The Read clinical classification (Read codes): General description

British Hornceopathic Journal January 1991, Vol. 80, pp. 14-20

The Read clinical classification (Read codes)

General description

JAMES READ

Introduction There are six key criteria which a standard computerized medical language must satisfy. It must be: Comprehensive, Hierarchical, Computerized, Coded, Cross-referenced, Dynamic.

The medical ' term' is the currency of com- munication. Whether in primary, secondary or tertiary medical care, and whether in clinical care, medical teaching, research, health care administration, health care financing or health care planning--medical terms are the primary information carriers.

The enumeration and definition of these medical terms into a standard medical language and nomenclature has become fundamental to the whole of health care computing.

Computers can store, analyze, aggregate, manipulate, retrieve and transfer enormous amounts of data. However, the computer must have the data, the medical 'terms', in the most appropriate format, for optimal performance for input and for output. Because of the absence of one computerized nomenclature to meet on its own all of the needs created, health care pro- viders with computers are customizing pre-existing inappropriate systems, developing their own ad hoc variations and rapidly becoming data- incompatible with others--even in similar countries, in similar fields, .and with similar systems. A need has been created.

The features of the Read Clinical Classifi- cation (Read codes) ~ will be described to illus- trate a solution to this need and also to show how the six key criteria described above may be satisfied.

The Read Clinical Classification (Read codes) Comprehensive The Read codes cover the whole of medicine in the detail needed for patient medical records--

Diseases Occupations History/Symptoms Examinations/Signs Diagnostic procedures Radiology/Diagnostic imaging Preventive procedures Operative procedures Other therapeutic procedures Administration Drugs/Appliances Health status measurement DRGs 2

They can be used in primary, secondary and tertiary care, and by clinicians, technicians, paramedics, researchers, administrators and planners.

We need to identify the medical concepts or 'terms' from all branches of medicine, from different countries and from different cultures in natural language to produce a common 'rneta- language', from which the following can be defined:

�9 'preferred' terms for each concept �9 true 'synonyms' for preferred terms �9 'homonyms' - - terms with differing meanings

in different contexts �9 'deprecated' terms or misnomers

The ordered list of preferred terms is the nomenclature, the infrastructure of medical knowledge.

The Read codes contain, at present, a nomenclature of 100,000 terms and a list of 150,000 synonymous terms. Synonyms are linked to their 'preferred' term by a unique secondary or synonym code. Each term in the nomenclature has a definable load of lexical knowledge--i.e, knowledge 'arcs' link each term to many related terms--and this represents our current knowledge about the term, e.g. myorcardial infarction (Fig. 1).

14

Volume 80, Number 1, January 1991 15

EP1DEMIOLOGY

A E T I O L O ~

OUTCOME

X-RAY

MYOCARDI AL INFARCTION

SYMPTOMS SIGNS

LABORATORY

EATMENT

COMPLICATIONS

Figure 1: Myocardial infarction attributes.

Hierarchical The nomenclature has to be organized into 'classes' and classified by attributes, e.g. aetiol- ogy, physiology, anatomy. The attributes selected in each area of the classification should take into account the 'current knowledge' of each term. Multiple attribute selection produces a compound hierarchy.

The hierarchy is produced by partitioning the nomenclature into classes by the selected attribute, separating the classes into sub-classes with stepwise ranking of the concept until 'terminal' terms are reached. Some terminal terms need multiple semantic addresses, or codes, e.g. men- ingococcal meningitis, diabetic retinopathy, clo- nidine. This produces a compound tangled hierarchy that is essential for clinicians in differing domains. Each domain of medicine needs to add missing terms and further divide current terminal terms. The structure of the Read codes have been specifically designed for this expansion and for future updating.

The Read codes are an hierarchial nomenclature that uses alpha-numeric codes:

0 - - 9 A - - Z a - - Z

There are 58 options at each junction in each level.

The letters 'i' and 'o' are excluded to avoid confusion with 1 and 0.

The five levels of code hierarchy give 58 to the power of 5 = 656,356,768 possible codes in the existing framework.

Specified at present are 100,000 preferred terms and 150,000 synonymous terms.

