California Subscriber
Answer: Code 42700 (incision and drainage abscess; peritonsillar), 42720 ( retropharyngeal or parapharyngeal, intraoral approach) and 42725 ( external approach) are indeed specific to cases of PTA. However, as all procedures should be coded to the highest level of specificity, the situation you describe should be coded with 88170 (fine needle aspiration; superficial tissue [e.g., thyroid, breast, prostate]).
In fact, needle aspiration is a definitive drainage procedure for PTA. Aspiration can also be used to confirm the presence of pus prior to incision and drainage, as was the first step in your question.
Make sure you also bill for any anesthetic used, and include the diagnosis code for PTA, 475.