CMS Guidelines for Diagnostic Coding

In the March 4, 1994 Federal Register, the Centers for Medicare and Medicaid Services announced all claims for physician services under Medicare Part B must include proper ICD-9-CM diagnostic coding on the CMS-1500 (formerly known as HCFA) claim form. For physicians who accept payment in an assignment related basis, failure to do so may result in denial of payment.

The Centers for Medicare and Medicaid Services provides specific guidelines to aid in standardizing U.S. coding practices. The guidelines for outpatient facilities, physician offices, and ancillary care are summarized below:

1. Identify each service, procedure, or supply with an ICD-9-CM code to describe the diagnosis, symptom, complaint, condition, or problem.

2. Identify services or visits for circumstances other than disease or injury, such as follow-up care after chemotherapy, with V codes provided for this purpose.

3. Code the primary diagnosis first, followed by the secondary, tertiary, and so on. Code any coexisting conditions that affect the treatment of the patient for that visit or procedure as supplementary information. Do not code a diagnosis that is no longer applicable.

4. Code to the highest degree of specificity. Carry the numerical code to the fourth or fifth digit when available. Remember, there are only approximately 100 valid three-digit codes; all other ICD-9-CM codes require additional digits.

5. Code a chronic diagnosis when it is applicable to the patient's treatment.

6. When only ancillary services are provided, list the appropriate V code first and the problem second. For example, if a patient is receiving only ancillary therapeutic services, such as physical therapy, use the V code first, followed by the code for the condition.

7. When surgical procedures are performed, code the diagnosis applicable to the procedure. If, after the procedure has been done, the condition necessitating the surgery is more specifically identified, or even determined to be different than the preoperative diagnosis, code the most specific diagnosis determined to be the reason for the surgery.