This was posted by a colleague on another forum. We have noticed that newborn babies plasma, after three weeks on extracorporeal membrane oxygenation (ECMO) becomes dark brown. On our instrument, the fibrinogen rises to approximately 800 mg/dL, though a reference lab reports it as critically low. We also notice falsely elevated platelet counts, for instance, 150,000 by impedance and 50,000 by optical, but the manual estimate is 15,000. The manufacturer says the fibrinogen could cause a falsely elevated platelet count. Could there be a common denominator causing these interferences?
Category: Specimen Management
George presented the first part of a three-part AACC webinar series, Quality Assurance in Hemostasis; What Makes Us Different? A question arose about Ebola virus specimen management. Though not specifically related to hemostasis, it seems appropriate to provide a link to the US Centers for Disease Control and Prevention (CDC) specimen precautions. What the CDC document does not address is potential instrument contamination. George suggested specimens identified as Ebola should be tested on isolated instruments. How do you manage infections specimens, and what do you recommend?
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 »
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.