Pathology/Lab Coding Alert

Question: As a lab coder, we use the diagnosis assigned by the ordering physician when submitting claims. We perform lots of Pap tests and I’ve noticed that we sometimes get Z codes as the ordering diagnosis. Is that acceptable for Pap or other lab tests?

Nebraska Subscriber

Answer: Yes, it is appropriate in some cases to bill certain lab tests, including Pap tests, with a Z code as a primary diagnosis.

For instance: When your lab performs a test for a “well” individual to screen for early detection of disease, the ordering physician may use a Z code to describe the reason for the test. Also, if the lab performs testing to monitor patient treatment or condition, the ordering physician may use a Z code as the primary diagnosis in some cases.

Guidance: “Z codes are for use in any healthcare setting. Z codes may be used as either a first-listed (principal diagnosis code in the inpatient setting) or secondary code, depending on the circumstances of the encounter. Certain Z codes may only be used as first-listed or principal diagnosis,” say the Centers for Medicare & Medicaid Services (CMS) in their guideline sheet “ICD-10-CM Official Guidelines for Coding and Reporting FY 2024.”

Examples: The following situations may warrant reporting a Z code as the primary diagnosis for a lab test:

• For an annual prostate-specific antigen (PSA) test for a patient with a history of prostate cancer, use Z85.46 (Personal history of malignant neoplasm of prostate)
• For a kidney function test for a patient taking Celebrex for arthritis, use Z51.81 (Encounter for therapeutic drug level monitoring) and Z79.1 (Long term (current) use of non-steroidal anti-inflammatories (NSAID))
• For an annual screening Pap test for a patient with no signs or symptoms and no history of positive Pap tests or disease, use Z12.4 (Encounter for screening pap smear for malignant neoplasm of cervix)
• For a human papilloma virus (HPV) screening at an appropriate time interval, use Z11.51 (Encounter for screening for human papillomavirus (HPV))

Bottom line: Chapter 21 of ICD-10-CM, which contains the Z codes, is titled “Factors influencing health status and contact with health services (Z00-Z99).” Physicians use Z codes to help provide a comprehensive description of a patient’s condition and actions taken in an encounter. But this documentation also serves to indicate medical necessity for those actions, such as lab testing, and thus, support reimbursement.

Ellen Garver, BS, BA