Pathology/Lab Coding Alert

Question: Which ICD-9 code(s) should we use when billing for a PT test to monitor Coumadin therapy? I read in a past issue of your newsletter [Vol. 10, No. 5] that you should list V58.61 first, not the underlying condition. But ICD-9 lists V58.61 as a secondary diagnosis -- what should we do?

New York Subscriber

Answer: You are correct that ICD-9 lists V58.61 (Long-term [current] use of anticoagulants) as a secondary diagnosis. However, the article you referenced correctly states that you shouldn't list first the underlying condition when the reason for the prothrombin time (PT) test is to monitor the effectiveness of anticoagulation medication.

A change to the laboratory national coverage determination (NCD) for PT now lists V58.83 (Encounter for  therapeutic drug monitoring) as a covered diagnosis. ICD-9 instruction for that code states, "Use additional code for any associated long-term (current) drug use (V58.61- V58.69)."

If the reason for the PT test is to monitor the effectiveness of anticoagulation medication, the diagnosis coding for the service should be V58.83, followed by V58.61. You may also list an additional code for the underlying condition, such as atrial fibrillation (427.31).

Get procedure right: Code the PT test as 85610  (Prothrombin time). Don't forget to add modifier QW (CLIA waived test) if your lab operates with a certificate of waiver under the Clinical Laboratory Improvement Amendments (CLIA).