While the initial background research answered the first question “what is the difference between ICD-9-CM and ICD-10-CM”, the Associate Fellow focused on answering the remaining questions to develop the overall methodology:
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What are the options available to facilitate the transition?
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How will MedlinePlus Connect implement the transition to ICD-10-CM?
The Associate Fellow researched methods to facilitate the transition and analyzed two mapping options to determine the feasibility of using them to help MedlinePlus Connect support ICD-10-CM.
PHASE I: RESEARCH GENERAL EQUIVALENCE MAPPINGS
Research on mapping and crosswalks available between ICD-9-CM and ICD-10-CM revealed a dearth of available options. The General Equivalence Mappings (GEMS) are the primary option discussed within the literature, although proprietary ICD-9-CM to ICD-10-CM mapping tools also exist [13]. A number of groups, including the National Center for Health Statistics (NCHS), the Centers for Medicare and Medicaid (CMS), the American Health Information Management Association (AHIMA), the American Hospital Association, and the 3M Health Information Systems helped produce the GEMs [12].
The GEMS provide a network of relationships between ICD-9-CM and ICD-10-CM that can be used to create customized mappings between ICD-9-CM and 10-CM. NCHS and CMS only plan to maintain the GEMs until October 2013. Butler (2007) provides several GEMs definitions:
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a free, “public domain reference mapping …tool to convert and test systems, link data in long-term clinical studies, develop application-specific mappings, and analyze data collected during the transition period”[12]
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“two-way translation dictionaries for diagnosis…they elucidate the differences between the code sets and assist users in making informed decisions about how to link the codes in a way that meets their needs” [12]
The ICD-10-CM GEMs contain two separate GEMs files, described in Table 2 with examples shown in Table 3. Separate forward and backward mapping files are available for diagnosis GEMs7 and procedure GEMs8. Each file contains code pairs containing one code from each code set.
Table : GEMS File Descriptions
GEMS Files
|
Direction
|
Number
| -
Forward mapping file
|
ICD-9-CM to ICD-10-CM
|
23,485 code sets
17,156 code sets with associated Health Topics
| -
Backward mapping file
|
ICD-10-CM to ICD-9-CM
|
78,129 code sets
60,295 code sets with associated Health Topics
|
Table : GEMS Text File Examples
Diagnosis Forward Mappings
9cm to 10cm gem.txt
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Diagnosis Backward Mappings
10cm to 9cm gem.txt
|
ICD9CM ICD10CM Flags
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ICD10CM ICD9CM Flags
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0019 A009 00000
0020 A0100 10000
0021 A011 00000
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A009 0019 00000
A0100 0020 10000
A0101 0020 10000
|
As seen in the examples in Table 2 and Table 3, these GEMs files provide flags, or information necessary to extract and use the code pairs for each end user’s specific need. The flags indicate the type of match found for each code pair. The first three flags are described below and also represented within Table 4.
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Approximate flag: indicates if the source and target entries are considered equivalent (a 1 indicates equivalence and a 0 indicates approximate).
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No map flag: a 1 indicates the code in the source system is not linked to any code in the target system.
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Combination flag: indicates whether or not multiple target system codes are required to satisfy the full meaning of the mapped code from the source system [9]. When the combination code is turned on (set to 1), the two last fields after the flags are used. These fields represent the scenario and choice list fields and allow the user to collate entries with a combination code.
Table : GEMs Flags and Descriptions
Meaning
|
Approximate [Flag]
|
No Map [Flag]
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Combination [Flag]
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No one code in the target system expresses the same essential meaning as the code in the source system
|
1
|
0
|
0
|
The source and target codes are considered equivalent
|
0
|
0
|
0
|
More than one code in the target system is required to satisfy the full equivalent meaning of a code in the source system
|
1
|
0
|
1
|
A code in the source system is not linked to any code in the target system
|
0
|
1
|
0
|
Two additional flags provide context to the combination flag:
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Scenario flag: “A scenario designates one variation of the meaning of the source system diagnosis as specified in a combination code” (GEMS documentation and User’s Guide)
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Choice List: “A scenario is subdivided into two or more choice lists of codes…these are the codes that must be linked together as a unit in an applied mapping to satisfy the equivalent meaning of the combination code in the source system. A choice list contains one or more codes in the target system that expresses a portion of the meaning of the code in the source system” (GEMS documentation and User’s Guide)
The GEMS contain a variety of match types between ICD-9-CM and ICD-10-CM, as shown in Table 5.
Table : Percentages of Types of Matches (from [15])
Mapping Categories
|
ICD-10 to ICD-9
|
ICD-9 to ICD-10
|
No Match
|
1.2%
|
3.0%
|
1-to-1 Exact Match
|
5.0%
|
24.2%
|
1-to-1 Approximate Match with 1 Choice
|
82.6%
|
49.1%
|
1-to-1 Approximate Match with Multiple Choices
|
4.3%
|
18.7%
|
1-to-Many Match with 1 Scenario
|
6.6%
|
2.1%
|
1-to-Many Match with Multiple Scenarios
|
0.2%
|
2.9%
| MEETINGS
The Associate Fellow met with several NLM staff to determine the best method to support ICD-10-CM:
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MedlinePlus Connect team, Public Services Division: Gain a better understand of the MedlinePlus Connect background and project,
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Jan Willis, MEDLARS Management Section: Gain a better idea of the research being conducted on vocabularies at the NLM,
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Kin Wah Fung, Lister Hill Center: Discuss questions related to the current ICD-9-CM / Health Topic mappings, mapping resources available from the NLM, and the GEMs,
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Vivian Auld, National Information Center on Health Services Research and Health Care Technology (NICHSR): Discuss the GEMs and expansions to SNOMED CT CORE Subset,
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Olivier Bodenreider and Lee Peters, Lister Hill Center: Discuss the Lister Hill Center (LHC) - UMLS mapping algorithm.
Each provided valuable insight to the project (notes from select meetings available in APPENDIX E: NOTES FROM SELECT MEETINGS).
The team pursued the following methods of analysis based on the research phase and suggestions from NLM staff:
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Analyze a sample of the ICD-10-CM codes mapped to Health Topics using GEMs to determine the feasibility of using the GEMs to create associations (random sample, select sample, combination sample). The MedlinePlus team will use the GEMs to update the existing ICD-9-CM mapping to ICD-10-CM. This allows the team to use their existing mappings to ICD-9-CM. Based on their research, the team was interested to see if the GEMs could be used to crosswalk the Health Topics from ICD-9-CM to ICD-10-CM.
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Work with Olivier Bodenreider and Lee Peters to run their original algorithm using the UMLS to associate ICD-10-CM codes with MedlinePlus Health Topics. This process requires that the team begin anew. New mappings between ICD-10-CM and the Health Topics will result.
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Compare the two methods to determine the best option for MedlinePlus Connect to support ICD-10-CM.
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