The level of detail increases as the code moves from left to right (Fig. 2). This structure allows for straightforward expansion to incorporate additional terms at each level of the hierarchy

without disturbing the position of the current terms and their codes. This is a fundamental rule of coding. Further levels of hierarchy can be added if more detail is needed.

The hierarchy can be used at any level of detail for clinical, statistical and administrative pur- poses; it allows for the most detailed clinical needs and the most non-specific administrative needs.

For example, a surgeon may need to record: 7702--Emergency excision normal appendix

An administrator/manager will be happy with: 770..--Appendix operations

Government will be happy with: 7. . . .--Operations

'One million more 7s performed under the NHS last year'

Management systems can be 'piggy-backed' onto accurate clinical systems.

Computerized The Read codes have been developed specifically for use with computers, with: �9 5 digit alpha-numeric codes for each term �9 a short fixed-length description of terms with a

30 character limit �9 a medium fixed-length description of terms

with a 60 character limit �9 a long fixed-length description of terms, with a

198 character limit being developed �9 a user interface based on natural language,

due to the extensive use of synonyms �9 semi-automatic encoding from natural lan-

guage to the alpha-numeric code. The user accesses codes by:

�9 natural language--typing the first three or four digits of the term required

�9 typing in the code if it is known from a protocol �9 computerized protocol code allocation �9 accessing the levels of the hierarchy, the

options at each level can be traversed by one key depression to become more detailed, or less detailed. Codes from all levels of hierarchy can be used.

Coded The five character alpha-numeric codes used in the Read codes give a unique identifier to each

Level Term Read ICD-9-CM 3

1 Circulatory system diseases G .... 39~459 2 Ischaemic heart disease G3... 410M.14 3 Acute myocardial infarction G30.. 410 4 Other acute myocardialinfarct G30y. 410.8 5 Acute papillary muscle infarct G30yl 410.8

Figure 2: Example of Read code hierarchy.

16 British Hornceopathic Journal

longer medical term they represent. This is vital for the computer because: �9 it facilitates data-compaction for medical data

storage and for the transfer of that data �9 it avoids the problems of ambiguity and of

homonyms in medical language �9 the ASCII hierarchical order of the codes

facilitates aggregation, analysis, manipulation and retrieval of the data.

Cross-referenced The Read codes are at least as detailed as, and are cross-referenced to (manually and electron- ically) and compatible with, all widely used standard statistical classifications, such as �9 ICD-9 4 �9 ICD-9-CM �9 OPCS-4 5 �9 CPT-4 6 �9 BNF 7

The Read codes are a 'superset' of the above. New work has been done in areas of medicine where there was no standard. Compatibility with existing standards is essential if comparisons are to be made with existing data bases. Internal mapping is present to DRGs and K6rner. 8 Auto- matic grouping of DRGs from clinical data can be produced (Fig. 3).

The Read codes are at least as detailed as all the classifications included in its umbrella. It therefore follows that the Read codes have a precise one to one cross-reference to all terms in the classifications included.

Dynamic A computerized medical language has to be dynamic if it is to be used to make computerized medical records. New medical terms--whether diseases, drugs, occupations, etc.--must be added to the system as soon as they are identi- fied, as must new synonyms and eponyms. As new standards are adopted, e.g. ICD-10, these need to be reflected in the system at once. When new research projects are started, the terms used in them must immediately be available.

In a closed system, the number of terms would be fixed and would remain static. On the other hand, in an open system, the number would be ill-defined and undefined.

The Read codes are a 'quasi-closed' system in which, at any given time, the medical terms are fixed but are periodically and formally updated by a publicly-known system. Updates are regu- larly sent to all users on disk or via modem as specified--xluarterly, monthly or more fre- quently, even daily if required.

A p p l i c a t i o n s o f t h e RCC

Input The Read codes provide a tool with which computerized medical records can be created. Quick, fast, accurate data-entry can be achieved with no typing skills needed and no spelling mis- takes. The data being entered is validated by appearing on the screen. More specific data- entry is possible with further levels of hierarchical detail about the chosen term being displayed if appropriate and if accessed by a synonym the 'preferred' term may be entered.

