According to the ICD-9 CM official guidelines for coding and reporting, burns are classified by depth, extent and by agent (E code). So before you assign a diagnosis code, here are a few things to remember.
- Location/anatomic site of the burn
- Extent/severity of the burn
- Percentage of the body surface burnt
- Cause of the burn
Severity of the burn is determined by burned surface and the depth of the 
burn and this comes from the 941-946 series. Burn depths are classified in three degrees: first is superficial burns (inflammed and painful) involving the epidermis. These include erythema or redness of the skin; second degree invloves the middle layer i.e. dermal. These burns include blisters; third degree invloves full thickness skin loss. These are serious burns invloving all the layers of the skin including the fatty tissue beneath them.
Always sequence the first code that reflects the highest degree of burn (if more than one burn is present).
For example: A 25 yr old presents with a second degree burn of the right forearm and first degree burn of the right index finger and third degree burn of the abdomen. You must sequence your codes as 942.33 (3rd degree burn of the abdomen), 943.21 (2nd degree burn of the forearm), 944.11(1st degree burn of the index finger).
Note: You should only code for the highest level burn when you assign multiple burns of differing degrees (severity) in the same body area.
Next you need to assign the code that reflects the extent of the burn i.e. how much body surface area is involved and this code comes from the 948 category. The inclusion of codes from 948 series is important as it may affect your reimbursement. To assign a code from 948 series simply ask what percentage of the body has been burnt and what percentage of the body has received 3rd degree burns.
For example: A patient presents with a 10% body surface with third degree burn of the thigh, assign code 948.11. Here the fourth digit of the code indicates the total percentage of the body that has been burnt and the fifth digit indicates the percentage of the body that has received third degree burns.
Lastly you need to assign the E code. E codes suggests as how the burns occured, whether it was accidental or caused by a hot substance or objects. If the burn is accidental, report an E code from E890-E899 (accidents caused by fire and flames) and if occured from hot objects report the code from E924 (accidents caused by hot substance or objects, caustic or corrosive material and steam).
For example: accidental steam burn in factory should be reported as E924.0 (burn by steam), E849.3 (Industrial place and premises).
Case Study: A 24 yr old youngman presents with a third degree burn on the right forearm 2%; first degre burn on right wrist 3%; and second degree burn to the right chest wall 5%. He states that he got burnt by hot steam while working in a restaurant.
Here’s how the Codes should be sequenced:
943.31 (3rd degree burn forearm);
942.22 (2nd degree burn chest wall);
944.17 ( 1st degree burn wrist);
948.11 (Percent TBSA – indicates the percentage of body surface with 3rd degree burns);
E924.8 (accidents caused by hot substance or object, caustic or corrosive material & steam)
E849.6 (accident caused in Public building- restaurant).