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The International Classification of Diseases (ICD) is the standard diagnostic tool for epidemiology, health management, and clinical purposes.¹ Published by the World Health Organization (WHO), it is used worldwide to analyze the general health situation of various population groups.¹ The ICD is revised periodically and is currently in its 10^th edition.² The ICD-10 was endorsed in May 1990 by the 43^rd World Health Assembly and officially published in 1992.¹ It has now been cited in more than 20,000 scientific articles and used by more than 100 countries around the world.¹

The ICD-10 provides a system of diagnostic codes for classifying diseases, disorders, injuries, and other related health conditions.¹ Roughly 70,000 different codes in the ICD-10 function as the foundation for the identification of health trends and statistics on an international level.² Other uses of the ICD-10 include monitoring morbidity and mortality statistics, investigating the incidence and prevalence of disease, observing reimbursements and resource allocation trends, and keeping track of safety and quality guidelines.¹ The ICD-10 lists health conditions in a hierarchical fashion that allows for easy navigation of health information, assessment of health data between regions, and data comparisons in the same location across different time periods.¹  

The classifications of disease and other health conditions in the ICD-10 have provided universal criteria that facilitate epidemiological studies.³ By definition, epidemiology is the scientific study of the distribution and determinants of health-related states and events in specified populations.⁴ The role of the ICD-10 in epidemiology has most frequently been to provide a standardized means of diagnosing disease or related health conditions.¹ One example is a recent study completed by researchers in South Korea that aimed to evaluate the epidemiology and risk factors of coccyx fracture.⁵ The researchers identified coccyx fractures, which occurred during a period of 9 years from 2010 to 2018 in South Korea, using nationwide data provided by the Korean Health Insurance Review Assessment.⁵ The ICD-10 code S332 was used to identify coccyx fractures.⁵ A total of 238,906 patients were diagnosed with coccyx fracture from 2010 to 2018 using the ICD-10 criteria.⁵ The results provided valuable epidemiological information of this condition, such as the annual incidence (119.75/100,000) and seasonal variation (most frequent in winter, followed by summer).⁵ 

A second example is a study completed by researchers in southeastern Iran that aimed to document the epidemiological features and outcomes of burn injuries in the region.⁶ The retrospective cross-sectional study was carried out at Khatam-Al-Anbiya Hospital, where the researchers analyzed thousands of inpatient records from April 2007 to March 2016.⁶ Burn patients’ records were selected according to the ICD-10 categories for burns and corrosions, codes T20-T32.⁶ According to the researchers, ICD-10 guidelines were used for two reasons.⁶ First, the ICD-10 contains detailed data on burns, including the site, severity, percentage, cause, and location of burn occurrence.⁶ Second, the documentation of burn data, based on ICD-10 directives, standardizes findings from burn injury analyses and leads to the comparability of data at national and international levels.⁶ After analyzing 3,030 burn patients, the results indicated important information about burn trends in southeastern Iran over a 10-year period.⁶ 

Developed by the World Health Organization, the ICD-10 functions as the international standard for defining and reporting diseases and health conditions.⁷ Its use in epidemiological studies enables more direct comparability of data both between regions and within the same region over a period of time.⁷ Through its extensive list of codes, the ICD-10 allows the world to compare and share health information using a common language.⁷

References

1. World Health Organization. (2020). Family of International Classifications (FIC). World Health Organization. https://www.who.int/classifications/en/.

2. National Center for Health Statistics. (2015). International Classification of Diseases, (ICD-10-CM/PCS) Transition – Background. U.S. Department of Health & Human Services. https://www.cdc.gov/nchs/icd/icd10cm_pcs_background.htm.

3. Lépine, J., & Lellouch, J. (1995). Classification and epidemiology of social phobia. European Archives of Psychiatry and Clinical Neuroscience, 244(6), 290-296. https://doi.org/10.1007/bf02190406.

4. U.S. Department of Health & Human Services. (2011). Principles of Epidemiology in Public Health Practice (pp. 1-511). Atlanta: Centers for Disease Control and Prevention. https://www.cdc.gov/csels/dsepd/ss1978/index.html. 

5. Won, H., Moon, S., Park, J., Kim, J., Kim, H., & Baek, S. et al. (2020). Epidemiology and risk factors of coccyx fracture: A study using national claim database in South Korea. Injury, 51(10), 2278-2282. https://doi.org/10.1016/j.injury.2020.07.019.

6. Alipour, J., Mehdipour, Y., & Karimi, A. (2020). Epidemiology and outcome analysis of 3030 burn patients with an ICD-10 approach. Annals of burns and fire disasters, 33(1), 3–13. https://pubmed.ncbi.nlm.nih.gov/32523489/.

7. World Health Organization. (2012). International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10). WHO Family of International Classifications Network. https://www.cdc.gov/nchs/icd/icd10cm.htm.