Output Once the medical record has been computerized in sufficient detail, the benefits of medical computing can be realized: �9 Clinical and management protocols for pre-

ventive, diagnostic, therapeutic and follow-up care of patients

�9 Decision support systems, e.g. Philex drug database, the Oxford System of Medicine and expert systems

�9 Clinical self and peer audit �9 Clinical trials and research �9 Data-transfer of individual and/or aggregate

patient records with data-compression, software, hardware and language are no barrier when using a standard code and rubric format

�9 'Piggy-backing' off the clinical record at any level of detail for the needs of management/ administration, health service planning, epi- demiological surveys and national/international comparisons.

Read rodes

OPCS-4 OPCS P R O C E D U R E S O C C U P 9

ICD-9 I

ICD-9-CM DIAGNOSES

BNF DRUG

TARIFF 1~

DRGs HISTORY/SYMPTOMS EXAMINATION/SIGNS

PREVENTION ADMINISTRATION HEALTH STATUS

Figure 3: Relationship to other classifications.

Volume 80, Number 1, January 1991 17

Output interrogation The Read codes can be interrogated uni-axially through their own structure or through the structure of any of the classifications to which they are cross-referenced.

A multi-axial hierarchical output interrogation table is being developed with the four additional axes of anatomy, structure/form, cause and system. The whole nomenclature or any range of the uni-axial classification options can then be interrogated for any range of any level of any number of the multi-axial output table options.

Implications The adoption of a standard medical nomenclature and classification is the first priority in medical informatics nationally and inter- nationally. The European AIM (Advanced Informatics in Medicine) project recognizes that the continued absence of an accepted standard is inhibiting development at all levels in health care, i.e. clinical, planning/management, technical/research and international comparisons.

The Read codes are an attempt for the first time to include the whole of medicine in one classification~nomenclature for clinicians and managers both to use.

The Read Clinical Classification is a starting point: �9 It exists. �9 It is being used by 10,000 doctors now. �9 It is being used in a wide range of hardware,

software and clinical specialties in primary, secondary and tertiary care.

�9 It is being used successfully in trials linking primary and secondary care by smart cards, modems, hand held computers and other means of electronic communications with the Read codes as the standard means of transfer- ring medical data. The Scottish Home and Health Department

have adopted the Read codes as a standard in primary care, in the hospital sector and as their national drug pharmacy linkage code.

In the UK, the GMSC-RCGP JCG report, 11 published in August 1988, recommended that the Read codes (subject to certain modifica- tions) should be adopted as the UK standard classification for general practice, and it stated that the implications of this should be considered throughout the National Health Service.

On 1 April 1990, the Secretary of State for Health purchased the Read codes and they are now Crown copyright. The extension and evo-

lution of the Read codes are now undertaken by the NHS Centre for Coding and Classification under the control of a supervisory board with members drawn from the medical profession, the Department of Health, OPCS, the BNF and Community Health.

Enquiries relating to the Read Clinical Classi- fication should be addressed to: Computer Aided Medical Systems Limited. 26-28 Leic- ester Road, Loughborough, Leicestershire L E l l 2AG. UK.

References 1 Read JD and Benson TJR. Comprehensive Coding. British

Journal of Healthcare Computing 1986; 3: 22-25. 2 DRGs and Health Care. Ed. Bardsley M, Coles J and Jen-

kins L. King Edward 's Hospital Fund for London 1987. 3 International Classification of Diseases. 9th revision, Clini-

cal Modification, 2nd Edition 1980. US National Commit- tee on Vital and Health Statistics.

4 International Classification of Diseases. Manual of the International Statistical Classification of Diseases, Injuries and Causes of Death. 9th revision. W H O 1977.

5 Classification of Surgical Operations and Procedures. 4th revision. OPCS 1987.

6 Physicians Current Procedural Terminology. 4th edition. American Medical Association 1988.

7 British National Formulary No. 14. Pharmaceutical Press 1987.

8 Steering Group on Health Services Information. Six Reports to the Secretary of State. HMSO 1982-85.

Classification of Occupations and Coding Index. OPCS 1980. 9 Classification of Occupations and Coding Index. OPCS

1980. 10 Drug Tariff, National Health Service, England and Wales.

