American Society for Clinical Laboratory Science

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September 13, 2021

Avoid routine prothrombin time (PT) and partial thromboplastin time (PTT, APTT) pre-operative screens on asymptomatic patients, use instead a history-based bleeding assessment test.

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. Subsequently, nine observational studies, including three prospective trials, reported that PT and PTT positive predictive values for bleeding complications ranged from 0.03 to 0.22, whereas computed 95% confidence intervals for each assay generates a 2.5% false positive rate. 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 risk of intraoperative bleeding is best predicted from a careful history that includes a questionnaire-based bleeding assessment test (BAT).

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How The List Was Created

George Fritsma, MS, MLS (ASCP), and the late Cindy Johns, MS, MLS (ASCP) hosted a plenary presentation “Enhancing Laboratory Communication to Reduce Extra-analytical Errors” at the ASCLS Clinical Laboratory Educators’ Conference in Boston in February 2017. Their talk referenced the ABIMF Choosing Wisely initiative. Subsequent discussions resulted in the ASCLS Board of Directors appointing a Choosing Wisely task force that evolved to a standing committee. The committee is composed of ASCLS members representing all medical laboratory science disciplines.

The committee collaborated with respective ASCLS Scientific Assemblies in developing and reviewing recommendations, which the Board of Directors reviewed and accepted for publication. The recommendations were subsequently reviewed in collaboration with the ASCP Test Utilization Steering Committee prior to submission.



American Society for Clinical Laboratory Science (ASCLS) recommendations were developed under the leadership of ASCLS’s Choosing Wisely Committee and the ASCLS president and executive vice president. The Committee examined numerous options based on evidence available through an extensive review of  the literature and member proposals. Subject matter experts from the ASCLS Scientific Assemblies reviewed and recommended approval of their respective recommendations, which are subsequently approved by the ASCLS Board of Directors. The recommendations were subsequently reviewed in collaboration with the ASCP Test Utilization Steering Committee prior to submission.


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