From Elaine Benoit, Precision BioLogic. Hi, George. Thursday, April 17 was World Hemophilia Day. Precision is a sponsor of the World Federation of Hemophilia and as part of their World Hemophilia Day activities, we had the opportunity to create and submit an infographic that they posted on their Facebook page. There are several infographics there; ours depicts hemophilia from a child’s perspective – how a young boy might describe his experiences to a friend. Take a look!
From frequent contributor, Kim Kinney: Hi George, our Indiana University Health Pathology Laboratory is thinking of making the push again to use the Anti-Xa to monitor unfractionated (UFH) heparin therapy in place of the activated partial thromboplastin time (aPTT). I would like to hear from institutions that have made the transition successfully even in light of the fact that the chromogenic anti-Xa is a more expensive test than the aPTT. That seems to be where our admin gets stuck.
Hello, Kim and thank you for bringing up this important topic, which is addressed most recently in Wool GD, Lu CM; Education Committee of the Academy of Clinical Laboratory Physicians and Scientists. Pathology consultation on anticoagulation monitoring: factor X-related assays. Am J Clin Pathol. 2013; 140: 623–34. I’m eager to hear from our participants, but just to throw in my own opinion, when you compare and graph the anti-Xa to the PTT using routine daily specimens, and not just your carefully selected set of therapeutic target range aliquots, you strikingly illustrate the PTT’s unreliability. In addition, the anti-Xa can be used to measure not only unfractionated standard heparin, but also low molecular weight heparin and the pentasaccharide fondaparinux. Further, it is likely to be cleared by the FDA soon to measure the direct oral anti-Xa anticoagulants (DOACs) rivaroxaban, apixaban, and edoxaban. Last week at the Thrombosis and Hemostasis Summit of North America, Dr. Dorothy Adcock indicated it may be possible to assay all the new DOACs using a single, LMWH calibrator set, which would make it even more practical. There already exist “hybrid” calibrators that enable you to use a single curve for both UFH and LMWH, perhaps that curve could even be extended to the DOACs. You may also choose to talk to your ICU nurses, who are faced with the task of adjusting heparin drip rates based on the PTT results. Their efforts are likely to be reduced when using a more precise assay. I hope this helps, and I look forward to our participants’ responses.
George presents “Trauma-Induced Coagulopathy” at the spring meeting, A Patchwork of Knowledge, of the American Society of Clinical Laboratory Science–Missouri (ASCLS-MO) and Kansas (ASCLS-KS) on April 16, 2014 at 9:45 AM. The presentation handout, updated April 15, 2014, is posted here: Hemostasis in Trauma 4-16-14
I pose this question to see what others are doing in this scenario and what literature there is to support your practice. We commonly get mixing study requests in which the PT or PTT are just minimally out of our normal range, such as 0.1 seconds outside for PT. Is this 0.1 second enough to do the mixing study or is there a buffer such as one second for PT and slightly more for PTTs in which although it is outside the normal range, that a mixing study could be not done? I don’t recall ever seeing one of these minimally prolonged PT/PTT turn out to be an inhibitor on followup. I would appreciate your feedback. Thanks. Bruce King, M.D.
This question was forwarded by an American Society for Clinical Laboratory Science Consumer Web Forum volunteer: Our hospital currently uses activated clotting time (ACT) results during heart catheterizations to monitor heparin dosage. The ACT is also used as a guide for pulling the sheath. The nurse confirms that the ACT is less than a certain value before removing the sheath. Would it be possible/advisable to use the partial thromboplastin time (PTT) result instead of ACT as a guide to pulling the sheath if the patient has been transferred to a room and the ACT device is not available for testing?
Please join our sponsor Precision BioLogic Inc at Booth 106 in the Thrombosis and Hemostasis Summit of North America Biennial meeting this week, Thursday, April 10–Saturday, April 12, 2014 at the Chicago Sheraton. While there, please plan to visit our posters, McGlasson DL, Fritsma GA, #53: Do We Need To Normalize the Dilute Russell Viper Venom Time Screen/Confirm Ratio?, Thursday, April 10, 4–5:30; and McGlasson DL, Fritsma GA, Ezzell E, Anderson N: #139: Comparison of Four Dabigatran Assays in an Anticoagulation Clinic Population, Friday, April 11, 5–6:30. We look forward to seeing you there.
From “BJ:” I recently cared for a 60 yr old type 2 diabetic in hyperglycemic hyperosmolar state. Initial serum glucose 960. The partial thromboplastin time (PTT) was initially 78 seconds without clear reason. The international normalized ratio (INR) was 1.4. The prothrombin time (PT) was not initially checked. I felt that the value was likely spurious and I repeated the test a few hours later, with normal result. At that time blood glucose had improved to within the 300s with fluids and insulin. Are you aware of a mechanism whereby severe hyperglycemia can cause the PT/PTT to result artifactually high?
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From Joanna Carroll: I was recently told that samples should be double spun prior to long term freezing. Except in the case of heparin testing, I cannot find any evidence to support this. Also can you tell me if there are recommendations on how to handle samples for fibrinogen, D-dimer and unfractionated heparin anti-Xa assays? Our fibrinogen package insert only mentions how long the sample is good for at room temperature, and our D-dimer insert only mentions how to handle the sample after freezing. The CLSI document does not cover these tests. Thanks for your help.
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