Medicare Broadens Coverage for Prothrombin Time
Published on Tue Jan 01, 2002
Medicare recently announced that it would begin a national coverage policy for home prothrombin time (PT) testing for patients with mechanical heart valves. This policy enlarges the wide range of conditions that are covered for PT tests, which evaluate a patient's blood-clotting ability.
The PT test can be used in several settings such as laboratories, physician offices, and homes. Several coverage issues affect reimbursement for this test, including where and how the sample is taken and evaluated, how frequently the test is given, and who oversees the procedure. Appropriate diagnosis coding to establish medical necessity is also crucial for payment. Related coagulation tests might also be ordered, and these should be reported separately.
Coagulation Tests
Coagulation is caused by many reactions involving various factors in the blood. Two converging pathways can result in clot formation: the extrinsic pathway, which is initiated by tissue damage and assessed using PT (85610, prothrombin time), and the intrinsic pathway, which is assessed using PTT (CPT 85730 , thromboplastin time, partial [PTT]; plasma or whole blood). These two tests are commonly used to determine the efficacy of blood-thinning medications based on how long it takes the blood to clot.
"PT is often used to assess the drug warfarin (Coumadin). PTT is frequently used to assess the drug heparin," says Barb Miller, MT (ASCP) SH, clinical lab specialist with Nebraska Health System in Omaha. The PT test results are expressed in seconds and/or as an international normalized ratio (INR). Because commercial thromboplastin reagents used in the laboratory PT test have different potencies, the INR reporting method was developed. The INR is the PT ratio that would result if the World Health Organization reference thromboplastin were used in performing the test. Because INR is a calculation, it is not paid in addition to the PT, but is part of the service described by 85610.
In addition to the traditional laboratory methods, PT testing is available through the use of several simplified, automated devices. These PT systems are becoming more common for point-of-care testing. They generally involve direct blood collection through a finger stick into a cuvette containing premeasured reagents. The determination of PT seconds and INR is automatically calculated and recorded in the instrument.
Aside from monitoring anticoagulation therapy, other related laboratory tests are used for diagnostic investigations of the patient's hemostatic status. For example, abnormal PT and/or PTT tests may indicate that a patient has a deficiency of one or more coagulation factors. Following these test results, a physician may order a diluted PT (85611, prothrombin time; substitution, plasma fractions, each) or diluted PTT (85732, thromboplastin time, partial [PTT]; substitution, plasma fractions, each). "Essentially, these tests repeat the PT or PTT on a mixture of the patient's [...]
