Transcript Document

ICD-10
Shih-jui Lin
Vikrant Deshmukh
Katherine Sward
Outline
 Overview and History
 Content of ICD-10
 Implementation
 Examples
 Modifications
 Evaluation
 Discussion
Requirements of an International
Classification







Comprehensive
Well-defined
Acceptable
Attractive
Reliable
Conservative
Compatible with:
•
•
•
previous classifications
classification of other sectors (e.g. social insurance)
monitoring procedures (e.g. epidemiological reports)
Overview of ICD-10





International Classification of Diseases and
Related Health Problems, the 10th Edition
Maintained by the World Health Organization
Classifies the causes of disease morbidity and
mortality
Contains diseases, symptoms, etiologies, and
injuries
Official Site:
•
http://www.who.int/whosis/icd10/
History of ICD

Origin (1893)

WHO (1946)

Revised every 10 years
• International List of Causes of Death
• International Statistical Institute (ISI)
• Morbidity and mortality
•
ICD-10 (1994)
ICD Revisions
Mortality
ISI
WHO
Mortality
Morbidity
Revision
Implementation in US
1st
1900-1909
2nd
1910-1920
3rd
1921-1929
4th
1930-1938
5th
1939-1948
6th
1949-1957
7th
1958-1967
8th
1968-1978
9th
1979-1998
10th
1999-present
Purpose of ICD-10

WHO:
• Statistically oriented classification system for
•
health census and statistics
To permit the systematic analysis,
interpretation and comparison of mortality and
morbidity data collected in different countries
or areas, at different times
Updates of ICD-10

Must through a local Collaborating Centre
•
•
•

E.g, US: National Center for Health Statistics (NCHS)
Submit to WHO 3 to 6 months before Heads of
Centres annual meeting
Present in Heads of Centres meeting in October
Updates:
•
•
Publish no later than 15 months after each Centre
Heads meeting
Latest update available: 1999
(http://www.who.int/whosis/icd10/corr-eng.htm)
Content of ICD-10



Volume 1:
•
•
•
Tabular List
Cause-of-death titles and codes
Classification at 3- and 4-character levels
Volume 2:
•
•
Instruction Manual
Description, guidelines, and coding rules
Volume 3:
•
•
Alphabetical Index to diseases and nature of injury, external
causes of injury
Table of drugs and chemicals
ICD-10: The Code


Core code:
•
•
•
•
3 character (1 letter + 2 digits)
A00
Up to 2,600 categories
Mandatory for reporting at the international level
Extended code:
•
•
•
•
the 4th digit following a decimal point
A00.0
Up to 26,000 categories
Recommended not required by WHO
ICD-10: The Classification

Two types of classification:
• Main classification
• diagnoses and health status
• E11 = Non-insulin dependent diabetes mellitus
• Supplementary classification
• generally outside the formal diagnoses but related
to health care
• Z83.3 = Family history of diabetes mellitus
ICD-10 Hierarchy for Classification


9,275 codes used in US
•
ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Publications/ICD10/
3 level hierarchy
• Level 1: the 21 chapters
• 21 categories
• Level 2: the 1st – 3rd characters (A00)
• 1643 categories
• Level 3: the 1st – 4th characters (A00.0)
• 7611 categories

Site for browsing the hierarchy and searching diseases:
•
http://www.med-ia.ch/bolinosmed/codifications/icd10/
Example: ICD-10 Hierarchy
Level 1

Level 2
Chap. IV Endocrine, nutritional and metabolic diseases
(E00-E90)
•
Level 3
•
•


E11 = Type 2 diabetes mellitus
•
•
•
•
E11.1 = with ketoacidosis
E11.2 = with renal complications
E11.3 = with ophthalmic complications
…
E12 = Malnutrition-related diabetes mellitus
…
Chap. V Mental and behavioral disorders (F00-F99)
…
The 21 Chapters (1/3)
•
•
•
•
•
•
•
•
•
•
I Certain infectious and parasitic diseases (A00-B99)
II Neoplasms (C00-D48)
III Diseases of the blood and blood-forming organs and certain
disorders involving the immune mechanism (D50-D89)
IV Endocrine, nutritional and metabolic diseases (E00-E90)
V Mental and behavioral disorders (F00-F99)
VI Diseases of the nervous system (G00-G99)
VII Diseases of the eye and adnexa (H00-H59)
VIII Diseases of the ear and mastoid process (H60-H95)
IX Diseases of the circulatory system (I00-I99)
X Diseases of the respiratory system (J00-J99)
The 21 Chapters (2/3)
•
•
•
•
•
•
•
•
XI Diseases of the digestive system (K00-K93)
XII Diseases of the skin and subcutaneous tissue (L00-L99)
XII Diseases of the musculoskeletal system and
connective tissue (M00-M99)
XIV Diseases of the genitourinary system (N00-N99)
XV Pregnancy, childbirth and the puerperium (O00-O99)
XVI Certain conditions originating in the perinatal period
(P00-P96)
XVII Congenital malformations, deformations and
chromosomal abnormalities (Q00-Q99)
XVIII Symptoms, signs and abnormal clinical and
laboratory findings, not elsewhere classified (R00-R99)
•
R42 = Dizziness and giddiness
The 21 Chapters (3/3)
•
•
•

