ICD 10 Coding Alert

Follow this guide to find out what each flag really means.

You have seen plenty of ICD-9 to ICD-10 bridges online, but beware: these bridges are based on GEMs, which are only about 50-percent accurate. If you rely solely on this mapping tool, you are likely to miss important coding subtleties, which could land your claim in limbo land.

Follow this step-by-step explanation to master GEMs and what each digit really means.

Basics: GEMs stand for General Equivalent Mappings. Note: The important term to remember is "general."

The GEMs are the raw material from which providers, health information vendors and payers can derive specific applied mappings to meet their needs. You can use GEMs to study the differences between ICD-9-CM and ICD-10-CM/PCS.

The GEM file is a "flat file," meaning this is a record with no structural relationships. (You can download it here: http://www.cms.gov/ICD10/11b1_2011_ICD10CM_and_GEMs.asp#TopOfPage)

Are GEMs a True Crosswalk?

The word "crosswalk" is often used to refer to code mappings (as in, data element mappings between two distinct data models: ICD-9 and ICD-10), but be advised: GEMs are not true crosswalks. They are reference mappings, to help the user navigate the complexity of translating meaning from one code set to the other. They are tools to help you understand, analyze, and make distinctions that manage the complexity, and to derive their own applied mappings (if that's your goal).

The GEMs are more complex than a simple one-to-one crosswalk, and some statistics say they're only about 50-percent accurate. What GEMs are effective at is reflecting the relative complexity of the code sets clearly. The relationship between them is not simple. GEMs effectively demonstrate this, rather than making the transition from the old to the new code system in an oversimplified way.

What are GEMs Relationships Like?

You can have a variety of different code relationships in the GEMs file. Here are a few:

Some codes have a one-to-one correlation. Code 003.21 (Salmonella meningitis) in ICD-9 matches up to A02.21 (Salmonella meningitis) in ICD-10-CM.

Some codes won't match because of specificity. For instance, 649.53 (Spotting complicating pregnancy) does not, for instance, exactly equal O26.851 (Spotting complicating pregnancy, first trimester). To arrive at the correct code in ICD-10-CM, you have to know the trimester.

Also, ICD-10-CM codes may combine multiple diagnoses or concepts, such as:

• a chronic condition with acute manifestation (G40.911, Epilepsy, unspecified, intractable, with status epilepticus);
• two concurrent acute conditions (R65.21, Severe sepsis with septic shock);
• acute condition with external cause (T39.012A, Poisoning by aspirin, intentional self-harm, initial encounter).

On the other hand, ICD-10-CM code Z72.3 (Lack of physical exercise) doesn't have a ICD-9 target at all.

So given you can have varied code relationships between the old system and the new, that's why you can't count the GEMs file as being cut-and-dried.

What Key Terms Should You Know?

"Target system" means the destination code set. In other words, this is the set the GEM is mapping 'to.'

"Source system" means the original code set. In other words, this is the set the GEM is mapping 'from.'

When you see your ICD-9-CM code targeting an ICD-10-CM code, then that is called "forward mapping."

On the other hand, when you see an ICD-10-CM code targeting an ICD-9-CM code, then that is called "backward mapping."

"Reverse lookup" means that you're using a GEM by looking at a target system code and examining the codes that translate to it.

What is an Example of a GEM?

Let's look at the file itself. Here's an example of what your GEM file looks like.

62130 N8500 00000

In GEM terms, 62130 is your source (which is code 621.30 with your decimal applied); N8500 is your target; and 00000 represents your flags.

Translation: This means 621.30 (Endometrial hyperplasia, unspecified) maps directly to N8500 (Endometrial hyperplasia, unspecified).

How do you know this? Let's focus on the flags, the '00000' number.

What Do the Flags Mean?

Each digit of the '00000' number represents five different flags.

Key: The 0 means off. The 1 means on.

These flags are:

• 1st digit: Approximate Flag
• 2nd digit: No Map Flag
• 3rd digit: Combination Flag
• 4th digit: Scenario Flag
• 5th digit: Choice Flag

Examine the Approximate Flag

"Approximate" is Flag 1, which is in column 1 of the flags. The majority of alternatives are considered an approximate match. "0" means the translation is an identical match. This is rare in the procedure GEMs but more common in the diagnosis GEMs.

Remember this example?

62130 N8500 00000

The first flag is a "0," meaning you already know that 621.30 has an identical match in N8500.

