Pathology/Lab Coding Alert

Don't skip this modifier - or you can expect claims denials.

Monitoring PT/INR for patients on anticoagulation therapy is fraught with coverage and coding pitfalls that will make your head spin.

Let our experts be your guide to understand the Prothrombin Time (PT) test, International Normalized Ratio (INR) reporting, and the various services that labs and physicians may provide associated with this testing.

Tip 1: Know the Test

PT is a test used to evaluate the extrinsic pathway clotting factors, often to monitor the dosing and therapeutic effectiveness of warfarin (brand name Coumadin) in coagulation control. Warfarin helps reduce clotting by impairing the effect of vitamin K in the liver, effectively reducing production of extrinsic pathway factors.

The CPT^® code for the PT lab test is 85610 (Prothrombin time). The lab analyst performs the test by mixing reagents with the patient blood sample and noting the time when the plasma clots. When performed for a patient taking warfarin, the clotting time indicates the effectiveness of the medication at the current dosage. Labs express PT test results in seconds and/or as an INR number.

Here's why: Commercial thromboplastin reagents used in laboratory PT tests have different potencies, so the INR reporting method "normalizes" results by reporting the PT ratio that would result if the World Health Organization reference thromboplastin were used to perform the test.

Because PT is such a common test for monitoring warfarin therapy, as well as for other medical indications, many payers have policies concerning coverage rules, testing frequency, coding requirements, and more.

Tip 2: Master Lab Test Coverage Rules

Medicare provides a National Coverage Determination (NCD 190.17, Prothrombin Time) for lab PT testing, and other payers follow these or similar guidelines. The NCD provides the following indications for the test:

• to assess patients taking warfarin, but not other anticoagulants such as heparin
• to assess patients with signs or symptoms of abnormal bleeding or thrombosis, such as abnormal bruising, swelling, or petechiae
• to evaluate patients who have a history associated with the risk of bleeding related to the extrinsic pathway, such as liver dysfunction, dysfibrino­genemia, lupus erythematosus, vitamin K deficiency, and many others listed in the policy
• to evaluate patients with signs or history of bleeding or thrombotic abnormality who are scheduled for a medical intervention associated with increased risk of bleeding or thrombosis.

You can find a complete list of covered ICD-10 codesbydownloading the most up-to-date file at www.cms.gov/Medicare/Coverage/CoverageGenInfo/LabNCDsICD10.html.

Caution: If the primary reason for the PT test is to monitor the effectiveness of anticoagulation medication, the first-listed diagnosis code should be Z79.01 (Long term [current] use of anticoagulants). You should report a secondary diagnosis for the underlying reason for the warfarin therapy, says Peggy Slagle, CPC, coding and compliance manager for the department of pathology/microbiology at the University of Nebraska Medical Center in Omaha. For instance, you might list mechanical heart valve (Z95.2, Presence of prosthetic heart valve) or atrial fibrillation (such as I48.91, Unspecified atrial fibrillation) as the secondary diagnosis.

Frequency: The NCD also outlines some expectations about how often the test is covered, such as the following:

• weekly for patients on End Stage Renal Disease (ESRD) therapy without specific symptoms
• once every two to three weeks for patients on stable warfarin therapy
• when there is a change of medical status for patients with signs or symptoms of abnormal bleeding or thrombosis

Tip 3: Beware Certifications, Calculations, and More

Even if you abide by all the previously-mentioned coverage criteria, other issues can plague your PT test payment if you don't take heed. Read on to make sure you avoid the following pitfalls:

CLIA certification: If your lab operates with a CLIA certificate of waiver, you'll need to append modifier QW (CLIA waived test) to 85610 if you want to get paid for the service.

Beware INR trap: If the physician orders an INR, your lab will still perform the PT test and report the results in seconds, but also calculate the INR based on the test results. "You should bill the core test that the lab performs, which is 85610," says William Dettwyler, MTAMT, president of Codus Medicus, a laboratory coding consulting firm in Salem, Ore. "You should not bill an additional code for the INR calculation."

Physician review: If a pathologist or other physician provides prolonged Coumadin monitoring in an outpatient setting, you might be able to bill for the service using one of the following codes:

• 99363 (Anticoagulant management for an outpatient taking warfarin, physician review and interpre­tation of International Normalized Ratio [INR] testing, patient instructions, dosage adjustment [as needed], and ordering of additional tests; initial 90 days of therapy [must include a minimum of 8 INR measurements])
• 99364 (... each subsequent 90 days of therapy [must include a minimum of 3 INR measurements]).

Medicare lists these codes with a "B" (Bundled code) code status, which means that payment for the item is included with payment for any physician service on the same day, such as an E/M service. You should find out your payers rules about these codes before billing them.

There's more: Some patients may follow a regimen of self-INR monitoring, which you'll learn more about in "Follow Home PT/INR Monitoring Rules" below. You can bill for PT lab testing even if the patient uses self-monitoring. The NCD for lab PT testing states, "Current medical information does not clarify the role of laboratory PT testing in patients who are self-monitoring. Therefore, the indications for testing apply regardless of whether or not the patient is also PT self-testing."