XIX Injury, poisoning and certain other consequences of
external causes (S00-T98)
•
S21 = Open wound of thorax
XX External causes of morbidity and mortality (V01-Y98)
• W54.0 = Bitten by dog
• V47 = Car occupant injured in collision with fixed or
stationary object
XXI Factors influencing health status and contact with health
services (Z00-Z99)
• Z83.3 = Family history of diabetes mellitus
U is not used (reserved for future updates)
Most Important Coding Rules of ICD10
1— Highest Level of Specificity
2— Daggers (†) and asterisks (*) are coded
together, daggers first
3— Principal disease: one disease of major
medical cost
1. Highest Level of Specificity

As specific as possible
• Patient:
• Type 2 diabetes mellitus with renal complications
• Code:
• E11.2 = Type 2 diabetes mellitus with renal
complications
• Not E11 = Type 2 diabetes mellitus
2. Dagger and Asterisk


For a disease encoded by two codes
•
•
Dagger represents etiological aspects.
Asterisk refers to anatomical location
Example:
•
For Renal tuberculosis:
A18.1† urogenital tuberculosis
N29.1* infectious disease of kidney and
ureter classified elsewhere
. .
More on N29

N29 Other disorders of kidney and ureter in
diseases classified elsewhere
•
Code first underlying disease, such as:
•
Excludes: disorders of kidney and ureter in:
• amyloidosis (E85)
• nephrocalcinosis (E83.5)
• schistosomiasis (B65.0-B65.9)
• cystinosis (E72.0)
3. Principal disease

Only one principal disease allowed

The main reason for medical service
If more than one diseases fulfill criteria, choose
the disease with the largest amount of medical
cost

Implementation




Developed by WHO
Modified & distributed in different
countries by the respective health
agencies.
Differences in the implementation
permissible
Reporting must be done strictly in ICD10
Role of WHO





Conduct the process of periodic revisions
Lead the updating between revisions
Develop new methodologies for classifying and
analyzing data
Facilitate training on ICD, its family and its
framework among member countries
Facilitate the improvement of the basic data
Usage in Current Systems

Intended use

Actual use
• Morbidity & Mortality reporting
• Morbidity & Mortality reporting
• Billing & Financial
• Quality Assurance
• Administrative Planning
• Epidemiological & other Research
Licensing & Costs (from WHO)




ICD-10 Volume 1: Tabular List at Sw.fr.
130.-/US $117.00
ICD-10 Volume 2: Instruction Manual at
Sw.fr. 40.-/US $36.00
ICD-10, Volume 3: Alphabetical Index at
Sw.fr. 130.-/US $117.00
WHO retains copyright
Licensing & Costs (U.S.)

Official version can be purchased from WHO
• WHO Publications Center USA
•
•
•
49 Sheridan Avenue
Albany, NY 12210
Same costs at from WHO ($540.00 for the set)
List of causes for mortality data are available from
the NCHS web site
ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/
Publications/ICD10/
Other tabulation lists can be found in Instruction
Manual Part 9 at
www.cdc.gov/nchs/about/major/dvs/im.htm
ICD-10 Languages Available
(WHO editions)
English
Basque
German
Latvian
Slovak
French
Croatian
Greek
Lithuanian
Slovene
Arabic
Czech
Hungarian
Mongolian
Swedish
Chinese
Danish
Icelandic
Norwegian
Thai
Russian
Dutch
Italian
Polish
Turkish
Spanish
Estonian
Japanese
Portuguese
Ukrainian
Armenian
Finnish
Korean
Serbian
Uzbek
http://www.who.int/whosis/icd10/language.htm
Implementation Criteria

Full implementation of ICD-10: A country is considered
as having fully implemented ICD-10 if it is currently used
for:
•
•

