2.03: ICD-9 & ICD-9-CM Codes

ICD-9-CM codes are still the main way of coding providers’ diagnoses in the United States. In this course, we’ll teach you what an ICD-9-CM code is, what it looks like, and how the ICD-9-CM code manual is organized.

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2.03: ICD-9 & ICD-9-CM Codes

History of How It Was Used

This code was initially intended for epidemiological purposes, but has since become an integral part of the reimbursement cycle. While ICD codes are still used to track the incidence and spread of diseases and injury, their most important facet today is demonstrating medical necessity in claims. In other words, ICD codes explain to the insurance payer why the doctor performed a certain procedure.

The code that’s currently in use in the United States is the Ninth Revision, Clinical Modification, or ICD-9-CM. ICD-9, the code set on which ICD-9-CM is based, was published in 1978. It was adapted for use in the United States in the same year. Note that ICD-9-CM is used only in the United States.

Initially ICD codes were to be updated every ten years, although the difficulty in updating these code sets in a timely manner led officials at the WHO to push this deadline back somewhat. Even with a more expanded revision schedule, the United States is far behind the rest of the world when it comes to ICD codes.

This outdated code set is problematic for coders and the healthcare industry at large, but the difficulty in overhauling the system to use the next code set, ICD-10-CM, is large enough that the United States has delayed it by over a decade. Canada, for example, has been using a version of ICD-10, the next revision of ICD, since 2000. We’ll cover the transition from ICD-9-CM to ICD-10-CM, and the reasons for this transfer, later.

What It Looks Like

When using ICD-9-CM codes, it’s imperative to code to the highest level of specificity. That’s an important phrase that you’ll probably hear over and over again during this course, and it means that you should always get down to the finest grain of detail. But what does that mean for ICD-9-CM codes? The answer lies in the makeup of the codes themselves.

ICD-9-CM codes are three-to-five digit numeric and, in certain cases, alphanumeric codes. The first three digits in a code are called the “category.” The category describes the general illness, injury, or condition of the patient. In many cases, the category is not specific enough to describe the full extent of the patient’s condition. Take dementia, for example. The basic ICD-9-CM code for dementia is 290. These first three numbers are the category, but since dementia is such a complicated condition, you would almost never stop coding at this level.

In cases where more specificity is needed, a decimal point is added after the category and one or two more digits are added. The fourth digit of the ICD-9 code is called the “subcategory,” and the fifth digit is called the “subclassification.” The subcategory describes the etiology (cause), site, or manifestation of the disease or condition. The subdivision provides even more information about the site, cause or manifestation of a disease, and is used only when the subcategory cannot provide sufficient information. Here’s the framework:

“123 – {Disease} (The first three digits make up the category)

  • 123.0 – {Disease} in Chest (The zero after the decimal point is the subcategory. It relates an important designation about the disease.)
    • 123.00 -… uncomplicated
    • 123.01 – … with complications in cardiac system
    • 123.02 – … with complications in digestive system (the last digit is the subclassification. This gives even further information about the designation outlined in the subcategory. If we were to select 123.02 as our code, we’d read the full code as “{Disease} in chest, with complications in the digestive system.”
  • 123.0 – Disease in legs
  • And so on…”

Now that we’ve got a loose idea of what the code “trees” look like, let’s return to our dementia example. The doctor’s report states our patient suffers from dementia and depression brought on by a series of strokes. Our patient is about 35, so not an elderly person. That’s an important distinction, as dementia is a condition that frequently occurs in patients over 65 years of age.

To code this accurately, we’d look at the category 290, for dementia, and then look at the various subcategories available listed below the category and rule out the codes for senile or presenile dementia, which removes codes 290.0, 290.1, 290.2, and 290.3. 290.4, however, is the code for vascular dementia, which is dementia brought on by reduced blood flow to the brain. That’s the code we’re looking for.

But our imperative to code to the highest level of specificity prevents us from stopping there. If you look at the subdivisions of 290.4, you’ll find four additional digits, each corresponding to an aspect of our patient’s condition. If the patient’s vascular dementia is uncomplicated, you would add the subdivision ‘0’ after 290.4, creating 290.40, for “vascular dementia, uncomplicated.”

If, however, the patient suffers from delusions in addition to their dementia, we’d code their condition as 290.42—vascular dementia with delusions. Let’s look at the code now. We’ve bolded the category, subcategory, and subclassification we used in this example.