HMSO April 1990. 11 The Classification of General Practice Data. Final Report of

The GMSC-RCGP Joint Computer Group Technical Working Party. JCG 20, August 1988.

Chapter headings of the Read Clinical Classification CHAPTER DESCRIPTION BASED ON

0 Occupations O P C S 9 1 History/Symptoms Read 1 2 Examinations/Signs Read 1 3 Diagnostic Procedures Read 1 4 Laboratory Procedures Read ~ 5 Radiology/Physics in

Medicine Read 1 6 Preventive Procedures Read ~ 7 Surgical Procedures OPCS--4 s 8 Other Therapeutic

Procedures Read ~ 9 Administration Read 1 @ Health Status Assessment Read 1 A Infectious/Parasitic Diseases ICD-9-CM 3 B Neoplasms ICD-9-CM 3

18 British Homoeopathic Journal

C Endocr ./Nutrit ./Metabol. Disease I C D - 9 - C M 3

D Blood Diseases I C D - 9 - C M 3 E Mental Disorders I C D - 9 - C M 3 F Nerv. System/Sense Organ

Disease I C D - 9 - C M 3 G Circulatory System Diseases I C D - 9 - C M 3 H Respiratory System Diseases I C D - 9 - C M 3 J Digestive System Diseases I C D - 9 - C M 3 K Genitourinary System

Diseases I C D - 9 - C M 3 L Pregnancy/Childbirth/

Puerper ium I C D - 9 - C M 3 M Skin/Subcutaneous Tissue

Disease I C D - 9 - C M 3 N Musculoskelet /Connective

Tissue I C D - 9 - C M 3 P Congenital Anomal ies I C D - 9 - C M 3 Q Perinatal Conditions I C D - 9 - C M 3 R Symptoms/Signs/Ill-defined

Cond. I C D - 9 - C M 3 S Injury and Poisoning I C D - 9 - C M 3 T Causes of Injury and

Poisoning I C D - 9 - C M 3 a Gastro-intestinal System

Drugs BNF 7 b Cardiovascular System Drugs BNF 7 c Respiratory System Drugs BNF 7 d Central Nervous System

Drugs BNF 7 e Infection Drugs BNF 7 f Endocrine System Drugs BNF 7 g Obst /Gynae/Urinary Drugs BNF 7 h Mal ignant / Immunosuppress

Drugs BNF 7 j Nutri t ion and Blood Drugs BNF 7 k Musculoskeletal/Joint Drugs BNF 7 1 Eye Drugs BNF 7

m Ear/Nose/Throat Drugs BNF 7 n Skin Drugs BNF 7 p Immunology Drugs/Vaccines BNF 7 q Anaesthet ics BNF 7 r Dressings/Appliances Read 1 s Incontinence Appliances Read 1 t Diagnostic Agents Read 1 u Stoma Appliances Read ~ v Homeeopathic Agents Read ~

The first two hierarchical levels of the 5-digit Read codes Chapters A- T and 7 . . . . A

. . .A0

.. .A1

. . .A2

. . .A3

. . .A4

.. .A5

. . .A6

. . .A7

Infectious/Parasitic diseases Intestinal infectious diseases Tuberculosis Zoonotic bacterial disease Other bacterial diseases Polio + non-ar thropod CNS virus Viral disease with exan them Arthropod-borne viral diseases Other viral/chlamydial diseas.

