Watch the diagnosis -- you may be surprised at the first-listed code. 1. Put Proper Code to Periodic PT Test "Physicians often use PT [prothrombin time] to assess patient response to the drug warfarin," says Barb Miller, MT (ASCP) SH, with Nebraska Medical Center. When patients on warfarin therapy come to your "Coumadin clinic" for periodic testing to assess their anticoagulation status, you should report 85610 (Prothrombin time) for the test. Remember the modifier: If the nurse needs to evaluate new symptoms such as bruising or bleeding -- something beyond the basic PT visit -- code 99211 (Office or other outpatient visit for the evaluation and management of an established patient, that may not require the presence of a physician ...) may be appropriate also. Remember: to be payable codes under the physician fee schedule. 2. Pull Out V58.61 for Diagnosis Do this: "If the reason for the PT test is to monitor the effectiveness of anticoagulation medication, the primary diagnosis code for the service should be V58.61 (Longterm [current] use of anticoagulants)," Slagle says. You may report the underlying reason for the warfarin therapy, such as a personal history of blood diseases (V12.3), as a secondary diagnosis. For a complete list of payable diagnoses, see the Medicare National Coverage Determination (NCD) for PT on the Internet at www.cms.hhs.gov/CoverageGenInfo/downloads/manual200901.pdf. 3. Let Necessity Guide Frequency Changes in the underlying medical condition or warfarin dosing determine the need for repeat PT tests, so CMS does not establish an across-the-board frequency limitation for this. On the other hand: