ICD-9 Coding Overview

ICD-9 (International Classification of Diseases 9^th Revision) codes are diagnosis and status codes. These tell why the patient went to the doctor’s office. There are three main types of diagnosis codes. They are:

Numeric codes (000-999.99) which are used for problems, illnesses or injuries

V codes are used to indicate a status such as pregnancy, exposure to an illness (that the patient has no symptoms of contracting but needs checking), high-risk behavior, or a significant medical history or family history. You can see that these are not sicknesses but need to be checked on by a doctor

E codes are external causes. An external cause is the reason behind an illness or injury. An example would be a diagnosis (numeric code) indicating a cut (laceration) on the forehead, the E code would tell us how it happened for example a car accident. Since E codes are used to explain another diagnosis they cannot be the first diagnosis and they cannot be used alone.

ICD-9 coding is very simple, but requires accuracy. Assigning an incorrect diagnosis to a patient can label the patient with a disease that they don’t really have. Mislabeling can result in problems for the patient getting life insurance or health insurance coverage.

Although this report’s purpose is not to prepare you for a coding certification, a brief description on reading the ICD-9 book is in order. I highly recommend that the reader study coding prior to trying to do any coding.

The ICD-9 book is divided in to two. The first section at the front of the book is an alphabetical listing of diagnosis words. The second section is the numeric listing of the diagnosis ordered by their assigned code. In order to select the correct code you must first look up the words in the alphabetical listing then reference the numeric listing for the actual, full code description and additional code details.

If you have an ICD-9, open it up and look in the alphabetical index for the word diabetes. You should find a reference to the 250 section of the numeric section. Now refer to the numeric listing for the 250 codes. There are a lot of diabetes codes for one single disease! Look at the codes you will see most of them have two digits after a period making the diabetes codes 5 numbers (250.XX). The additional digits after the period explain the condition further. Read the descriptions to get an idea of what I mean. 

Now look at the code 250 (no additional digits), notice that there is a little (4) next to the code, this indicates that a 4^th digit is required. Notice next that the code 250.0 has a little (5) next to it, this means that it needs a 5^th digit. The code 250 is a disease classification for diabetes, the 4^th digit is the sub-classification indicating the type of diabetes (juvenile or adult onset a.k.a. type 1 or type II) and the 5^th digit tells you of any manifestations or problems resulting from the disease.

In billing it is imperative to complete the diagnosis code to the highest level of specificity meaning use all possible digits as indicated by the presents of the little 4 or 5 if applicable. Now look up the code 496 in the numeric listing, note that there is no little 4 or 5. Code 496 is fully specific without any more digits. The example of code 496 is to show you that not all codes need additional digits but if there is a little 4 or 5 you must code using those digits.

Q. So what happens if you do not use the additional digits?

A. The medical bill (claim) will not pay and the insurance rejection will say something about the code not being specific enough or truncated. Truncated means shortened or reduced.

Q. But what if you don’t know the additional details about the condition that are required to choose a more specific code?

A. You have two options. First you can ask the provider to be more specific, show the provider the ICD-9 book and ask them to clarify based on your options. Second option is NOS or NEC. NOS means not otherwise specified by the doctor and NEC means not elsewhere classified within ICD-9. These can be used to indicate that missing information. It is often indicated by the presents of a 0 or a 9 as the final digit after the period in a code. Be careful though, because NOS codes are not always acceptable for an insurance to consider payment on a claim.

Q. What if the options for the extended digits don’t have the sub-classification or manifestation that I need to report the condition?

A. After you have double checked that the correct digit does not exist and verified it with the provider you may opt to use an NEC code. NEC means not elsewhere classified.

ICD-9 coding hints

• Most importantly in ICD-9 coding, you must read. There are very important notes and rules associated with codes that must be followed. Some codes cannot be used alone, or without another code and some code descriptions will appear similar on initial review. Take careful note of the sub-classifications, manifestations and conditions that are included and excluded from a particular code.
• Never code or bill using diagnosis that the provider describes as “possible”, “probable” or “rule out”. Only use the conditions, diseases or symptoms that are confirmed.
• Do not use an “E” code as a primary diagnosis (the first one)
•  Be sure that the diagnosis justifies the procedure performed (this is called medical necessity and we will talk more on this later).