. . .A8

. . .A9

. . .AA

. . .AB

. . .AC

. . .AD

. . .AE

. . . . B

. . .BO

...B1

...B2

...B3

.. .B4

...B5

...B6

...B7

...B8

...B9

. . .BA

. . .BB

. . .BZ

. . . . C

...CO

...C1

...C2

...C3

. . .CZ

.... O

. . .DO

.. .D1

. . .D2

. . .D3

. . .D4

. . .DZ

. . .E

. . .EO

. . .E l

. . .E2

. . .E3

. . .EZ

. . . . F

...F0

...F1

. . , F 2

...F3

...F4

...F5

. . .FZ

. . . . G

...GO

...G1

. . .G2

. . .G3

. . .G4

. . .G5

. . .G6

Rickettsioses/arthropod diseas Syphilis + other veneral dis. Other spirochaetal diseases Mycoses Helminthiases Other infectious/parasitic dis Late effects of infectious dis

Neoplasms Carcinoma lip, oral, pharynx Malignant neoplasm GIT Resp. + intrathoracic organ Ca Ca bone, skin, breast, con.tis. Ca genitourinary organ s Ca of other, unspecified site Ca lymphatic/haemopoietic tis. Benign neoplasms Carcinoma in situ Uncertain behaviour neoplasms Unspecified nature neoplasms Morphology of neoplasms Neoplasms NOS

Endo/nutr /met ab/ immun, diseas Disorders of thyroid gland Other endocrine gland diseases Nutritional deficiencies Other metabolic/ immunity dis. Endocr/ntri t /met abol. dis .NOS

Blood/blood forming organs dis Deficiency anaemias Haemolytic anaemias Aplastic and other anaemias Clotting + bleeding disorders White blood cells/other blood Blood/blood forming organ NOS

Mental disorders Organic psychotic conditions Non-organic psychoses Neuroses + other mental disorder Mental retardat ion Mental disorders NOS

Nervous system/sense organ dis Inflammatory disease of CNS Heredi tary/degen.CNS disease Other CNS disorders Peripheral nervous system dis. Disorders of eye and adnexa Ear/mastoid process diseases Nervous system/sense organ NOS

Circulatory system diseases Acute rheumatic fever Chronic rheumatic heart diseas Hypertensive disease Ischaemic heart disease Pulmonary circulation diseases Other forms of heart disease Cerebrovascular disease

Volume 80, Number 1, January 1991

...G7

...G8

.. .GZ

. . . . a

...H0

...H1

...H2

...H3

...H4

...H5

.. .HZ

. . . . J

...J0

...J1

...J2

...J3

...J4

...J5

...J6

...JZ

. . . . g

...K0

...KI

...K2

...K3

...K4

...K5

...KZ

. . . . L

...L0

...L1

...L2

...L3

...L4

...LZ

Artery/arteriole/capillary dis Vein/lymphatic disease + CVS NOS Circulatory system dis.NOS

Respiratory system diseases Acute respiratory infections Other upper resp.tract disease Pneumonia and influenza Chronic obstructive pulm.dis Lung disease due to ext.agents Other resp.system diseases Respiratory system dis.NOS

Digestive system diseases Oral/salivary/jaw diseases Oesophag/stomach/duoden diseas Appendicitis Hernia of abdominal cavity Noninfective enteritis/colitis Other intestine/peritoneum dis Liver/biliary/pancreas + GIT NOS Digestive system diseases NOS

Genitourinary system diseases Nephritis/nephrosis/neph. syndr Other urinary system diseases Male genital organ diseases Disorders of breast Female pelvic inflamm.diseases Other female genital tract dis Genitourinary disease NOS

Pregnancy/childbr th/puerperium Pregnancy + abortive outcome Pregnancy complications Risk factors in pregnancy Labour/delivery complications Puerperium complications Obstetric disorders NOS

. . . . M

...M0

...M1

...M2

...MZ

Skin/subcutaneous tissu diseas Skin/subcutaneous infections Other skin.subcut.inflam.dis Other skin/subcutan, disorders Skin/subcutaneous disease NOS

. . . . N

...N0

...N1

...N2

...N3

...NZ

Musculoskeletal/connectiv tissue Arthropathies and related dis. Vertebral column syndromes Rheumatism excl.the back Musculosk.inflam/deform. + other Musculoskeletal diseases NOS

. . . . P

...P0

...P1

...P2

...P3

...P4

...P5

...P6

...P7

Congenital anomalies Anencephalus + similar anomal Spina bifida Other nerv.sys.congenital anom Congenital eye anomalies Ear/face/neck congenital anom. Bulb.cordis/cardiac sept.anom. Other congenital heart anomalies Other congen.circ, syst. anomal.

