each problem in may include several encounters. Each problem in an encounter should be coded separately.an encounter should be coded separately.

3.2. 3.2. ICPCICPC

Example of aExample of a The Two-Axial ICPCThe Two-Axial ICPC

3.3. 3.3. SNOMEDSNOMED SNOMED (Systematized Nomenclature of SNOMED (Systematized Nomenclature of Human and Veterinary)Human and Veterinary) was first published was first published in 1975 and was revised in 1979in 1975 and was revised in 1979..

SNOMEDSNOMED is also a multiaxial system. is also a multiaxial system. SNOMED IISNOMED II was a code with was a code with 77 axes, and axes, and SNOMED InternationalSNOMED International has has 1111 axes or axes or modules. Each of these axes forms a modules. Each of these axes forms a complete hierarchical classification complete hierarchical classification systemsystem..

3.3. 3.3. SNOMEDSNOMED A diagnosis in A diagnosis in SNOMEDSNOMED may consist of a may consist of a topographic topographic

codecode, a , a morphology codemorphology code, a , a living organism living organism codecode, and a , and a function codefunction code. When a well-defined . When a well-defined diagnosis for a combination of these four codes diagnosis for a combination of these four codes exists, a dedicated diagnostic code is defined.exists, a dedicated diagnostic code is defined.

For example, the disease code For example, the disease code D-13510 D-13510 (Pneumococcal pneumonia)(Pneumococcal pneumonia) is equivalent to the is equivalent to the combination of:combination of:T-28000T-28000 (topology code for (topology code for Lung, not otherwise Lung, not otherwise specifiedspecified), ), M-40000M-40000 (morphology code for (morphology code for Inflammation, not Inflammation, not otherwise specifiedotherwise specified), and ), and L-25116L-25116 (for (for Streptococcus pneumoniaeStreptococcus pneumoniae) along ) along the living organism axis. the living organism axis.

3.3. 3.3. SNOMEDSNOMED

The 11 Axes of SNOMED InternationalThe 11 Axes of SNOMED International

3.4. 3.4. DRGDRG DRG DRG ((Diagnosis Related GroupsDiagnosis Related Groups )) classification is based on classification is based on ICD-9-CM ICD-9-CM codes and codes and other factors not included in other factors not included in ICD-9ICD-9..

The grouping of ICD codes is based on factors The grouping of ICD codes is based on factors that affect the that affect the cost of treatmentcost of treatment and the and the length length of stay in the hospitalof stay in the hospital, such as , such as severityseverity, , complicationscomplications, and , and type of treatmenttype of treatment..

The resulting classes are homogeneous with The resulting classes are homogeneous with respect to costs and they are medically respect to costs and they are medically recognized.recognized.

DRGsDRGs may thus be used for may thus be used for budgetingbudgeting. .

3.4. 3.4. DRGDRG

DRG ExampleDRG Example

3.5. 3.5. MeSHMeSHThe The Medical Subject Headings (MeSH)Medical Subject Headings (MeSH) classification is developed and maintained by classification is developed and maintained by the the National Library of Medicine (NLM)National Library of Medicine (NLM) in the in the USUSAA..

It is generally used to It is generally used to index the world medical index the world medical literatureliterature..

Within the hierarchy of MeSH, a concept may Within the hierarchy of MeSH, a concept may appear as narrower concepts of more than one appear as narrower concepts of more than one broader concept.broader concept.

EExamplexample:: PPneumonia is listed as a respiratory neumonia is listed as a respiratory tract infection as well as a lung disease.tract infection as well as a lung disease.

3.5. 3.5. MeSHMeSH

MeSH ExampleMeSH Example

3.5. 3.5. MeSHMeSH

MeSH in the PubMed Service search result exampleMeSH in the PubMed Service search result example

3.6. 3.6. ATCATC

Anatomic Therapeutic Chemical Code Anatomic Therapeutic Chemical Code (ATC)(ATC) has been developed for the systematic has been developed for the systematic and hierarchical classification of drugs. and hierarchical classification of drugs.

ATCATC is an acronym for is an acronym for anatomical (A),anatomical (A), the the organ system in the body for which the drug organ system in the body for which the drug is given; is given; therapeutic (T),therapeutic (T), the therapeutic the therapeutic purpose for which the drug is used; and purpose for which the drug is used; and chemical (C),chemical (C), the chemical class to which the chemical class to which the drug belongs.the drug belongs.

3.6. 3.6. ATCATCIn the early 1970s, the In the early 1970s, the Norwegian Medicinal Norwegian Medicinal DepotDepot expanded the existing three-level anatomic expanded the existing three-level anatomic and therapeutic classification system of the and therapeutic classification system of the European Pharmaceutical Market Research European Pharmaceutical Market Research AssociationAssociation and added two chemical levels. and added two chemical levels.

Later, the Later, the WHO Drug Utilization Research WHO Drug Utilization Research GroupGroup accepted the ATC classification as a accepted the ATC classification as a standardstandard. .

Presently, the Presently, the WHO Collaborating Center for WHO Collaborating Center for Drug Statistics MethodologyDrug Statistics Methodology in Oslo is in Oslo is responsible for maintaining the ATC codes. responsible for maintaining the ATC codes.

3.6. 3.6. ATCATCThe The advantages advantages of the ATC are as follows:of the ATC are as follows:

It identifies a drug product, including the active It identifies a drug product, including the active substance, the route of administration, and if substance, the route of administration, and if relevant, the dose; relevant, the dose; It is therapeutically as well as chemically oriented, a It is therapeutically as well as chemically oriented, a feature that most other systems lack; feature that most other systems lack; Its hierarchical structure allows for a logical Its hierarchical structure allows for a logical grouping; grouping; It is accepted as the international WHO standard It is accepted as the international WHO standard for drug utilization research.for drug utilization research.

A A disadvantagedisadvantage is that it does not cover combination is that it does not cover combination products, dermatological preparations, and locally products, dermatological preparations, and locally compounded preparations compounded preparations

3.6. 3.6. ATCATC

Five Levels of the ATC Code Illustrated by the Five Levels of the ATC Code Illustrated by the Code for FurosemideCode for Furosemide

ConclusionConclusionThere are many overlapping classifications not only There are many overlapping classifications not only for the coding of diagnoses but also for the for the coding of diagnoses but also for the classification of medical events. classification of medical events. Although most diagnostic coding systems try to be Although most diagnostic coding systems try to be compatible with the ICD family, ICD itself compatible with the ICD family, ICD itself represents only a limited view and is unable to fulfill represents only a limited view and is unable to fulfill the needs of all users.the needs of all users.Systems such as SNOMED have much more Systems such as SNOMED have much more expressive power than the more rigid systems such expressive power than the more rigid systems such as ICD-9-CM.as ICD-9-CM.Wide acceptance of a coding system is essential Wide acceptance of a coding system is essential for the development of decision-support systems. for the development of decision-support systems. International institutions such as WHO with its International institutions such as WHO with its recognized collaborating centers play an important recognized collaborating centers play an important role in the standardization process role in the standardization process

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