Oncology & Hematology Coding Alert

Question: If a patient comes in for medication refills for a chronic condition, and the provider orders labs, is it okay to use Z00.00 as a diagnosis code if it is not the primary diagnosis and the chronic condition diagnosis is listed first? My understanding is that Z00.00 can only be used when it is a well/preventive visit. If we remove Z00.00 from the claim, we do not have a code to cover the routine labs.

AAPC Forum Participant

Answer: Even though the ICD-10-CM Alphabetic Index entry for Encounter - laboratory (as part of a general medical examination) directs you to Z00.00 (Encounter for general adult medical examination without abnormal findings), that does not mean it is the best code for you to use in this situation for a number of reasons.

First, as the Alphabetic Index entry suggests, Z00.00 describes an encounter where the provider performed a general examination on the patient, which is why the code is generally accepted as the code for a physical exam for an adult presenting without a specific complaint or problem. The code is also used specifically for encounters where the exam finds no abnormal findings, which means you would not use it for a patient with a chronic condition.

Next, you would not use Z00.00 because your provider ordered labs for the patient for some reason, which would point to codes from Z79.- (Long term (current) drug therapy), and most likely a code from Z79.63- (Long term (current) use of chemotherapeutic agent), which enables you to code for the specific drug your provider is administering. This is reinforced by ICD-10-CM guideline I.C.21.3, which directs you to “assign a code from Z79 if the patient is receiving a medication … as treatment of … a disease requiring a lengthy course of treatment (such as cancer).”

Another possibility might be Z76.0 (Encounter for issue of repeat prescription), which you would use if the patient did not receive an evaluation and management (E/M) service from your provider during the encounter and was simply picking up the medication prescription.

Remember: Neither Z76.0 nor the Z79.- codes may be principal or first-listed diagnosis codes, per ICD-10-CM guideline I.C.21.c.16. So, as you point out, you will need to list the diagnosis code for the patient’s condition as the principal diagnosis for the encounter.

Additionally, remember that the Z79.- codes have a Code also instruction to use Z51.81 (Encounter for therapeutic drug level monitoring) as appropriate.

Finally, guideline I.C.21.3 goes on to tell you not to “assign a code from category Z79 for medication being administered for a brief period of time to treat an acute illness or injury (such as a course of antibiotics to treat acute bronchitis).”