ICD-10 Transition

What is ICD-10?

Health care providers in the United States use the International Classification of Diseases (ICD) to record diseases, signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or diseases in patient medical records. They also use it to code medical diagnoses and procedures for care management and billing purposes.

The International Classification of Diseases (ICD), developed by the World Health Organization (WHO), is an international standards-based code set used for epidemiology, health management and clinical purposes, including analyzing population health data. It is used to monitor the incidence and prevalence of diseases and other health problems, providing a picture of the general health situation of countries and populations.

ICD is used by health care providers, researchers, policy-makers, health information technology professionals, insurers and patient organizations to classify diseases and other health problems recorded on many types of health and vital records. In addition to enabling the storage and retrieval of diagnostic information for clinical, epidemiological and quality purposes, these records also provide the basis for the compilation of national mortality and morbidity statistics by WHO Member States. In some countries, including the United States, ICD is used for reimbursement and resource allocation decision-making by countries.

There are many derivatives of the code set, used for different purposes. In the United States, ICD-10-CM and ICD-10-PCS (for inpatient procedures) have been adopted for use for reimbursement and other health-related purposes beginning October 1, 2015. All Health Insurance Portability and Accountability Act (HIPAA) transactions must use ICD-10-CM or ICD-10-PCS codes. Other transactions regarding diagnosis codes or inpatient procedure codes may, but are not required, to used ICD-10-CM or ICD-10-PCS.

How is ICD-10-CM Better than ICD-9-CM?

ICD-10-CM provides greater detail, applies consistent use of terminology, and introduces other improvements. As a result, healthcare providers will make better clinical decisions and may accurately measure patient outcomes and care.

ICD-10-CM provides improved data for understanding causes of health conditions. The update to ICD-10-CM allows for efficient tracking of health care and public health trends, monitoring quality of care issues, and evaluating health outcomes. It affects how providers design payment systems, process claims, and identify fraud or abuse.

Greater Detail

ICD-10-CM provides a greater level of detail, including:

  • Identifying the specific side of body involved
  • Conveying the complexity of disease conditions
  • Providing more precise identification and tracking of specific conditions
  • Documenting severity of injuries, including how and where injuries happened

Consistent Terminology

Terminology and disease classification will be consistent with new technology and current clinical practice.

What are the Differences between ICD-9-CM and ICD-10-CM?

The table below compares ICD-9-CM and ICD-10-CM. ICD-10-CM significantly expands procedure and diagnosis codes, provides alphanumeric categories, and reorganizes conditions into logical groups.

ICD-9-CM Diagnosis Codes ICD-10-CM Diagnosis Codes
Limited data about patients’ medical conditions and hospital inpatient procedures
  • 30 years old
  • Outdated terms
Incorporates greater clinical detail and level of specificity to provide better quality of data.

Supports tracking health care and public health trends, quality of care issues, and evaluation of health outcomes.
No Laterality – Does not specify which side of the body the injury or condition is located Specifies where on the body the injury occurred; “Right” or “Left” account for more than 40 percent of codes
Structure of ICD-9 limits the number of new codes that can be created. Many ICD-9 categories are full.
  • 3-5 characters
  • First character is alpha (E or V) or numeric
  • Characters 2-5 are numeric
  • Decimal point is placed after the third character
Improved structure, capacity, and flexibility for capturing advances in technology and medical knowledge.
  • 3-7 characters
  • Character 1 is alpha; character 2 is numeric
  • Characters 3-7 are alpha or numeric
  • Decimal point is placed after the third character
No placeholder characters “X” placeholders
14,025 codes 69,823 more specific codes
Limited Severity Parameters Extensive Severity Parameters
Limited Combination Codes Extensive Combination Codes to better capture complexity
ICD-9-CM vs. ICD-10-CM


Mental Health Provider Broadcast from MHSA – Aug. 5, 2015 (pdf, 24 kb)

This is a letter distributed by MHSA to the LMHA’s to provide communication about ICD-10-CM implementation.

Sources: World Health Organization – International Classification of Diseases

Last updated June 1, 2016