Mortality: Causes of death in death certificates are coded
using original ICD-10 codes
Morbidity: Diagnoses in all (or at least in the majority)
hospitals are coded in ICD-10
The fact that a country is reporting to WHO mortality data
coded in ICD-10, and has the ability to produce
tabulations of hospital discharge data by ICD-10 codes,
can serve as a simple criterion or evidence of ICD-10
implementation in a given country
Implementation Criteria


Partial implementation for morbidity:
•
The use of ICD-10 is limited to selected hospitals or
administrative/geographical areas.
Preparatory phase:
•
•
•
A firm decision and action taken by national health
administrations to start preparations for using ICD-10;
Translation of ICD-10 manuals into national language or
other national adaptations, if applicable; acquisition of
sufficient number of copies of ICD-10 manuals and other
related materials;
Adaptation of data registration instruments to ICD-10;
training of coders and other health professionals; pilot
testing in selected health establishments.
ICD-10 Implementation
Time-frames
Country
Australia (ICD-10-AM)
Brazil
Canada (ICD-10-CA)
China
Denmark
France
Germany
Japan
Mexico
Russia
Switzerland
Thailand
UK (England, Whales)
USA
Mortality
1998
1997
2000
2001
1994
2000
1998
1995
1998
1999
1996
1994
2000
1999
Morbidity
1998
1998
2001
2001
1994
1996
2000
1996
1998
1999
1996
1994
1995
2000
http://www.who.int/whosis/icd10/implemen.htm
Summary of ICD-10 implementation
status September 2002
WHO Region (No of
countries/territories)
No of countries
reported full
implementation for
mortality
Full implementation
for mortality &
morbidity
Comments
AFRO (46)
16 (35%)
14 (30%)
Actual level of implementation is likely to be much lower, as the data
for 13 of the countries are from the 2001 survey and without details.
AMRO (49)
46 (93%)
32 (70%)
EMRO (23)
6 (26%)
4 (17%)
Seven countries (30%) reported partial implementation for mortality
and/or morbidity
EURO (51)
42 (82%)
33 (65%)
Four countries will start using ICD-10 for mortality from 1 January
2003, increasing the implementation for mortality up to 90%.
SEARO (10)
8 (80%)
?
Information on mortality coding as per November 2000. No survey in
2002.
WPRO (37)
20 (54%)
16 (43%)
Partial implementation reported for China, Philippines, Viet Nam, i.e.
full implementation expected in coming years. Actual level of
implementation in the Region may be lower, as the data for some
countries are from previous surveys and without details.
Total (216)
138 (64%)
99 (46%)
st
Prokhorskas et al WHO/GPE/CAS/C/02.17
Differences between ICD-10 and
National / Specialist Classification
Automatic conversion from
ICD-10 to ICD-9




Unambiguous mapping:
87%
Mapping based on selection table: 9%
Compromise between preserving
information content & local integrity:2.4%
Impossible to match automatically: 1.6%
Schulz S et al (1998) Meth Inform Med 37:254-9
Automatic conversion from
ICD-9 to ICD-10




Unambiguous mapping:
64%
Codes have been reclassified
Some Codes no longer exist
Others do not have equivalents in ICD10
Schulz S et al (1998) Meth Inform Med 37:254-9
Differences between ICD-9 &
ICD-10 : Breast Cancer













174 malig neo female breast
1740 malig neo nipple
1741 mal neo breast-central
1742 mal neo breast up-inner
1743 mal neo breast low-inner
1744 mal neo breast up-outer
1745 mal neo breast low-outer
1746 mal neo breast-axillary
1748 malign neopl breast nec
1749 malign neopl breast nos
175 malig neo male breast
1750 mal neo male nipple
1759 mal neo male breast nec










C50 malignant neoplasm of
breast
C50.0 nipple and areola
C50.1 central portion of breast
C50.2 upper-inner quadrant of
breast
C50.3 lower-inner quadrant of
breast
C50.4 upper-outer quadrant of
breast
C50.5 lower-outer quadrant of
breast
C50.6 axillary tail of breast
C50.8 overlapping lesion of
breast
C50.9 breast, unspecified
Differences between ICD-9 &
ICD-10 : Cerebral Embolism

434

4340 cerebral thrombosis
43400 cerbral thromb w/o cva
43401 cerbral thromb w/cva





cerebral artery occlusion
4341 cerebral embolism
43410 cerbebral embol w/o cva
43411 cerebral embolsm w/cva









