Question: The FP scraped skin and prepared a KOH prep to look for infectious agents. How should we code this? Louisiana Subscriber Answer: The correct CPT code is 87220 (Tissue examination by KOH slide of samples from skin, hair, or nails for fungi or ectoparasite ova or mites [e.g., scabies]). When coding for a Medicare patient, the appropriate HCPCS code is Q0112 (All potassium hydroxide [KOH] preparations).