Chapter6 -HOMI- coding/Classification

Requirements for a classification Scheme

1. Domain Completeness
2. Non-overlapping classes (mutual exclusiveness)
3. Suitability for Purpose
4. Homogeneous ordering - one per level
5. Clear Criteria and boundaries
6. Unambiguous and complete guidelines for application
7. Appropriate level of details

Classification Ordering Principles 

1. Classifications can be ordered by multiple principles 
2. Each ordering throughout a classification = Axis 
3. Multiaxial classifications use multiple axis simultaneously 
4. Example: ICPC = international classification of primary care - classified terms on 2 axis,  the first is organ system which is the  alphanumeric and followed by numeric character 

Thesaurus = list of terms used for an application area or domain 

Thesaurus is always intended to be complete for its domain

Usually includes synonyms and preferred terms

Controlled Vocabulary = A restricted set of preferred terms  used within an organization for a given purpose

Nomenclature - each code is assigned to medical concepts and then these are combined according to specific rules to form complex concepts

What  is the difference between a Classification system and Nomenclature ? 

• A Classification codes are all predefined where as in a Nomenclature, the user is free to combine colds for all aspects involved. 
• Retrieval of information coded with classification system is easy. It is harder for nomenclature because of the complex codes that can be used 

Types of Codes:

1. Number codes - may be sequentional , randmon or researved numbers 
2. Mnemonic Codes - created from characteristics of classes to make for easy memorization
3. Hierarchical Codes - extend codes with additional characters 
4. Juxtaposition codes -composite codes of characters that have a meaning tothe code 
5. Combination codes- ordering combination with combination of digits 
6. Value addition codes - each digit of code is using a power of 2 and sum of digits equals the final code

Taxonomy - theoretical study of classification including basic principles, procedures and rules , comes form Linnaeus's work 

Nosology - science of classification of diseases or more appropriately, the science of classification of diagnostic terms or taxonomy of diagnostic terms

Nosography - science of the description of diseases 

A disease definition gives only the essential characteristics of the disease, where as a description of a disease includes accidental characteristics that is , characteristic that are empirically correlated with the essence of the disease. 

History of Classification 

ICD

1. London bills of Mortality - 1629
2. International List of Causes of Death - 1893, accepted in 1900 - revised by the international statistical Institute up till 1938
3. WHO entrusted to revised list and created an International List of Causes of Morbidity in 1946
4. 6th Revision in France in 1948, 7th revision in 1955, Eighth revision in 1965, Ninth revision in 1975 - Called ICD-9
5. Tenth revision occurred in 1989 - ICD-10,
6. 11th revision in process today 

ICPM = International classification of Procedures in Medicine 

1. First published in 1976, US = CPT, Canada = Canadian Classification Diagnostic m, therapeutic, and Surcial Procedures  (CCD), and France it is called the Catalogue des Actes Medicaux - CDAM

Standard Classified Nomenclature of Disease - used by US btw 1933 an late 1960;s but replaced by an american version of ICD

Classification Problems  - Concerns the ordering of concepts in a way that is logical , sound, elegant, and suited for purpose

Coding problems - technical support that must be provided to enable coding clerks to assign an individual case the right class and produce the right code in an efficient/reliable  way

ICPC  -International Classification of Primary Care -  used to encode encounters structured according to the SOAP  principles 

DSM -Diagnostic and Statistical  Manual Mental Diseases - DSV-IV is compatibility with ICD10. Used by psychiatrists 
DSM - multiaxial classification like ICPC - DSM IV has 5 axis - Clinical Syndromes, Personality disorders, Relevant Physical Disordes, Psychological Stressors, Overall Psychological functioning. DSM V has no axis's for classification - single axis 

SNOMED -

ICD-O - Four digit topology code based on ICD with a morphology code that includes a neoplasm behavior coded and code for histologic grading and differentiation. 

CPT- procedure coding scheme for billing and reimbursement in US

ICPM - International classification of Procedures in MEdicine - informed the procedural coding schemes in ICD9-CM and CCP (canadian procedure ) 

RCC - Read codes - adopted by british health service in 1990's , coves all of health. Merged with Snomed to become SNOMED RT, which then became Snomed CT

ATC - Anatomic Therapeutic Chemical Code - classification of drugs WHO maintains this coding system, Advantages - Defines a drug procuct, active substance, route of administration, and if relevant dose, Both Therapeutically and chemically oriented, Hierarchical for logical grouping, and accepted as standard Internationally for drug utilization research  

ATC - DISADVANTAGES - no dermatological preparations, no locally compounded preparations, no combination products. 

MESH - MEdical Subject Headings - used to code world medical literature. 

DRG = DiagnosisReleated Groups - Basedon ICD9-CM codes and other factors - The grouping of ICD codes is based on factors that affect the cost and treatment, AND length of stay like severity, complications, treatment type ==> resulting classes are homogenous related to cost, but Medically organized.