Register Login

PT/PTT Screening

Yesterday, 9-1-20, a colleague contacted George [me] because her physcian had ordered a PT and PTT as part of a pre-procedural workup. She asked what the PT/PTT accomplished, and both the physician and nurse practitioner offered no explanation. After considerable discussion, the PT/PTT order was canceled.

I recalled a similar situation from 2011 when my physician ordered a PT/PTT prior to a procedure. Unlike my colleague, I agreed to the assays, but later asked the physician if preliminary PT/PTT screening had ever turned up a “positive.” She said no, she just ordered the tests to avoid lawsuits.

There exists an authoritative collection of publications from the late 90s and early 00s all of which illustrate the poor predictive values for the bleeding time, PT, and PTT as screens meant to predict intra- or post-procedural bleeding. The bleeding time has no redeeming qualities and has long been obsolete, and the PT/PTT are effective only when there is an indication for a potential bleeding [or perhaps thrombotic] disorder. Nevertheless, physicians continue to order screens, perhaps bowing to history, peer pressure, or concern for litigation, arguing the assays are inexpensive and readily available. This issue is addressed in a Choosing Wisely recommendation from the American Society for Clinical Pathology [Click].

Recently, in an effort to expand ASCP’s Choosing Wisely recommendation, Brianna Miller, MS, MLS, University of Alabama at Birmingham and George have proposed the following Choosing Wisely recommendation, pinpointing the PT and PTT:

“Avoid routine prothrombin time (PT) and partial thromboplastin time (PTT, APTT) pre-operative screens on unselected patients.

Nine observational studies, including three prospective studies, reported the positive predictive values for hemostatic complications for the PT and PTT ranged from 0.03 to 0.22, whereas computed 95% confidence intervals for each assay generates a 2.5% positive rate from normal subjects. A review of 27,737 PT and PTT results over two decades showed that only 8% of PTs and PTTs were clinically indicated based on current or prior patient history of bleeding. A study of general hospital unregulated coagulation screening requests produced few abnormal results with no evidence that they were associated with an increased bleeding risk. In this study, all bleeding cases could be attributed to an underlying condition. The 1989 Medical Necessity Project of the Blue Cross and Blue Shield Association endorsed by the American College of Physicians found that at least 70% of PT and PTT tests were not clinically indicated. The risk of intraoperative bleeding is best predicted from a careful history that includes a questionnaire-based bleeding assessment test (BAT).”

My colleague, Prof. Miller, and I are curious if you have had a similar event and if you’ve discussed it with your physician. Please respond in our comments section.

Comments (0)
Screening Assays

No comments here.

Leave a Reply