Therapeutic Ranges for LMWH and Fondaparinux

From Pamela Owens at Tricore in Albuquerque:

1. What therapeutic ranges are folks using for the pentasaccharide fondaparinux (Arixtra)? How were the ranges determined? The ranges in the Arixtra package insert are extremely narrow.

2. Concerning the monitoring of low molecular weight heparin (LMWH): Are labs publishing separate therapeutic ranges for once-a-day dosing versus twice-a-day dosing? How were those ranges determined? What ranges are labs using for once a day dosing? There seems to be more info in the literature concerning twice a day dosing.


Read more »

Factor Substitution Assays

From: Peracha,

Mr. Fritsma: We do not have facilities for factor assays at our laboratory. I need to prepare aged plasma for correction studies. Should aged plasma have a prothrombin time exceeding 90 seconds or should it be not more than 90 seconds?

Read more »

A Thrombocytopenia Saga

George attempted to answer this question about thrombocytopenia, which appeared on the ASCLS Consumer Forum, in November of 2008
I am a medical technologist. My platelet count has been running around 102,000/uL for the past few years. This year Quest Diagnostics did my blood work and the count was 87,000. I thought it may have something to do with the EDTA, so I had it rerun with both EDTA and citrated plasma and the counts were 95,000 and 98,000. I even diluted the EDTA specimen with saline 1/1 and reran, with the result the same. Everything looked normal on the blood film. We estimated the platelets in ten fields and came up with an average of 9 platelets/field. The formula we use is to multiply the average by 20,000, and the resulting estimate from that was 180,000. My WBC, RBC, HGB, HCT, MCV, MCH, RDW, etc. are all normal. I have no obvious symptoms of bleeding or bruising. Any clues as to my low count?
Read more »

New Unfractionated Heparin Formulation (Yet Again)

Joe Lamb, Hematology/Blood Bank Supervisor at St. Francis Hospital Laboratory, Columbus, GA sent me this valuable heads-up:
George, you probably know this already (I didn’t) but the December CAP Today has a question and answer tidbit by Dr. Charles Eby about the new heparin formulation and validation studies. Thanks to Joe, you can follow the link to Dr. Eby’s summary.

Lupus Anticoagulant Testing and Pooled Normal Plasma

A question about pooled normal plasma for lupus anticoagulant testing from Theo Powers, US Oncology.

Hello, George! Great web site,

The updated guidelines for lupus anticoagulant (LA) testing refer to making in-house pooled normal plasma (PNP). What are the current recommendations for preparing this pool, such as number of donors, storage, stability? Triplett (Laboratory Evaluation of Coagulation, 1982) recommended six normal donors. I’ve seen recommendations for 10, 20, 40 normal donors. I look forward to hearing your reply, as my resources are older. Theo Powers MT (ASCP)

Read more »

New Quick Question: INR

Please take a moment to answer the quick question posted today, Tuesday, December 15. If you have a question you’d like to see posted as a quick question, please send it to George using the “Ask George” link.

Quick Question Summary: Specimen Hemolysis

Our November Quick Question was “What is your institution’s policy regarding artifactual hemolysis?

a. Ignore hemolysis: 4% (3)
b. Reject all plasmas with visible hemolysis: 49% (34)
c. Assay anyway and append a comment indicating possible interference: 36% (25)
d. Assay for plasma hemoglobin and reject plasmas above an established limit: 11% (8)

Read more »

Coagulation Cofactors: Why They Aren’t Catalysts

A basic coagulation question from my colleague and co-editor Kathryn Doig, PhD, Michigan State University Clinical Laboratory Science Program:

Hi, George. A student and I got into a discussion about the role of factors V and VIII.  He contends they are catalysts because they increase the rate of the reactions in which they are involved and are not changed by the reaction.  I contend that they are not catalysts because they are not then freed to react again.

On page 576 of Rodak BF, Fritsma FA, Doig K. Hematology; Clinical Principles and Applications, 3rd Edition you indicate that cofactors give their enzymes stability that increases reactivity. Would you agree that they are not truly catalysts mainly because they are not freed to react again?

Read more »

WordPress Themes