GEMs: Buyers Beware. Crosswalk and Translation Tools Can Bring Unexpected Risks

By Diana Reed, RHIT, CCS-P

When it comes to converting superbills and claims from ICD-9-CM to ICD-10-CM, many healthcare providers believe that general equivalence mappings (GEMs) offer a cost effective and simple solution. The ability to purchase relatively cheap automated mappings of specialties’ top codes contributes to this sense of security. The mappings are often marketed using terms such as “translation tools” or “crosswalks.” Mappings are useful tools, but it is important that healthcare providers are also advised of the tools’ limitations.

Mapping simply provides a linkage between a code in one set and its closest equivalent in the other code set without consideration of context or specific patient encounter information, whereas coding involves assigning the most appropriate code based on health record documentation, knowledge of other codes in the medical record, and applicable coding guidelines.[1]

GEMs are not a catch-all solution for physician practices, and offer a limited scope of use, according to guidance issued by the Centers for Medicare and Medicaid Services (CMS). Once ICD-10 is implemented, GEMs will be of limited use to most physician practices and may not be appropriate since coding should occur directly to ICD-10 based on actual clinical documentation, rather than mapping from existing ICD-9 codes. In some instances, GEMs can be helpful in validating one’s coding practices to help identify some codes in ICD-10 relative to existing ICD-9 codes for the purpose of training and validation.[2]

Simply put, mappings, crosswalks, or translation tools require human intervention for validation—and they do not substitute for learning the new code set.

GEMs Alone Cannot Replace Validation, Education

The following is an example of how crosswalks or translation guides can be problematic when purchased with no further plans for validation or education.

A gastroenterology practice’s providers were convinced that a purchased crosswalk was all they needed for ICD-10-CM implementation. Their business office assured the providers that they had things under control. But one employee was not so convinced after attending an ICD-10 Basics presentation and sought further options for the practice. An AHIMA credentialed coding consultant was contacted for specialty specific coding education. The consultant requested a list of the practice’s 30 most common codes. Instead, the practice provided the consultant with a copy of their purchased crosswalk and the national top gastroenterology codes. Problems associated with depending on mass-produced specialty specific crosswalks without validation and training were obvious.

ICD-9-CM Inclusion Term not Crosswalked to ICD-10-CM Subcategory Code

Code 535.10, Atrophic gastritis, without mention of hemorrhage in ICD-9-CM was crosswalked to code K29.40, Chronic atrophic gastritis without bleeding in ICD-10-CM. But experienced coders know that code 535.1- is also used for Chronic gastritis, not otherwise stated. That is because “chronic gastritis” is listed as an inclusion term under code 535.1-. No consideration was given to this inclusion term. There is a new subcategory for this condition in ICD-10-CM: K29.50, Unspecified chronic gastritis without bleeding. The table [below] demonstrates how ICD-10-CM has revised the coding for chronic gastritis.

Chronic gastritis can be either atrophic or non-atrophic.[3] ICD-10-CM, with its increased data granularity, takes into account this difference with a separate code for Chronic gastritis, not otherwise stated. Non-specific chronic gastritis should not be confused with Chronic superficial gastritis (K29.3-) which causes pathological changes limited to the upper one-third of the mucosa, or Chronic atrophic gastritis (K29.4-) which involves the full thickness of the mucosa, producing atrophy of gastric glands with loss of cells.

Education is essential in the course of validating a practice’s ICD-9 to ICD-10 crosswalk. Definitions of chronic gastritis should be discussed and providers advised to include the type in the record documentation. And although the crosswalk does not address it, providers should also be aware of the need to assign an additional code for Helicobacter pylori when gastritis is caused by that organism.

