Primary Care Coding Alert

Question: A patient came in to see our physician after being bitten by a tick. The patient’s mother had already removed the tick, but the mother brought the patient in for a follow-up. The provider saw the patient, then told her to return in two weeks for blood work. My questions are these: first, I know we should use W57.-, but is this encounter regarded as initial given that the patient’s mother has already treated the bite? Second, should I use Z20.818 for the encounter? And, last, do I need to use any other codes beside these?

Arizona Subscriber

Answer: Let’s address your questions in the order you ask them.

First, the encounter would be regarded as initial, simply because this is the first time the patient is being seen by a medical professional for the problem. So, per ICD-10 guidelines, you would use seventh character A with the nonvenomous insect bite code, leading to W57.XXXA (Bitten or stung by nonvenomous insect and other nonvenomous arthropods, initial encounter).

Second, you would not use Z20.818 (Contact with and (suspected) exposure to other bacterial communicable diseases) for this encounter, though you could use it once the patient returns. That’s because there’s no indication the patient had contact with, or suspected exposure to, a bacterial communicable disease, as evidenced by the fact the patient did not receive any treatment or work-up at this encounter. If the patient returns, and the provider orders the blood work, that would be the appropriate time to use this particular code.

Finally, you can use one other code in this encounter to reflect the anatomical site of the bite and add a sixth digit to indicate laterality as appropriate. You will also need to add a seventh digit, which, like the external cause code, will be A, as the encounter for the injury is also regarded as initial. So, if the patient’s bite was on the right forearm, you would use S50.861A (Insect bite (nonvenomous) of right forearm, initial encounter).