“290 – Dementias

  • 290.0 – Senile dementia, uncomplicated
  • 290.1 – Presenile dementia
  • 290.2 – Senile dementia with delusional or depressive features
  • 290.3 – Senile dementia with depressive features
  • 290.4 – Vascular dementia
    • 290.40 – … uncomplicated
    • 290.41 – … with delirium
    • 290.42 – … with delusions
    • 290.43 – … with depressed mood”

As you may be able to tell from the example above, many ICD-9-CM codes branch down into more and more specific levels. If a category has a number of subcategories, these subcategories are indented below the main category. The subclassifications specific to each subcategory are then indented below their respective subcategory.

Most ICD-9-CM codes also make use of guidelines, or conventions, which help guide the coder to the correct code for the diagnosis. These conventions may be punctuation or verbal instructions.

Remember the difference between a “condition”—the state of the disease—and the “manifestation”—how the disease shows up. This is an important distinction in ICD-9-CM, as many symptoms or diseases are actually manifestations of an underlying condition. The condition of diabetes, for instance, has a number of different manifestations. Check out the table on Conventions in ICD-9-CM codes in the ebook.

Conventions in ICD-9-CM codes

Convention Meaning
Brackets [] Enclose synonyms, alternative wordings, or explanatory phrases. Also used to identify manifestation codes
Parenthesis () Enclose supplementary words, whether absent or present, that nonetheless do not affect the code of the disease
“Excludes” Terms, conditions, or manifestations listed under an “Excludes” are coded elsewhere. In some cases, these “excluded” terms may not be coded with the code they are listed under.
“Includes” Comes immediately after the three-digit code. Further defines or gives examples of the term listed in the category
“See” Indicates that another term or code should be referenced instead of the listed code
“See Also” Indicates that another term or code may prove useful in the coding process. Unlike “See,” “See Also” is not mandatory.
“Code First” Indicates that the coder should list a particular code first. This typically happens with an underlying condition that has multiple manifestations, like diabetes. In situations like this, the underlying conditions is coded first, and then the manifestation is coded. “Code first” codes typically appear in the manifestation codes.
“Use Additional Code” This phrase usually appears under the condition code (again, we’ll use diabetes), and informs the coder that other codes for manifestations are available.
“In Diseases Elsewhere Classified” This note is attached exclusively to manifestation codes. It means that this manifestation is directly related to an underlying condition. A code with this note attached to it can never be used as the primary code (it could never have a “code first” note).
“Not Elsewhere Classified” Abbreviated as “NEC,” you may find this attached to a disease or condition that is not classified in the code manual. Think of this as an unspecified code. An example of this might be category 995: “Certain adverse effects not elsewhere classified,” which includes “anaphylactic reaction due to unspecified food” and other catch-all terms.
“Not Otherwise Specified” Abbreviated as “NOS,” you’d turn to this in cases where the doctor or reporting physician has not provided

As you can see from the abbreviations NEC and NOS, the ICD-9-CM code set takes into account it’s limitations. There are a number of unlisted or nonspecific codes for diagnoses that don’t ‘fit’ exactly with the medical report. Coders use these as a last resort when they can’t find the exact code they’re looking for. This is something we’ll return to in Course 2-5 when we talk about the newer ICD-10-CM code set, which is set to replace ICD-9-CM in 2015.

How It Is Organized

Now that we know a little bit more about ICD-9-CM, let’s look at how the code set is organized. ICD-9-CM is divided into three volumes, but coders generally use the first two.

The first volume is the tabular volume, which lists disease descriptions and their corresponding codes. This section is divided into 17 chapters with two alphanumeric additions, called E-codes and V-codes. Each of these chapters contains a certain field of disease, and is confined to a certain numerical range.

