INTRODUCRTI0N
Morbidity and mortality data are important measures of the health of populations. The systematic recording, reporting and dissemination of such data constitute an efficient health information management system (HIMS) that is able to provide valid, reliable and comparable measures of public health considered critical for health policy and planning.1 Presently, the coverage of the topic of health information system is suboptimal in the formal training of physicians, health administrators and other allied health personnel.

HISTORY OF CLASSIFICATION OF DISEASES

Classifications have been used to describe diseases over the ages. Since the seventeenth century, pioneers such as John Graunt, William Farr, Florence Nightingale and Jacques Bertillon attempted to classify diseases systematically. Subsequently, WHO has been responsible for continued revisions of the Bertillon classification; the current version is the tenth revision of the International Classification of Diseases and Related Health Problems (ICD-10).2
   Clinical coding is defined as the translation of diagnoses of diseases, health-related problems and procedural concepts from text to alphabetic/numeric codes for easy storage, retrieval, and uniformity of comparison and analyses.3 Morbidity and mortality data constitute a very useful tool for health planners and administrators to identify priorities for public health interventions, budgeting, future research needs and preparation of guidelines.

AN OVERVIEW OF THE ICD-10 CLASSIFICATION

The ICD-10 is a hierarchical classification containing a list of code categories describing all disease concepts. There are 3 key elements to the structure of ICD-10:4

1. It has 3 volumes. Volume I is a tabular listing of diseases, volume II is an instruction manual and volume III is an alphabetical index of all diseases.

2. The ICD-10 contains 22 chapters, each identified by a Roman numeral and associated alphabet(s) (Table I). These 22 chapters cover 2046 disease categories.

Table I. Classification of diseases in the International Classification of Diseases-10

3. The alphanumeric structure of the code uses one letter followed by 2 or 3 numeric characters, e.g. A15 (first character from A to Z, followed by 2 digits). Three-character coding is used for public health purposes. Most categories are further divided into subcategories to enable coding of a disease condition more specifically, e.g. A15.1 (first character from A to Z, followed by 2 digits, then a decimal point and finally another digit). Specifically, A15 is respiratory tuberculosis, bacteriologically and histologically confirmed; A15.0 is tuberculosis of the lung, confirmed by sputum microscopy with or without culture, and A15.1 is tuberculosis of the lung, confirmed by culture only.

AN OVERVIEW OF MORBIDITY CODING
In the context of ICD, the term morbidity covers illnesses, injuries and reasons for contact with health services including screening and preventive care. Coding usually relates to an ‘episode of healthcare’ (inpatient or ambulatory care) in an institution but may also apply to surveys or other diagnostic data.

Concepts for morbidity coding
At the end of an episode of care, the clinician should record all conditions that affected the person during that period. A health authority may decide on either single-condition coding or multi-condition coding. Clinicians and coders will find their task easy if the patient is treated for only one condition. However, in many instances there may be more than one disease in the same person necessitating the need to differentiate between the ‘main condition’ and the ‘other conditions’. The main condition is defined as the diagnosis established at the end of the episode of healthcare to be the condition primarily responsible for the patient receiving treatment or being investigated. The ‘other conditions’ are those that exist or develop during the episode of healthcare.

Re-selection of main condition
In some instances, the main condition recorded by the clinician may not be consistent with the WHO definition or may not have been specified. WHO has developed a set of rules to ensure that the correct main condition is selected and coded for the particular episode of care (illustrations for these are provided in ICD, Vol. II).3,4 Medical records personnel need to familiarize themselves with these rules to be able to apply them appropriately.

AN OVERVIEW OF MORTALITY CODING
Death certificates are the main source of mortality data. In some settings, verbal autopsy reports may be available where deaths do not occur under medical care. The person certifying the cause of death has to enter the sequence of events leading to death on the International Death Certificate specified by WHO (Table II). This has 2 parts.

1. Part I is used for diseases related to the sequence of events leading directly to death. It has 3–4 lines to record the sequence of events leading to death, in reverse order. Each event in the sequence should be recorded on a separate line—the direct cause of death is entered on the first line, the underlying cause of death is entered on the lowest used line, and any intervening causes on the lines between the first and the lowest used line.

2. Part II is used for co-morbid conditions that have no direct connection with the events leading to death but which, by their nature, contributed to death.