4349 cerebr artery occlus nos
43490 cerbrl art occ w/o infar
43491 cerbrl art occlus w/cva



I63.0 cerebral infarction due to
thrombosis of precerebral arteries
I63.1 cerebral infarction due to
embolism of precerebral arteries
I63.2 cerebral infarction due to
unspecified occlusion or stenosis of
precerebral arteries
I63.3 cerebral infarction due to
thrombosis of cerebral arteries
I63.4 cerebral infarction due to
embolism of cerebral arteries
I63.5 cerebral infarction due to
unspecified occlusion or stenosis of
cerebral arteries
I63.6 cerebral infarction due to
cerebral venous thrombosis,
nonpyogenic
I63.8 other cerebral infarction
I63.9 cerebral infarction,
unspecified
ICD-9 to ICD-10 comparison

Comparability ratio = ICD-10/ICD-9

Cerebrovascular diseases example
•
•
•
The comparability ratio for Cerebrovascular diseases is
1.0588, which indicates a net increase of about 6 percent
in allocation to Cerebrovascular diseases with the
implementation of ICD–10.
Most of the deaths added to Cerebrovascular diseases in
ICD–10 were classified as pneumonia in ICD–9.
This increase is due primarily to the change in Rule 3
(Because pneumonia is a direct consequence of
Cerebrovascular diseases, Cerebrovascular diseases are
selected instead of pneumonia as the underlying cause of
death in ICD–10 when both are listed on the death
certificate)
http://www.cdc.gov/nchs/data/nvsr/nvsr49/nvsr49_02.pdf
Modification of ICD-10



A set of extended codes
•
•
•
Developed by different countries/organizations
Using 5th and 6th digits
Sub-categories under the ICD-10 3-level hierarchy (Level 4)
Codes are
•
•
Consistent in 1st – 4th characters (ICD-10)
Different in 5th – 6th digits (extension)
Examples:
•
•
•
AM: Australian modification
CA: Canadian enhancement
CM: clinical modification
ICD-10 Modification Hierarchy

E00-E90 = Endocrine, nutritional and metabolic diseases
•
•
•


E11 = Type 2 diabetes mellitus
•
•
•
E11.2 = Type 2 diabetes mellitus with renal complications2 diabetes mellitus with
other diabetic renal complication
E11.3 = Type 2 diabetes mellitus with ophthalmic complications
…
E12 = Malnutrition-related diabetes mellitus
…
F00-F99 = Mental and behavioural disorders
…
ICD-10 Modification Hierarchy
WHO Standard
 E00-E90 = Endocrine, nutritional and metabolic diseases
•
E11 = Type 2 diabetes mellitus
•
E11.2 = Type 2 diabetes mellitus with renal complications
•
E11.21
• Type 2 diabetes mellitus with diabetic nephropathy
• Type 2 diabetes mellitus with intercapillary glomerulosclerosis
Modification • Type 2 diabetes mellitus with intracapillary glomerulonephrosis
• Type 2 diabetes mellitus with Kimmelstiel-Wilson disease
• …..
• E11.29
• Type 2 diabetes mellitus with other diabetic renal complication
•
•


•
•
E11.3 = Type 2 diabetes mellitus with ophthalmic complications
…
E12 = Malnutrition-related diabetes mellitus
…
F00-F99 = Mental and behavioural disorders
…
Codes of Modification

Different meaning in different modifications:
•
ICD-10:
•
CM:
•
• E11.2 = Type 2 diabetes mellitus with renal complications
• E11.22 =
•
•
Type 2 diabetes mellitus with Ebstein's disease
Type 2 diabetes mellitus with renal tubular degeneration
AM:
• E11.22 =
•
Type 2 diabetes mellitus with established diabetic
nephropathy
ICD-10-AM





AM = Australian Modification
National Centre for Classification in Health, Australia
Coding Standards in
•
•
Australia
New Zealand
Fourth Edition
•
•
Will be released in February 2004
Will be Implement Ted in July 2004
Official site:
•
http://www2.fhs.usyd.edu.au/ncch/
ICD-10-CA





The Canadian Enhancement
Canadian Institute for Health Information
Standard in Canada
•
•
for morbidity classification
replaces ICD-9 and ICD-9-CM
Started the implementation in 2001
Official site:
•
http://secure.cihi.ca/cihiweb/dispPage.jsp?cw_page=codingclass_icd10_e
ICD-10-CM