The seventeen chapters, the diseases or maladies they cover, and their respective ranges, are listed in the table below. The numbers listed in the “Numerical Range” column are the categories for the ICD-9-CM codes. Bear in mind as well that the term “Chapter” is more of an official, organizational designation. You’ll usually find codes by their numerical range, and you won’t necessarily refer to a code as a “Chapter 1 code,” so much as a “code for infectious and parasitic disease.” For example:

Chapter Topic Numerical Range
1 Infectious and parasitic diseases 001-139
2 Neoplasms 140-239
3 Endocrine, nutritional and metabolic diseases, and immunity disorders 240-279
4 Diseases of the blood and blood-forming organs 280-289
5 Mental disorders 290-319
6 Diseases of the nervous system 320-359
7 Diseases of the sense organs 360-389
8 Diseases of the circulatory system 390-459
9 Diseases of the respiratory system 460-519
10 Diseases of the digestive system 520-579
11 Diseases of the genitourinary system 580-629
12 Complications of pregnancy, childbirth, and puerperium 630-679
13 Diseases of the skin and subcutaneous tissue 680-709
14 Diseases of the musculoskeletal system and connective tissue 710-739
15 Congenital anomalies 740-759
16 Certain conditions originating in the perinatal period 760-779
17 Injury and poisoning 800-999
E-codes External causes of injury e800-e999
V-codes Supplementary classification of factors influencing health status and contact with health services v01-v91

For a full list of the chapters and topics be sure to download the ebook. As you can see, these divisions are relatively self-explanatory. If you were trying to code measles, for example, you’d look at the section of codes corresponding to “diseases of the skin and subcutaneous tissue,” in Chapter 13. Likewise, if you were going to code a diagnosis of hypertension, you’d look in the section for cardiovascular diseases.

E-codes and V-codes are where it gets slightly more complicated. Note that codes 800-999 correspond to injury and poisoning, while the E-codes correspond to “external causes of injury.” This might seem redundant, but injury codes actually correspond to the specific type and location of injury, as opposed to the external cause of the injury. One example of an injury code is 800.01—a “closed fracture of the vault of the skull with no loss of consciousness.”

In injury codes, subcategories and subclassifications are very important. A phrase like “fracture of the vault of the skull” doesn’t tell us the whole story about the diagnosis. For instance, what kind of fracture is it? Is it open or closed? Did the patient suffer any brain-related injuries? Internal bleeding? Did the patient lose consciousness? The subcategories and subclassifications provide all of this important additional information.

So, injury codes describe the injury itself. E-codes, on the other hand, describe the cause of the injury. E-codes can be important for insurance purposes, and they’re also extremely useful when coding for trauma centers and emergency rooms. The cause of an injury, whether it’s an automobile accident, a gunshot, or a fall from a ladder, can inform the billing process and help doctors get a better picture of what happened to the patient. Some E-codes include e893, “accident caused by ignition of clothing” and e813, “motor vehicle accident involving collision with other vehicle.”

There are hundreds of E-codes, each attached to seemingly every type of injury. E-codes also utilize subcategories and subclassifications to get to the highest level of specificity.

V-codes describe reasons that people might visit a healthcare provider outside of immediate injury or disease. There are V-codes for childbirth, screenings for hereditary diseases or congenital abnormalities, or persons at risk from exposure to communicable diseases. In other words, if there is a reason a person in good health visits a healthcare provider, you can use a V-code.

We’ll cover more about ICD codes in the next course.

Second Section: Alphabetic index

The next volume of the ICD code manual is the alphabetic index. Coders use this index to locate codes in the tabular section. You can use the alphabetic index like you would any index. Simply search for a general term and the index will point you to any of the applicable codes.

The index also redirects coders to more accurate sections of the code set.
This index is especially helpful if you don’t know the medical term for the condition or illness you’re coding. For instance, there’s an index entry for “cocked-up toe” (known medically as hallux rigidus). You won’t find anything that colloquial in the tabular section.

Essentially, the alphabetic index gives us directions around the tabular volume. It’s important to code from the tabular section, however. We use the alphabetic index in order to track down codes, but we always confirm in the tabular section.

Third Section: Alphabetic and tabular index of procedures used by hospitals

The third and final section of the ICD-9-CM manual consists of procedure codes used by hospitals to report services and procedures performed in their facilities. We will not be covering this volume in depth in this course, as physicians and coding professionals do not use it to report codes.

Now that we’re familiar with what an ICD-9-CM code looks like and how it’s organized in the code manual, it’s time to look closer at how to use these codes. In the next course, we’ll show you how to use ICD-9-CM and give you more examples of the code in action. In the sections following that, we’ll talk about the new ICD code set, ICD-10-CM, that is set to replace ICD-9-CM.

Video: ICD-9 & ICD-9-CM Codes

ICD-9-CM codes are still the main way of coding providers’ diagnoses in the United States. In this video, we’ll teach you what an ICD-9-CM code is, what it looks like, and how the ICD-9-CM code manual is organized.