Missed New Subcategory Code

As any experienced gastroenterology coder knows, patients frequently receive diagnostic colonoscopies for a complaint of a change in bowel habits. In ICD-9-CM there is not a specific code for this condition. Code 787.99, Other symptoms involving the digestive system is assigned. “Change in bowel habits” is listed as an inclusion term in the tabular list under code 787.99. The purchased crosswalk showed 787.99 mapped to the ICD-10-CM code R19.8, Other specified symptoms and signs involving the digestive system and abdomen. Although this is a correct direct translation, the inclusion term “change in bowel habits” was ignored. There is actually a new code in ICD-10-CM for this condition, R19.4.

Missed Documentation Improvement Training Opportunity

Code 455.0, Internal hemorrhoids without complication, was appropriately crosswalked to six potential ICD-10-CM codes. Four of the codes are structured clinically and providers are now able to designate the grade/degree of severity of hemorrhoids. The other two codes are for other and unspecified. Reviewing these codes with providers presents an opportunity to discuss new documentation requirements and the importance of capturing severity levels.

Potential for Coding Convention Violations

Code 558.9, Other and unspecified noninfectious gastroenteritis and colitis was crosswalked to two ICD-10 codes, one for other specified condition and one for unspecified. Coding conventions state that “other” or “other specified” codes are for use when the information in the health record provides detail for which a specific code does not exist. How would a provider know that a code does not exist for a specific condition unless they were aware of all options?

Specific codes not presented as options on the crosswalk include K52.1, Toxic gastroenteritis and colitis; K52.0, Gastroenteritis and colitis due to radiation; K52.2, Allergic and dietetic gastroenteritis and colitis; K52.81, Eosinophilic gastritis or gastroenteritis; and K52.82, Eosinophilic colitis.

Table 1: Crosswalking Chronic Gastritis from ICD-9-CM to ICD-10-CM

This table demonstrates how ICD-10-CM has revised the coding for chronic gastritis. Terms in parentheses are nonessential modifiers.

Alphabetic Index







Atrophic (chronic)




Chronic (antral)




Tabular List




Atrophic gastritis without mention of hemorrhage

“Atrophic-hyperplastic gastritis” and “Chronic (atrophic) gastritis” are listed as inclusion terms for 535.10 and 535.11.


Chronic atrophic gastritis without bleeding

“Gastric atrophy” is listed as an inclusion term for K29.40 and K29.41


Unspecified chronic gastritis without bleeding

“Chronic antral gastritis” and “Chronic fundal gastritis” are listed as inclusion terms for K29.50 and K29.51

Examples Highlight Need for Crosswalk Validation

These are just a few examples of the problems that arise from an overreliance on GEMs to carry a practice through the transition to ICD-10-CM. The importance of validation of purchased crosswalks and related training cannot be over-emphasized.

The caveat for healthcare providers is that there is no simple crosswalk from ICD-9 to ICD-10 in the GEM files. GEMs may provide a good starting point, but more intelligence is needed for review and clarification. Training is essential for the ICD-9 to ICD-10 conversion. According to CMS, the state Medicaid program, and AHIMA, providers should code natively, which requires learning the ICD-10-CM code set and coding guidelines. Crosswalks or translation tools derived from GEMs are not a substitute for this education and training nor are they an efficient solution when used alone.


[1] AHIMA. “Putting the ICD-10-CM/PCS GEMs into Practice.” May 2013. 

[2] Centers for Medicare and Medicaid Services. “ICD-10 Implementation Guide for Small and Medium Practices.” October 2011.

[3] Rugge, Massimo and Robert M. Genta. “Staging and grading of chronic gastritis.” Human Pathology 36 (2005): 228-233.


Centers for Disease Control and Prevention. “International Classification of Diseases, Ninth Revision, Clinical Modification, (ICD-9-CM).”

Centers for Disease Control and Prevention. “International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM).”

Diana Reed ( is a consultant with Health Information Strategies.

Article citation:
Reed, Diana. "GEMs: Buyers Beware. Crosswalk and Translation Tools Can Bring Unexpected Risks" Journal of AHIMA 86, no.1 (January 2015): 60-62.