ICD-10-CM Coding System

International Classification of Diseases, 10th Revision, Clinical Modification (ICD10-CM) codes indicate the condition, symptoms, problems, complaints, diagnosis or other reasons for the visit or procedure. In other words, ICD-10 codes justify the use of CPT® codes. You may list up to eight ICD-10 codes on the Medicare claim form, but the first one used must reflect the chief reason for the services provided. Enter only one diagnosis per detail line on the electronic or paper claim. The additional diagnoses are used to describe any co-existing conditions. The chief reason and the co-existing conditions must also be noted in the medical record. Co-existing conditions requiring specific tests or procedures should also be recorded on the claim form and in the medical record.

Billing the Highest Level of Specificity

ICD-10 codes are composed of three-, to seven-digit alphanumeric codes. ICD-10 codes classify groups of diseases and injuries by etiology and by organ system. These codes also classify symptoms.

Diagnosis codes must always be documented to the highest known level of specificity. If a three-digit code lists additional-digit codes as subcodes, then the three-digit code becomes a category, not a billable code.

Samples of ICD-10 Levels

Using ICD-9 Z Codes

This can arise in two main ways:

• When a person who may or may not be sick encounters the health servies for some specific purpose, such as to receive limited care or service for a current condition, to donate an organ or tissue, to receive prophylactic vaccination (immunization), or to discuss a problem with is in itself not a disease or injury.
• When some circumstance or problem is present which influences the person's health status but is not in itself a current illness or injury.

ICD-10 Z Codes

How to Identify the Correct ICD-10-CM Diagnosis Code

Refer to the most current ICD-10-CM Codebook:

• Step 1) Review the Convention for ICD-10-CM and the General Coding Guidelines in the Official Guidelines for Coding and Reporting; Step 2) Use the crosswalk to identify the ICD-9-CM code and the corresponding ICD-10-CM code;
• Step 3) Verify the main term in the Volume 1 Alphabetic Index;
• Step 4) Verify the code in the Volume 2 Tabular List;
• Step 5) Read all of the inclusion, exclusion notes, use additional codes, code first underlying disease instructions, code also, 4th, 5th and 6th character requirements and 7th character extension requirements;
• Step 6) Consult the official ICD-10-CM guidelines for the specific codes identified; and Step 7) Confirm and assign correct code.