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Using General Equivalence Mappings GEMs to help ICD-10 implementation

June 5, 2013

General equivalence mappings (gems) for icd-10 Learning to use the ICD-10 is no simple task. To make the job a little easier, several healthcare industry stakeholders have joined together to create the general equivalence mapping (GEM) system which allows physicians, coders and other healthcare personnel a simpler way to understand which codes area available for which conditions.

The GEM system is designed to provide a bridge from the ICD-9 codes to the new ICD-10 codes in much the same way as a language dictionary helps you translate a word from one language into another. GEM aids coders in moving over to the new system, enabling them to become familiar with the ICD-10 options while relying temporarily on ICD-9 codes. In addition, GEMs allow coding professionals an opportunity to learn the differences between the code sets so they are able to make more informed choices when selecting the ICD-10 codes that most closely match their needs.

GEMs were designed to support all uses of coded data, and for ease of use, the system is bidirectional, which means it can be used to “translate” from ICD-9 to ICD-10 (forward mapping) and from ICD-10 to ICD-9 (backward mapping). This bidirectional features makes it easier for coding professionals to “check their work” and ensure the best possible match. Because the system is being used nationwide, GEMs also ensure consistency in coding use, especially during the initial period of transition. GEMs will also be available for three years beyond the initial compliance date.

Here are a few things you should know about the GEM system:

  • GEM is not a one-to-one mapping between the ICD-9 and the ICD-10.
  • Because the ICD-10 system comprises many more codes than the ICD-9 protocol, many ICD-9 codes will map to more than one ICD-10 code.
  • In some cases, an ICD-9 code will not have a match.
  • Likewise, some ICD-10 codes represent new concepts for which there is no ICD-9 code.
  • More than one ICD-9 code may be needed to completely and correctly understand the ICD-10 correlative.
  • Similarly, for any given ICD-10, there may be more than one possible ICD-9 translation.

To make coding more specific, there are separate sets of GEMs for reimbursement and for diagnosis. Both codes use the same general format and rely on two mappings: one from ICD-9 to ICD-10 and one from ICD-10 to ICD-9. To assist in selecting the correct code, especially when there are multiple codes available, the system also includes specific attributes that characterize the codes and further refine the choices.

When more than one code is offered as a possible match through the GEM system, it’s often because the ICD-10 system includes many more specific diagnoses and procedures than the ICD-9 system; therefore, using GEM all possible matches are offered.

In other cases, multiple codes may result when the classification system has changed under ICD-10; for instance, an obstetrics patient’s diagnosis classification would be made according to the episode of care under ICD-9; under ICD-10, obstetrics patients are classified by stage of pregnancy. In these cases, GEM provides specific rules for linking ICD-9 and ICD-10 codes.

Both the National Center for Health Statistics (NCHS) and the Centers for Medicare and Medicaid Services (CMS) websites offer comprehensive and detailed users guides that feature information about how to use both the diagnostic and procedures GEM systems as well as examples of the system and its use. Users will also find a glossary defining terms specific to the GEM system and an appendix with file names and format information.

Transitioning to ICD-10 is both a time- and labor-intensive process. The GEM system is provided to assist healthcare providers in making the transition as easy as possible.




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