Primary Care Coding Alert

Question: I have not been coding for very long, and I have a question about burn diagnosis coding. What exactly is the -Rule of Nines- and how should I use it?

Kentucky Subscriber

Answer: The -Rule of Nines,- which you-ll apply to your burn diagnosis coding, is a breakdown of the patient's total body surface area (TBSA). Physicians use the Rule of Nines to report what percentage of the patient's body suffered burns.

Coders use this information to arrive at the appropriate fourth digit for codes from the 948.xx series (Burns classified according to extent of body surface involved).

These are the TBSA breakdowns in CPT 2007:

• Head and neck (collectively), right arm, and left arm each equal 9 percent of TBSA. So if the patient's left arm was burned, the Rule of Nines states that TBSA burned is 9 percent.
• Back trunk, front trunk, left leg, and right leg each account for 18 percent of TBSA. (You can divide the front and back trunk into upper and lower portions equaling 9 percent each. Further, you can also divide each leg into front and back, with each segment equaling 9 percent.)
• Genitalia equal 1 percent of TBSA.

Consider this example: A patient who dropped a pot of boiling water suffered second-degree burns to the bottom portion of her front trunk and genitalia. The patient had no third-degree burns. In this scenario, the front-trunk burns constitute 9 percent TBSA, and the burn to the genitalia represents 1 percent TBSA; this equals 10 percent TBSA

Note: To choose the most accurate 948.xx code, you must also know the TBSA of the patient's third-degree burn areas, because the fifth digit of 948.xx represents the percentage of third-degree burns the patient had.

So the patient in the above example had second-degree burns to 10 percent of TBSA, with no mention of third-degree burns. Based on the information in the example, you should report 948.10 ( ... burn [any degree] involving 10-19 percent of body surface; less than 10 percent or unspecified).

Remember: In addition to the 948.xx burn code, you-ll also need to include ICD-9 codes to reflect the locations of the burns. Coders can find these ICD-9 codes in the 941-947 series.

Also: The above Rule of Nines explanation does not apply to children with burns. For children, the Rule of Nines breaks down thusly:

• Head equals 18 percent of TBSA.
• Chest and abdomen equal 18 percent of TBSA.
• Back equals 18 percent of TBSA
• Right and left arm each equal 9 percent of TBSA.
• Right and left leg each equal 14 percent of TBSA.

Answers to You Be the Coder and Reader Questions reviewed by Kent J. Moore, manager of Health Care Financing and Delivery Systems for the American Academy of Family Physicians in Leawood, Kan.