I would use an abnormal finding code for a diagnosis of elevated PT/INR along with the V code to indicate long-term use of the Coumadin.
The term anticoagulation is not a codeable diagnostic statement. Clarification needs to be sought as for the reason for the test. Most likely, the test is simply to check the levels of PR/PTT/etc. and if so, then the codes should be V58.83 along with the V code for long-term use of the anticoagulant.
Independent Coding & Education Consultant