ICD-10 Training

Mapping and Conversion

Although the conversion from ICD-9 to ICD-10 is mandated by the U.S government’s Department of Health and Human Services, there are intrinsic benefits to the change. For physicians and patients, ICD-10 expands the diagnosis coding directory, adding increased specificity and detail, which is important to gaining a better understanding of a diagnosis and determining the proper course of treatment. For payers, the ICD-10 conversion will create more accurate definitions of services rendered by healthcare professionals. Globally, ICD-10 will help facilitate the sharing of more detailed disease information across the globe, vastly enhancing epidemiology.

As the ICD-10 codes become more specific, they also become more complex. ICD-9 codes consist of only three to five digits. The first digit either a number or letter (letters “V” and “E” only); all other digits in an ICD-9 code are numbers. With the increased specificity of ICD-10, codes can be up to seven digits. The first digit in an ICD-10 code is always a letter (any letter but “U”). The second digit is always a number, and the remaining digits can be any combination of numbers and letters. ICD-10-CM utilizes a placeholder character “X”; the “X” is used as a placeholder with certain codes to allow for future expansion.

ICD 9 Mapping Example ICD 9 Example

As the ICD-10 codes become more specific, they also become more complex. ICD-9 codes consist of only three to five digits. The first digit either a number or letter (letters “V” and “E” only); all other digits in an ICD-9 code are numbers.

ICD 10 Mapping Example ICD 10 Example

With the increased specificity of ICD-10, codes can be up to seven digits. The first digit in an ICD-10 code is always a letter (any letter but “U”). The second digit is always a number, and the remaining digits can be any combination of numbers and letters.

The following example of an ICD-10-CM code is for a displaced transverse fracture of the shaft of the humerus, right arm, an initial encounter for closed fracture.

ICD 10 Mapping Increased Specificity Example ICD 10 Increased Specificity Example

The corresponding ICD-9 code would be 812.21, which would only describe a closed fracture of the shaft of the humerus. It’s plain to see; the ICD-10 codes provide far more information.

General Equivalence Mapping (GEM)

General Equivalence Mapping (GEM), often referred to simply as ICD-10 mapping, refers to the mapping tools designed and used to perform an ICD-9 to ICD-10 crosswalk. When performing General Equivalence Mapping, or an ICD-9 to ICD-10 crosswalk, the conversion will not always result in simple one-to-one mapping. While some ICD-9 codes do map directly to an ICD-10 code, it does not always mean the codes match in detail. Many codes will require additional information in order to correctly map the intended ICD-10 code; information such as, cause, location, type of encounter, etc. Some ICD-diagnosis codes, like those pregnancy and obstetrics, will garner a one-to-three crosswalk, depending on the stage and complication of pregnancy. In extreme cases, like the coding of fractures and disorders of the bone and cartilage, the ICD-9 to ICD-10 crosswalk can result in ICD-10 mapping that yields hundreds to thousands of results. For a period of two years or more, systems will need to access both ICD-9-CM codes and ICD-10-CM codes as the country transitions from ICD-9-CM to ICD-10-CM. Mapping will be necessary so that equivalent codes can be found for issues of disease tracking, medical necessity edits and outcomes studies.


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