Step 3: REFINE

Step 3: REFINE

REFINE Select the row(s) of an entry that meet the requirements of the applied mapping.

What is the purpose of the applied mapping? Does the applied mapping require that the code in the source system be mapped to only one “best” alternative in the target system? Will the correct applied mapping vary depending on the documentation in the record?

Once the user has analyzed all rows for an entry in a GEM, it is possible to select the row or rows most appropriate to an applied mapping. We will use two different sample entries—one combination entry from the ICD-9 to ICD-10 GEM and one single entry from the ICD-10 to ICD-9 GEM—in order to discuss the process of refining an entry and deriving an applied mapping.

Sample Entry 1—ICD-9 to ICD-10 GEM
896.2 Traumatic amputation of foot (complete) (partial), bilateral, without mention of complication

ICD-9 Code	ICD-9 Description	ICD-10 Code	ICD-10 Description	Approximate [FLAG]	No Map [FLAG]	Combination [FLAG]	Scenario	Choice list
896.2	Traumatic amputation of foot (complete) (partial), bilateral, without mention of complication	S98.011A	Complete traumatic amputation of right foot at ankle level, initial encounter	1	0	1	1	1
896.2	Traumatic amputation of foot (complete) (partial), bilateral, without mention of complication	S98.012A	Partial traumatic amputation of left foot at ankle level, initial encounter	1	0	1	1	2
896.2	Traumatic amputation of foot (complete) (partial), bilateral, without mention of complication	S98.021A	Complete traumatic amputation of right foot at ankle level, initial encounter	1	0	1	1	1
896.2	Traumatic amputation of foot (complete) (partial), bilateral, without mention of complication	S98.022A	Partial traumatic amputation of left foot at ankle level, initial encounter	1	0	1	1	2

In this instance the ICD-9 code specifies that the traumatic amputation is bilateral but does not specify whether it is partial or complete. Since both types of information—left or right foot, and whether the amputation is partial or complete—are specified in separate codes in ICD-10, the entry in the ICD-9 to ICD-10 GEM is a combination entry. There are two choice lists in this entry, because two codes in ICD-10 are required to satisfy the equivalent meaning in the ICD-9 combination code. And because the injury can be partial on one side and complete on the other, both sides partial, or both sides complete, there are two choices in each choice list.

After collating the combination entries into their respective choice lists (there is only one scenario), the four valid clusters are:

ICD-9-CM Source	to	ICD-10-CM Target
896.2 Traumatic amputation of foot (complete) (partial), bilateral, without mention of complication	≈ ≈ ≈ ≈	S98.011A Complete traumatic amputation of right foot at ankle level AND S98.012A Complete traumatic amputation of left foot at ankle level
		OR
		S98.011A Complete traumatic amputation of right foot at ankle level AND S98.022A Partial traumatic amputation of left foot at ankle level
		OR
		S98.021A Partial traumatic amputation of right foot at ankle level AND S98.012A Complete traumatic amputation of left foot at ankle level
		OR
		S98.021A Partial traumatic amputation of right foot at ankle level AND S98.022A Partial traumatic amputation of left foot at ankle level

To refine this entry, first the user must decide whether or not it is possible to choose a single cluster—the correct combination of left and right, partial and complete—and if possible, whether or not it is necessary. This decision of course depends on the use of the mapping.

A health information professional or health statistics researcher who is converting a limited number of old ICD-9 records to ICD-10, and has access to the individual medical record, can make use of the increased specificity in ICD-10 codes to re-code the record directly in ICD-10. The user can simply refer to the original record to see the specific nature of the bilateral traumatic amputation and assign the correct pair of ICD-10 codes to the record.

However, a health statistics analyst or data modeler who is translating aggregate ICD-9 data forward to ICD-10, and has no access to individual medical records, cannot make use of the fine distinctions in ICD-10 since they are not present in the old data. In this case, choosing a single cluster that is the closest equivalent cannot be the goal. The user must choose an ICD-10 code or pair of codes to represent all the ICD-10 alternatives, and could choose to fashion a rule by which to map similar cases. Rules specific to the applied mapping would promote consistency and document the decisions made. For example, here the applied mapping could use only the partial traumatic amputation codes.


Sample Entry 2—ICD-10 to ICD-9 GEM:
G92 Toxic encephalopathy

ICD-10 Code	ICD-10 Description	ICD-9 Code	ICD-9 Description	Approximate [FLAG]	No Map [FLAG]	Combination [FLAG]
G92	Toxic encephalopathy	323.71	Toxic encephalitis and encephalomyelitis	1	0	0
G92	Toxic encephalopathy	323.72	Toxic myelitis	1	0	0
G92	Toxic encephalopathy	349.82	Toxic encephalopathy	1	0	0

This same method could be used to translate a record coded in ICD-10 back to ICD-9, and could then be processed by a legacy payment system for reimbursement. The approximate flag is on, indicating that the relationship between the code in the source system and the code in the target system is an approximate equivalent. The approximate flag is on for all three target system ICD-9 code translations of ICD-10 code G92, because the complete meaning of G92 Toxic encephalopathy— as encompassed by the tabular instruction and index entries that refer to G92—includes the clinical concepts toxic encephalitis and encephalomyelitis, toxic myelitis, and toxic encephalopathy specified in three separate ICD-9 diagnosis codes.

To choose among the alternatives in ICD-9 is not possible based on the meaning of the codes themselves. Because the applied mapping is intended to establish general rules for translation rather than deciding on a case-by-case basis, then a consistent method must be derived and documented for resolving the disparity in classification between the two systems. Depending on the applied mapping, the user may choose the closest matching code description or the most frequently recorded of the ICD-9 code alternatives based on ICD-9 data.

For example, for mapping research data on toxic encephalitis during a period that overlaps the use of both ICD-10 and ICD-9, a valid one-to-one mapping from G92 to 323.72 could be derived. But for patient records coded in ICD-10 and mapped internally to an ICD-9 based medical necessity edit system during the transition period, it would depend on the classification of the ICD-9 code alternatives in the edit system. If all three ICD-9 codes were included in the same edit grouping, a valid one-to-one applied mapping to any of the three ICD-9 mapping choices could be derived.