George is working with Dr. Jeanine Walenga, coagulation editor, on the “Methods” chapter for the fifth edition of Hematology, Clinical Principles and Applications. (The Rodak Hematology textbook published by Elsevier). While most hemostasis specimens are collected in evacuated tube systems, we use syringes for difficult draws or special applications. When transferring syringe blood to an evacuated tube, the general rule, outlined in CLSI H3-A6, is to detach the needle, affix a safety transfer device, pierce the tube closure, and allow the negative pressure of the tube to draw the proper volume of blood from the syringe, ensuring it runs gently down the side of the tube. Read more »
Category: Specimen Management
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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From Kim Kinney at Indiana University Health:
Hi George. We frequently get asked how long to stop an unfractionated heparin infusion before drawing for a partial thromboplastin time (PTT) from a central line or peripheral stick above the infusion site. We have always referred them to pharmacy. is there a standard practice used by nursing at other institutions that someone would share?
From Dennis Ernst, Center for Phlebotomy Education, Inc: I am chairing the CLSI Document Development Committee on the venipuncture standard revision. At today’s web meeting the question came up about the necessity for discard tubes on heparinized patients. It’s been widely reported that discard tubes are not necessary, and haven’t been for some time. However, it came to our attention today that the passage in the CLSI coag standard (H21) that states discard tubes are not necessary for partial thromboplastin time assays (PTTs, APTTs) and prothrombin times (PTs), for that matter cites four studies, all of which have been conducted on patients who are not on heparin therapy. Here are the citations:
- Gottfried EL, Adachi MM. Prothrombin time and activated partial thromboplastin time can be performed on the first tube. Am J Clin Pathol. 1997;107:681–3.
- Adcock DM, Kressin DC, Marlar RA. Are discard tubes necessary in coagulation studies? Lab Med. 1997;28:530–3.
- Yawn B, Loge C, Dale J. Prothrombin time, one tube or two. Am J Clin Pathol. 1996;105:794–7.
- Bamberg R, Cottle J, Williams J. Effect of drawing a discard tube on PT and APTT results in healthy adults. Clin Lab Sci. 2003;16:16-19.
Are you aware of any study that had attempted to establish discard tubes may not be necessary for heparinized patients as well? In your opinion, is it safe to assume it shouldn’t matter if they are heparinized or not?
From Gnaesh Lyer, Florida Hospital: Have you done any correlation studies for Plavix and aspirin if the tubes are sent by tube system from floors rather than hand delivering the tubes? Does the results vary a lot or with in acceptable range? Thanks.
Hello, Gnaesh Lyer, and thank you for your question. I know of no studies that examine the effect of specimen tube system agitation affecting platelet function assay results, and have forwarded your question to several colleagues to learn if anyone has unpublished data on the subject. Perhaps one of our participants may have a comment to add.
Irene Regan writes that despite doing major literature searches there seems to be no consensus regarding what coagulation results should be released when there is a suspicion of in vivo hemolysis such as in disseminated intravascular coagulation (DIC), when the samples are grossly haemolysed. Currently, Irene issues a fibrinogen (Clauss) and in this case she generally confirms this using a correction with normal plasma due to haemolysed nature of the sample or because the fibrinogen is extremely low. Do you have any advise?
From our frequent contributor, Kim Kinney at Indiana University Health Pathology Laboratory: Merry Christmas all! George, this may be an old topic, but I am getting some push back from our off-site coordinators. Coagulation samples sent on ice: I have always thought that the current literature stated that iced coag tubes could activate factor VII and potentially shorten the prothrombin time (PT). Is there current literature out there surrounding this topic? Any information would be helpful!
From Anita Elledge, MT (ASCP), blood bank/coagulation supervisor, Sierra Vista Regional Health Center, AZ: Our coagulation testing is done on a Stago Compact instrument. The linear range is 20–200 s for the activated partial thromboplastin time (APTT, PTT). We have a policy that any PTT result <22 s must be redrawn, not just rerun the same sample, because it is said that a low PTT result should not occur and is almost always due to a bad collection. I can’t seem to find any documentation that confirms the < 22 s result being a point for this “recollect.” Can you give me a resource for information or any further help with this?