The International Classification of Diseases, Tenth Revision (ICD-10) is a classification system that was established and maintained by the World Health Organization (WHO) along with ten other international centers. ICD-10 provides guidelines for universal comparability in the collection, processing, categorization, and presentation of mortality statistics.

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History of ICD-10

Since 1979, all countries worldwide have adopted the ICD-9 system of disease classification. WHO published the latest revision, ICD-10, in the year 1990. Later on, in 1994, some countries started to use ICD-10 codes. The U.S utilized ICD-9 code sets till 2015. However, it soon became difficult to compare their morbidity data directly with that of other countries, because the latter had changed over to ICD-10. Also, the followers of ICD-10 extolled its superiority, with respect to points such as the following:

  • ICD-9 had become outdated
  • it was not powerful enough to meet the healthcare classification necessities of future generations
  • It lacked clinical diagnostic specifications and medical device coding

Thus, the above features became the major reasons for the adoption of ICD-10 in the U.S and other countries.

Purpose and applicability of ICD

Initially, ICD was employed to classify the reasons for mortality as registered in death certificates. It is also applied for the classification of diseases and other health conditions registered in different health documents. The main objectives of ICD are to permit

  • analysis of systematic records
  • gathering, comparing, and interpreting data of morbidity and mortality from various countries that must be revised at different periods of time.

Subsequently, it included the diagnostic criteria for morbidity due to its extended scope. In this manner ICD was launched as a universal standard for diagnostic classification. Hence, all epidemiological and healthcare services practice ICD for the following purposes:

  • Analysis of health conditions common to mankind
  • Monitoring the frequency and advance of diseases
  • Surveillance of other health conditions in relation to additional causes, for example, examining the traits and situation of an afflicted individual

ICD-9 versus ICD-10

The motive for this new revision is to integrate improvements in our medical understanding of health conditions into the old version. Every successive revision contains the basic elements of the preceding version. ICD-9 is now medically dated in certain aspects. Information regarding patients’ medical status and treatment provided to hospitalized patients is limited. ICD-10 is superior to ICD-9 because of certain additions.

General differences

Although the overall content of ICD-10 and ICD-9 is similar, there are several differences such as

  • ICD-9 is a two-volume set while ICD-10 is a three-volume set.​

Volume-1: Table of contents which includes titles of the conditions cited as reasons for mortality along with the respective codes

Volume-2: Narration, guidance, and coding regulations

Volume-3: Index of diseases, injuries, and causes in alphabetical order along with a table of pharmaceuticals  

  • In ICD-10, there has been a rearrangement of some chapters, changes in several titles, and regrouping of many medical conditions.
  • ICD-10 has nearly double the classification categories of ICD-9
  • Minor changes in the coding regulations for mortality

Code set differences:

The coding format in ICD-9 is restrictive due to the definite number of accessible codes. The code sets used in ICD-10 are “alphanumeric” while in ICD-9 they are numeric codes.

  • ICD-10 employs 3–7 entities while ICD-9 uses 3–5 characters only.
  • The number of procedure codes available in ICD-10 (71,924 codes) is 19 times higher compared to ICD-9 (3,824 codes).
  • There are only 14,025 accessible codes for diagnostic purposes in ICD-9 while in ICD-10 there are 68,823 codes, which is five times greater.

Merits of ICD-10

There are significant advantages to using ICD-10 coding rules. Some of them include

  1. Ease in comparing mortality and morbidity data: The current transition of the U.S. healthcare system from ICD-9 to ICD-10 made it possible to compare the U.S. morbidity data with U.S. mortality records. Also, it became easier to compare U.S. morbidity data with international morbidity information.
  2. Enhanced grade of data: ICD-10 furnishes more elaborate data for measuring medical care service grade, safety, and efficacy. ICD-10 has the potential to improve areas such as the following:
  1. Tracking health conditions: As the granularity of ICD-10 is immensely improved compared to ICD-9, it provides:
  • greater precision in diagnosing the health status of patients
  • detailed code sets that enables practitioners to track even the level of complexity in a particular disease condition
  • high-quality patient care and measurement of outcomes.
  1. Advanced data for epidemiological studies: For instance, ICD-10 CM (clinical modification) requires the full details of injuries and their external reasons. It can also track the severity of injuries through the use of extended characters in code sets. This factor helps epidemiological centers and many healthcare services in identifying additional information regarding injuries.

Codes accessible for other purposes:

  • The pregnancy time period is a new addition in the chapter for pregnancy in ICD-10 codes
  • Expanded postoperative codes enable one to distinguish intraoperative and post procedural complications
  • Designing and advancing the reimbursement system