Clinical Modification
National Center for Health Statistics (NCHS)
Final draft (Jun. 2003)
2 year implementation
Not yet an anticipated implementation date
Official Site:
•
http://www.cdc.gov/nchs/about/otheract/icd9/abticd10.htm
Purpose of ICD-10-CM



To expand distinctions for ambulatory and
managed care encounters
To include new concepts
•
•
diseases
medical knowledge
To incorporate changes made to ICD-9-CM
since ICD-10 implementation
Purpose of ICD-10-CM

To harmonize with other classification
standards
•
•
ICD-O-2
•
•
•
Used by cancer registry programs since 1995
Chapter 2 (Neoplasms) and morphology codes
correspond to ICD-O-2
http://seer.cancer.gov/tools/conversion/
NANDA
•
•
•
Nursing classification
Harmonization (90-95%) with NANDA
http://www.nanda.org/
Development of ICD-10-CM

Three phases of development
•
•
•

Prototype developed under contract 20 Technical
Advisory Panel members
Enhancements by NCHS, providers & other users
Further enhancements based on public comments
•
•
•
•
Review period: 12/1997 – 02/1998
Draft on the website
Over 1,200 comments
22 organizations/individuals
Final draft (Jun. 2003)
Content of ICD-10-CM (Draft)




23,122 codes
(http://www.ahima.org/dc/NCVHSreport092303.ppt)
5th and 6th digits
More specific diseases, symptoms, injuries and other information
related to health care
Example:
•
•
ICD-10:
•
E11.2 Type 2 diabetes mellitus with renal complications
ICD-10-CM:
•
•
•
E11.21
• with diabetic nephropathy
• with intercapillary glomerulosclerosis
• with intracapillary glomerulonephrosis
• with Kimmelstiel-Wilson disease…
…
E11.29
• with other diabetic renal complication
Summary of ICD-10&CM
ICD-10
ICD-10-CM
Purpose
International standard of
morbidity and mortality
classification
Greater specificity
Extended concepts
Organization
WHO
NCHS, US
Content
21 chapters:
diseases, symptoms,
conditions, etc.
Elaborate subcategories extended
from ICD-10
Code format
E11.2
E11.22x
Size/maximal
9,275 / 26,000
23,122 / 2,600,000
Status in U.S.
Mortality (1999)
Morbidity (2000)
Draft (2003)
not implemented
Evaluation



What ICD is
Desiderata
Other strengths/weaknesses
What ICD-10 is




A classification (arrangement of terms into
groups based on their essential characteristics:
chapters).
A terminology (list of terms within a domain).
A thesaurus: has an alphabetical index.
(And a nomenclature?: very limited, in an
appendix, to specify the morphology of
neoplasms).
Content
+/-
There is a formal process to add content;
significant increase in amount of content
since ICD-9
There is not a formal method for recognizing
and filling in gaps (classifications are
based on importance in public health,
frequency of occurrence…)
Revisions every decade may not capture
rapid growth in medical knowledge
Concept Orientation
+/-
Grouped in a way that was felt to be most
suitable for general epidemiology and health
care evaluation
Inconsistent decisions (theoretical compromises
between classifying based on etiology,
anatomical site, onset circumstances, etc)
Categorizations can be confusing, especially for
lay coders. (Is Gastric Cancer in the GI
diseases or the neoplasms?)
Concept permanence Some terms have been deleted
Some conditions have been
re-categorized (e.g. hemorrhage)
Nonsemantic Identifiers
Codes are hierarchical
Codes are fixed-length alphanumeric
-
Polyhierarchy
-
Most things have only one place in the
hierarchy
There are a few exceptions (the
dagger/asterisk codes)
Formal definitions
-
A small amount of definitions and
synonyms in the appendices
No formal “is_a” relationships
The Infamous NEC and NOS

NEC (“other”):
• when information at hand specifies a condition but
•

no separate code for that condition is provided
E13 = other specified diabetes mellitus
NOS (“unspecified”):
• when information at hand does not permit either a
more specific or “other” code assignment


