How to code a screening test vs. a monitoring test (and why it matters)

Patients who come in for an annual physical exam often expect that all the labs ordered for the visit, or at the visit, will be considered preventive and paid in full by their insurer. Some patients are surprised to later receive a bill for a diagnostic service.

Some diagnostic tests are considered preventive services, such as a screening colonoscopy or mammogram. But lab tests ordered to monitor a patient’s existing condition are not considered screenings. The correct diagnosis code for a test for monitoring or assessing a known condition is the code for the condition being monitored.

The ICD-10 definition of a screening is “the testing for disease or disease precursors in seemingly well individuals so that early detection and treatment can be provided for those who test positive for the disease (e.g., screening mammogram).” Some screenings, such as screening for lipoid disorders, have a specific ICD-10 code. Many of these are found in category Z13, "Encounter for screening for other diseases and disorders." There are also specific codes for screening for malignant neoplasms in category Z12 and for infectious diseases in category Z11.

Let’s use hyperlipidemia as an example. For a patient with no known history of hyperlipidemia who is being screened for the disease, you would use diagnosis code Z13.220, "Encounter for screening for lipoid disorders." For a patient already diagnosed with hyperlipidemia who is undergoing a lab test and being monitored or treated, you would use a code from category E78, "Disorders of lipoprotein metabolism and other lipidemias."

It isn’t easy to explain to a patient that not all labs done at the time of an annual physical exam are part of a preventive service. But you should feel confident that, according to ICD-10 rules, monitoring a known condition is not considered a screening.

– Betsy Nicoletti, a Massachusetts-based coding and billing consultant