Background | Understanding the purpose of this change
Differences between ICD-9 and ICD-10
Impact on Physician Practices


The intent of the International Classification of Diseases was to gather statistical data for the international exchange of mortality data. The first edition was clinically modified for use in the United States and published by the World Health Organization (WHO) in 1959. The 10th revision aims not only clarify content and purpose but also to show how the scope of the classification has moved beyond the coding of disease and injuries to the coding of ambulatory care conditions and risk factors frequently encountered in primary care. ICD-10 increases the clinical detail and addresses information about previously classified diseases in addition to diseases discovered since the last revision.

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Understanding the purpose of this change

Over the years, science and technology have allowed us to create new procedures and detect new diseases. With this advancement, the government argued that ICD-9-CM was now unable to accommodate these nuances, as many of the categories have become full, making it difficult to create new codes. In 1994, WHO created and developed ICD-10 to provide increased detail for non-acute conditions. There are two coding systems that fall under ICD-10. The first is ICD-10-PCS, which will replace Volume 3 of ICD-9, the reporting for procedures performed in the hospital. The second system is known as ICD-10-CM, which will replace Volumes 1&2 of ICD-9, the diagnosis codes used by providers.

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Differences between ICD-9 and ICD-10

There are three volumes in ICD-10:

  • Volume 1: Contains the listing of alphanumeric codes with the same hierarchical organization of ICD-9. All codes with the same first three digits have common traits with each digit beyond the third digit adding more specificity. Like ICD-9-CM, you must code to the level of specificity when applicable (e.g., K35 Acute appendicitis is an invalid code because there is a fourth digit subcategories K35.0 acute appendicitis with generalized peritonitis).
  • Volume 2: Is the Instruction Manual. Coders will need to remember that Volume 2 may refer to instructions and not the index, which is what Volume 2 provides in ICD-9-CM.
  • Volume 3: Will provide the index to the codes in the tabular list (unlike ICD-9-CM, which represented a listing of procedural codes). This listing will look the same as ICD-9-CM, terms are found alphabetically, by diagnosis.

Some of the other key differences in ICD-10-CM include:

  • The codes are alphanumeric and include all letters except “U” (caution will need to be made for those codes utilizing “I” or “O”;
  • V and E codes from ICD-9-CM have been incorporated into the main classification in ICD-10-CM;
  • ICD-10-CM can have a maximum of seven digits as opposed to five in ICD-9-CM, which allows for future expansion;
  • ICD-10-CM offers the addition of information relative to ambulatory and managed care encounters;
  • Conditions that are new or that were not uniquely identified in ICD-9-CM have been assigned number;
  • Each “excludes” note has a unique meaning;
  • More coding combinations are used for symptom and diagnosis and etiology and manifestations;
  • Codes have been restructured among chapters.

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Impact on Physician Practices

The transition to a replacement diagnosis and inpatient procedure classification system in the United States will be extremely challenging for physician practices. Due to the fact that virtually every health care electronic system is designed to accept ICD-9-CM, there will be substantial implementation costs for hardware and software upgrades. As with the transition to HIPAA’s electronic transaction standards, physician practices will have to rely on software vendors to develop appropriate ICD-10 upgrades to existing practice management systems as well as stand-alone products. It is not just billing software that will be impacted.

Scheduling, finance, performance, intensive care/emergency room, and decision support products will have to be modified. There is also a concern that this increased documentation requirement with ICD-10 will result in a reduction in physician and other clinical staff productivity -- providers will have to better document to support a higher level of specificity. In addition, significant funds will have to be expended on “cross-walk” software by practices that engage in complex code-based longitudinal benchmarking. Finally, the large increase in the number of diagnosis codes (ICD-10-CM is now at almost 70,000) will necessitate intensive and costly training for both administrative and clinical staff.

MGMA and other organizations sponsored a report on ICD-10 implementation costs for physician practices.

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