• E14= unspecified diabetes mellitus
Subcategories .8 (“other xxx”) and .9 (“xxx
unspecified”) are not consistent throughout
“Practically never occurs that a disease cannot
be assigned an ICD code.”
Multiple Granularities +
Three character codes mandatory level
Four character code optional but
recommended
Different countries have different need for
detail
ICD-10-CM goes to a 5th character for
more detail
(U.S. coding rules say
use the longest code available)
Multiple consistent views +/Single hierarchy, can expand (4-5 digit
code) or collapse (3 digit code)
Users may adapt to some extent,
encouraged to coordinate adaptations
through WHO
Representing Context
-
The only relationships are within the strict
hierarchy (no “grammar” and no defined
relationships between concepts)
Little if any context (“how it will be used”)
A few diseases have alternate codes
Intent is not to combine concepts to create new
codes
Graceful Evolution
-
Code changes, re-use of codes, change
categories
You need to know which version of ICD
you’re using to determine the meaning
of a code
Recognizing Redundancy
Most conditions appear only one
place in the hierarchy
+
Except for the dagger/asterisk
conditions!
-
General Weakness

ICD is a classification. 4-digit
categories usually represent sets of
diseases rather than single diseases

No official ICD definitions for the
meanings of categories: the ‘semantic
content’ of a category can only be
estimated
Estimating ‘Semantic Content’


1—the name of the category (e.g. J67
Hypersensitivity pneumonitis due to
organic dust)
2—officially listed inclusions and
exclusions (e.g. K14.0 glossitis
Excludes K14.4 atrophic glossitis)
Estimating ‘Semantic Content’

3—The place of the entry in the structure of the
system (e.g. D02.2 and D14.3 both are bronchus
and lung. However, D02.2 falls under D02 which
is carcinoma in situ of the respiratory system and
middle ear and D14.3 belongs to D14 which is
benign neoplasm of the respiratory system and
middle ear.)
Weaknesses
Requires human coders (often nonMDs
 Code ‘probable’ diseases as
established diagnosis
 Requires large code book and
instruction manual if software is not
available

Weaknesses Continued




Inter-rater reliability questionable
For diseases surveillance, ICD revisions
may create erroneous spikes or valleys
NEC and NOS used quite often
Not enough codes (categories too broad)?
Issues - practical




Changes not updated on WHO website
for dissemination
Not all countries aware of updates to
rules, terms and classes
Countries using different versions of
ICD-10 - problems particularly for
mortality
Opportunities for electronic distribution
Source: Proceedings of ICD10 Update Reference Committee
Issues - clinical





Some areas in urgent need of major
clinical revision, e.g. diabetes
Some areas being revised by WHO
outside URC process (Mental Health)
Compatibility with FIC (ICD-O, ICF, ICE-CI)
Changes from clinical modifications
Need for a procedure classification
Source: Proceedings of ICD10 Update Reference Committee
Strengths


Ubiquitous
"the most common disease classification
system in routine use"


(Schulz et al., 1998, p. 254)
International usage; collaboration
between multiple countries,
organizations, agencies. Revisions by
international collaborative group.
Strengths



Works well for its intended purpose (population
statistics, mortality comparisons, statistical
study of disease phenomena)
Less effective but still sometimes useful for
other purposes (lists of diagnoses, reason for
admission, reason for consultation) IF these
codes will be used as statistical aggregates
Insufficient detail for some purposes (clinical
decision making)
Requirements of an International
Classification







Comprehensive
Well-defined
Acceptable
Attractive
Reliable
Conservative
Compatible with:
•
•
•
previous classifications
classification of other sectors (e.g. social insurance)
monitoring procedures (e.g. epidemiological reports)
References





Chute CG, Cohn SP, Campbell KE, Oliver DE, Campbell JR.
The content coverage of clinical classifications. For The
Computer-Based Patient Record Institute's Work Group on
Codes &Structures. J Am Med Inform Assoc. 1996 MayJun;3(3):224-33.
deKeizer, N.F., Abu-Hanna, A., Zwetsloot-Schonk, J.H.M..
Understanding terminological systems I: Terminology &
Typology. Methods of Information in Medicine. 2000. 39, 16-21.
Gersenovic M., The ICD Family of Classifications Meth Inform
Med 1995; 34:172-5
ICD-10 vol. 1,2,3 World Health Organization Geneva,
Switzerland. 1992
Schulz S, Zaiss A, Brunner R, Spinner D, Klar R. Conversion
Problems concerning Automated Mapping from ICD-10 to ICD9. Meth Inform Med 1998; 37:254-9
References

World Health Organization (WHO)
http://www.who.int

WHO statistical information
http://www.who.int/whosis/icd10/

Centers for Disease Control (CDC) National
Center for Health Statistics (NCHS)


http://www.cdc.gov/nchs
http://www.cdc.gov/nchs/about/otheract/icd9/abticd10.htm
http://www.cdc.gov/nchs/about/major/dvs/icd10des.htm

http://www.cms.hhs.gov/medlearn/icd9code.asp