On the other hand, check out this example:

K3189 5363 10000

K3189 5375 10000

K3189 53789 10000

The first flag is a "1," means that the complete meaning of the source code differs from the complete meaning of the target system code. In other words, K31.89 (Other diseases of stomach and duodenum) includes the meanings of all three codes: 536.3 (Gastroparesis), 537.5 (Gastroptosis), and 537.89 (Other specified disorders of stomach and duodenum). This isn't a direct match. All of these meanings are approximate.

Find Out What 'No Map' Flag Means

"No Map" is Flag 2, which is in column 2 of the flags. A "1" means there is no plausible translation for the source system code. A "0" means there is at least one plausible translation for the source code.

Let's refer back to our familiar example:

62130 N8500 00000

This means you have at least one plausible translation for the source code. Code 621.30 has a plausible translation in N8500.

However, look at this example:

T500x6A NODX 11000

Because you see a "1" as Flag 2, you can see that T500x6A (Underdosing of mineralocorticoids and their antagonists, initial encounter) has no plausible translation. The "NODX" means no description found.

Conquer the Combination Flag

"Combination" is Flag 3, the scenario and choice list flags. When you see a 0 in this position, as in our example, this means the code maps to a single code.

62130 N8500 00000

In other words, 621.30 only maps to N8500.

On the other hand, when you see a 1 in this position, this means the code maps to more than 1 code. Look at this example:

I25111 41401 10111

I25111 4139 10112

See the "1" in the third digit? This means that I25.111 (Atherosclerotic heart disease of native coronary artery with angina pectoris with documented spasm) maps to 414.01 (Coronary atherosclerosis of native coronary artery) with 413.9 (Other and unspecified angina pectoris).

Remember: The term "with," means "associated with" or "due to."

Figure Out the Scenario Flag

Now that you have identified Flags 1 through 3, let's examine Flags 4 and 5 (or the fourth and fifth digits).

Flags 4 and 5 clarify combination entries.

For the Scenario Flag (4th digit), you'll see 0 meaning Off, or digits 1-9 meaning, "In a combo entry, this is a collection of codes from the target system containing the necessary codes that combined as directed will satisfy the equivalent meaning of a code in the source system."

Source: General Equivalence Mappings: Documentation for Technical Users (download at http://www.cdc.gov/nchs/icd/icd10cm.htm)

Here's our previous example:

62130 N8500 00000

The "0" turns the Scenario column off, so you know that you don't need to worry about this. But this won't always be the case:

T422X1A 9662 10111

T422X1A E8558 10112

T422X1A 9660 10121

T422X1A E8558 10122

Notice how you have "1" and "2" in the fourth digit column. This breaks down these codes into two scenarios, as follows:

Scenario 1: Code (T42.2x1A, Poisoning by succinimides and oxazolidinediones, accidental [unintentional], initial encounter) maps to 966.2 (Poisoning by succinimides) with E855.8 (Accidental poisoning by other specified drugs acting on central and autonomic nervous systems).

Scenario 2: Code T42.2x1A (Poisoning by succinimides and oxazolidinediones, accidental [unintentional], initial encounter) maps to 966.0 (Poisoning by oxazolidine derivatives) with E85.58 (Accidental poisoning by other specified drugs acting on central and autonomic nervous systems).

Choice Flag Can Be a Challenge

Finally, in the Choice column or 5th digit, you'll see 0 meaning off or digits 1-9 meaning, "In a combination entry, this is a list of one or more codes in the target system from which one code must be chosen to satisfy the equivalent meaning of a code in the source system."

Source: General Equivalence Mappings: Documentation for Technical Users (download at http://www.cdc.gov/nchs/icd/icd10cm.htm)

Here's our previous example:

62130 N8500 00000

Because the last digit is a "0," this means the choice column is off.

On the other hand, look at this backwards mapping example:

R6521 99592 10111

R6521 78552 10112

The last digits here are 1 and 2. This means that ICD-10-CM code R65.21 (Severe sepsis with septic shock) matches to both 995.92 (Severe sepsis) and 785.52 (Septic shock). The ICD-10-CM code combines them both.

What Should You Do With This GEMs Knowledge?

You might be reading through the GEMs flags and thinking, this is a very cumbersome process. Software folks are doing it, so you may think you don't have to learn about GEMs. But you may have to verify your software for accuracy and find inconsistencies.

Action step: Start with the top 25. Pull the most common diagnoses you use in your office, and look into your system to see if they map correctly from ICD-9-CM to ICD-10-CM. Then you can get your vendor to correct them.

Remember, inaccurate coding will result in increased denials and delayed payments.

This was a broad overview of GEMs. If you want to learn more, download this PDF: "General Equivalence Mappings: Documentation for Technical Users" at http://www.cdc.gov/nchs/icd/icd10cm.htm.