Underlying cause of death
Many death certificates give only one cause of death. However, if 2 or more diseases have contributed to death, all must be recorded on the certificate. In such cases, it has been customary to select one of the causes of death for coding and reporting purposes. This single cause is called the underlying cause of death. The concept of the underlying cause of death is central to mortality coding. WHO defines the underlying cause of death as:

1. The disease or injury which initiated the train of morbid events leading directly to death; or

2. The circumstances of the accident or violence which produced the fatal injury.

   WHO has defined a set of rules to be followed for coding the underlying cause of death.3,4
   Globally, disease classification systems have been used to obtain quantitative estimates of the relative magnitude of diseases, injuries and their risk factors through the Global Burden of Diseases and Risk Factors study.5 There have also been attempts to translate the knowledge from this output for relevant application in the spheres of health policy and practice in developing countries through the Disease Control Priorities project.6

MEDICAL CODING IN INDIA: THE PRESENT STATUS AND THE WAY FORWARD
The main requirements for the implementation of ICD-10 are:4

1. support from regional/institutional administrators

2. the ICD-10 material for morbidity and mortality coding

3. human and financial resources

1. awareness of the WHO ICD-10 system of recording and reporting

2. personnel with adequate expertise in using the ICD-10 material

3. funds for training, manuals, etc.

4. graded introduction of the ICD-10 into the public and/
   or private healthcare systems

5. in-built system of querying (by nosologists) of incorrectly/poorly written statements

Table II. International form of medical certificate of cause of death

6. commitment to the enhanced use of coded information in decision-making.

4. Supporting the use of informatics.

   In India, the ICD is being used in public health research as well as hospital information systems. Population-based epidemiological studies in Tamil Nadu7 and Andhra Pradesh8 have utilized verbal autopsy along with clinical coding to depict the ongoing epidemiological transition in southern India where cardiovascular diseases, injuries, cancers, tuberculosis and chronic respiratory illness are the major causes of death. The Million Death Study conducted jointly by the Registrar General of India and the Centre for Global Health Research at the University of Toronto, Canada, has provided information on maternal mortality in India9 and will soon provide reliable estimates of the main causes of child and adult deaths representative of the entire country.10 Similar cause-of-death studies using the ICD are also being conducted in other developing countries such as China, Tanzania and South Africa.11,12 In another investigation in Mumbai using the ICD, it was possible to study mortality attributable to the use of tobacco for furthering public health action.13
   However, morbidity and mortality coding is yet to be implemented in a uniform manner throughout India. A ‘National List of Diseases’, based on the ICD-10, is being used in hospitals through the Medical Certification of Cause of Death (MCCD) system for mortality coding and for morbidity statistics in some hospitals.14,15 Few instances of effective use of hospital data using the ICD coding systems for auditing clinical care are available from India.16 In the private sector, the ICD-10 is used mainly for medical coding and billing work for insurance purposes, and also as outsourced work by firms for clients in developed countries.17
   Where coding is done in hospital settings, the main problem seems to be inadequate training of practising physicians and coders. The importance of writing up the cause-of-death report is not adequately emphasized and taught to medical practitioners. Most physicians ascribe the cause of death to the mechanism of death (e.g. cardiorespiratory arrest) rather than the underlying cause of death. In other instances, faced with a situation of inadequate information in case records of patients, the physician writing the cause of death report tends to assign the death to the ‘unclassifiable’ category or to some miscellaneous codes. Poor maintenance of medical records also contributes to inaccurate assignment of the cause of death.18 However, this problem is not unique to India; it appears to be a problem in both developed and developing countries.19–23 While the problem is almost universal, the fact that it can be minimized has been shown through simple educational interventions aimed at medical students and residents.19–21,23,24 In some instances, the obligation of statutory requirements may also be effective.24
    The Ministries of Health, Home Affairs and Information Technology of the Government of India have identified the ICD-10 as the most suitable coding system for India compared with other systems.4,25,26 The Directors of Health Services of all states/Union Territories have been advised to adopt the ICD-10 classification system for coding morbidity and mortality records. The Central Bureau of Health Intelligence (CBHI), the national nodal institution for health statistics in the Ministry of Health and Family Welfare, Government of India, has introduced an ‘Orientation training course on ICD-10’ to build capacity among officials engaged in preparation, handling and maintenance of health data.4 More such training programmes are needed to improve knowledge and skills in the fields of disease classification, coding and medical record-keeping and thereby improve the quality of health information generated by hospitals and surveys. Similar courses should be of benefit to health managers, hospital administrators, practising physicians and medical coders. For medical coders, additional inputs on medical terminology, anatomy and physiology would also be required. Results of coding activities should be fed back to clinicians and coders for continuous improve-ment in quality. Technical support in information technology is also required for successful implementation of the health information system.
   In summary, recording and reporting systems need to be strengthened in India through human, financial and technological inputs for improved morbidity and mortality statistics, which are essential for evidence-based decision-making.

REFERENCES

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2. World Health Organization. History of the development of ICD. Available at http://www.who.int/classifications/icd/en/HistoryOfICD.pdf (accessed on 20 August 2005).

3. World Health Organization. International Statistical Classification of Diseases and Related Health Problems. 10th revision. Current version. Version for 2003. Available at http://www.who.int/classifications/icd/en/ (accessed on 8 March 2005).

4. Central Bureau of Health Intelligence. Module and workbook: Orientation training on ICD-10. New Delhi:Directorate General of Health Services, Ministry of Health and Family Welfare, Nirman Bhavan. Available at www.cbhidghs.nic.in (accessed on 15 June 2005).

