Inpatient Thrombophilia Testing

Another message from colleague and friend Kelly Townsend, Tricore Reference Laboratories, Albuquerque. Hi George, at one of our large teaching hospitals, we are working with the Internal Medicine department to establish “best practices” for ordering thrombophilia testing on inpatients. Has anyone out there successfully implemented guidelines they are willing to share? Any recent references would also be greatly appreciated. Thanks!
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Revalidating Sta-Clot LA

From Rose Markarian, Supervisor Hematology,  Saint John’s Health Center, Santa Monica, CA: Hi George, We perform Stago’s confirmatory hexagonal phase Sta-Clot LA test for lupus inhibitor testing. We validated Stago’s recommended cut off value of ≤ 8.0 seconds several years ago when the test was implemented. Do we have to validate the cut off value with each new lot of reagent? Please advise.
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Platelet Clumping

From Kelly Townsend at Tricore Labs: We have a patient whose platelets clump in every anticoagulant we’ve tried. He has normal prothrombin time, partial thromboplastin time, fibrinogen, and von Willebrand disease panel results, but oozes after even minor procedures. The clinicians want to evaluate platelet function, but we are hesitant because of his platelet clumping. Any suggestions for obtaining accurate platelet function analyzer (PFA-100)  and/or platelet aggregation results in a platelet clumper? We use the Chrono-log Lumiaggregometer (whole blood).

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How Long to Stop Infusion

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?

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Discard Tubes for Heparin?

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?

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Anti-Xa versus PTT

Hi George! Our HCO is wanting to change unfractionated heparin (UFH) monitoring to the anti-Xa test from the partial thromboplastin time (PTT). The research supports decreased lenghth of stay, quicker theurapeutic range achievement and improved patient safety monitoring with anti-Xa, as many patients may appear theurapeutic with the PTT but may actually be under or over anticoagulated. Our physicians seem to know nothing about anti-Xa as well as few of our lab co-workers and do not see the need to change. What are your thoughts? Julia Witt.

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Quick Question: PTT Mixing Studies

The results of our January-February 2014 Quick Question:

Does your laboratory perform follow-up partial thromboplastin time (PTT) mixing studies 24/7?

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CPT Code for SCT?

From Molly Klima, University Hospitals of Cleveland: Hi George, we are in the process of bringing up the Instrumentation Laboratory Silica Clotting Time (SCT) assay and are struggling with the CPT code. Since there is no straightforward CPT for the assay our dilemma is as follows:

  • 85730 Thromboplastin time, partial (PTT); plasma or whole blood
  • 85732 Thromboplastin time, partial (PTT); plasma or whole blood substitution, plasma fractions, each

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