...P8

...P9

...PA

...PB

...PC

...PD

...PE

...PF

...PG

...PH

...PJ

...PK

...PZ

. . . . O

...Q0

...Q1

...Q2

...Q3

...Q4

.. .QZ

. . . . R

...R0

...R1

...R2

...RZ

. . . . S

...S0

...S1

...$2

...$3

...$4 ,..$5 ...$6 ...$7 ,..88 ,..89 ,..SA ,..SB ...SC ...SD ...SE ...SF ...SG ...SH ...SJ ...SK ...SL ...SM ...SN ...SP ...SZ

. . . . T

...T0

...T1

...T2

...T3

...T4

...T5

Resp.system congenital anomal. Cleft palate and lip Other congen.upper GIT anomal. Other congen.digestive anom. Congen.genital organ anomalies Urinary system cong.anomalies Congen.musculoskeletal deform. Other congen.limb anomalies Other musculoskeletal anomal. Congen. integument anomalies Chromosomal anomalies Other congenital anomalies Congenital anomaly NOS

Perinatal Conditions Maternal prob. affect, foet/neon Foetal growth/birthwt ./gestn. Birth trauma/asphyxia/hypoxia Foetus/newborn resp.condition Other perinatal conditions Perinatal conditions NOS

Symptoms,signs,ill-def.condit. Symptoms Nonspecific abnormal findings Morbidity/mortality unsure Symptoms,signs,ill-defined NOS

Injury and poisoning Fracture of skull Fracture of neck and trunk Fracture of upper limb Fracture of lower limb Dislocations Sprains and strains lntracranial inj.excl. + skull # Internal inj. chest/abd./pelvis Open wound head/neck/trunk Open wound of upper limb Open wound of lower limb Injury to blood vessels Late effects-injury/poisoning Superficial injury Contusion (bruise) + intact skin Crushing injury Foreign body (FB) in orifice Burns Nerve/spinal cord injuries Traumatic complic.unsp.inj. Poisoning Nonmedic.agent toxic effects Other external effect causes Surgical/medical care com.NEC Injury and poisoning NOS

Causes of injury and poisoning Railway accidents Motor vehic.trafflc acc. (MTVA) Motor veh.non-traff.acc.-MVNTA Other road vehicle accidents Water transport accidents Air/space transport accidents

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20 British Homoeopathic Journal

...T6

...T7

...T8

...T9

...TA

...TB

...TC

...TD

...TE

...TF

...TG

...TH _.TJ ...TK ...TL ...TM ...TN ...TP ...TZ

. . . . 7

...70

Vehicle accidents NEC Place of accid/poisoning (A/P) Accidental poisoning by drugs Other poisoning--non drug Medical accidents to patients Medical proced.compl.-no blame Accidental falls Accidents caused by fire/flame Accid.due to nature + environm. Accid.-sumbers./suffocat. + FB's Other accidents Late effects of accid, injury Drug--adverse reaction--AB Suicide + self-inflict.inj.--SII Homicide + assault Legal intervention injury Injury--?accidental,?purpose Injury from war operations Causes of injury + poisoning NOS

Operations and Procedures Nervous System operations

...71

...72

...73

...74

...75

...76

...77

...78

...79

...7A

...7B

...7C

...7D

...7E

...7F

...7G

...7H

...7J

...7K

...7L

...7M

...7N

...7Z

Endocrine/breast operatn. Eye operations Ear operations Respiratory tract operat. Mouth operations Upper digestive operatns. Lower digestive operatns. Other adb organ operatns. Heart operations Arteries/veins operations Urinary operations Male genital organ operat Lower female genital ops. Upper female genital ops. Obstetrics operations Skin operations Soft tissue operations Skull/spine operations Other bones/joints ops. Miscellaneous operations. Subsid classfctn methods of op Subsid classfctn sites of op Operations and Procedures NOS

Address for correspondence Dr James Read NHS Centre for Coding and Classification 26-28 Leicester Road Loughborough Leics. LEll 2AG

The Read clinical classification (Read codes): General description

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