5. Lopez AD, Mathers CD, Ezzati M, Jamison DT, Murray CJL (eds). Global burden of disease and risk factors. New York:Oxford University Press; 2006.

6. The World Bank. Disease control priorities project. New York:Oxford University Press; 2006. Available at http://www.dcp2.org/main/Home.html (accessed on
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7. Gajalakshmi V, Peto R, Kanaka S, Balasubramanian S. Verbal autopsy of 48 000 adult deaths attributable to medical causes in Chennai (formerly Madras), India. BMC Public Health 2002;2:7.

8. Joshi R, Cardona M, Iyengar S, Sukumar A, Raju CR, Raju KR, et al. Chronic diseases now a leading cause of death in rural India—mortality data from the Andhra Pradesh Rural Health Initiative. Int J Epidemiol 2006;35:1522–9.

9. Registrar General, India. Maternal mortality in India: 1997–2003. Trends, causes and risk factors. New Delhi:Registrar General of India. Available at www. censusindia.net/Maternal_Mortality_in_India_1997–2003 (accessed on 22 December 2006).

10. Jha P, Gajalakshmi V, Gupta PC, Kumar R, Mony P, Dhingra N, et al. RGI–CGHR Prospective Study Collaborators. Prospective study of one million deaths in India: Rationale, design, and validation results. PLoS Med 2006;3:e18.

11. Setel PW, Rao C, Hemed Y, Whiting DR, Yang G, Chandramohan D, et al. Core verbal autopsy procedures with comparative validation results from two countries. PLoS Med 2006;3:e268.

12. Bradshaw D, Groenewald P, Bourne DE, Mahomed H, Nojilana B, Daniels J, et al. Making COD statistics useful for public health at local level in the city of Cape Town. Bull World Health Organ 2006;84:211–17.

13. Gupta PC, Pednekar MS, Parkin DM, Sankaranarayanan R. Tobacco associated mortality in Mumbai (Bombay) India: Results of the Bombay Cohort Study. Int J Epidemiol 2005;34:1395–402.

14. United Nations. Department of Economic and Social Affairs—Statistics Division. Meeting of the Expert Group on International Economic and Social Classifications, New York, 18–20 June 2001. Status of different international/national classifications in India. Available at http://unstats.un.org/unsd/class/intercop/expertgroup/2001/ac78-12.htm (accessed on 28 June 2005).

15. World Health Organization. ICD-10 implementation in WHO member states. Available at http://www.who.int/classifications/icd/implementation/en/ (accessed on 27 June 2005)

16. Ngoc NT, Merialdi M, Abdel-Aleem H, Carroli G, Purwar M, Zavaleta N, et al. Causes of stillbirths and early neonatal deaths: Data from 7993 pregnancies in six developing countries. Bull World Health Organ 2006;84:699–705.

17. Outsource2India.com. Medical coding and billing training in India. Available at www.outsource2india.com/services/medical_billing_training.asp (accessed on 28 June 2005).

18. Mahapatra P, Chalapati Rao PV. Cause of death reporting systems in India: A performance analysis. Natl Med J India 2001;14:154–62.

19. Myers KA, Farquhar DR. Improving the accuracy of death certification. CMAJ 1998;158:1317–23.

20. Lakkireddy DR, Basarakodu KR, Vacek JL, Kondur AK, Ramachandruni SK, Esterbrooks DJ, et al. Improving death certificate completion: A trial of two training interventions. J Gen Intern Med 2007;22:544–8.

21. Pritt BS, Hardin NJ, Richmond JA, Shapiro SL. Death certification errors at an academic institution. Arch Pathol Lab Med 2005;129:1476–9.

22. Tangcharoensathien V, Faramnuayphol P, Teokul W, Bundhamcharoen K, Wibulpholprasert S. A critical assessment of mortality statistics in Thailand: Potential for improvements. Bull World Health Organ 2006;84:233–8.

23. Selinger CP, Ellis RA, Harrington MG. A good death certificate: Improved performance by simple educational measures. Postgrad Med J 2007;83:285–6.

24. Swift B, West K. Death certification: An audit of practice entering the 21st century. J Clin Pathol 2002;55:275–9.

25. Registrar General, India. Sample Registration System 2002. New Delhi:Registrar General of India; 2004.

26. Ministry of Information Technology. Information technology infrastructure for Health: Clinical standards module. New Delhi:Government of India. Available at http://www.mit.gov.in/telemedicine/annexure2.pdf (accessed on 28 June 2005).

Institute of Population Health and Clinical Research (IPHCR),
St John’s National Academy of Health Sciences,
 Koramangala, Bangalore 560034,
 Karnataka, India

PREM KUMAR MONY
Regional Office for Health and Family Welfare—National Vector-Borne Diseases Control Programme, Kendriya Sadan F Wing,
 Koramangala, Bangalore 560034,
 Karnataka, India