From Kelly Townsend, Tri-core Reference Laboratories, Albuquerque. Looking for opinions on what constitutes a “Laboratory Developed Test” in Coag. Obviously if the reagent kit is not FDA-cleared, it will be an LDT, but what about factor assays, etc where there is no real kit. What if you are using a kit with a different calibrator or control than the manufacturer sells/endorses? Having trouble coming up with a concise definition for LDT. Thanks, Kelly.
Category: Factor Assays
From Pam Owens: Hi George, good to see you at THSNA! (Thrombosis and Hemostasis Summit of North America). I am hearing more about how ineffective the 5M urea test is for factor XIII screening and am thinking we just need to stop doing the assay in our lab. I’ll need to convince our lab director. Are there any articles or published studies out there? I’m not having any luck looking on line.
Each year George enjoys the opportunity to teach in Dr. Elaine Keohane’s graduate course, CLSC 5124, Advanced Hemostasis at Rutgers University School of Health Related Professions. Our students are experienced medical laboratory scientists from all over the world, and they bring a wealth of practical knowledge. Dr. Keohane is teaching a section on platelet physiology this week, and the question came up, what is platelet factor 3? I’m old enough to know the answer, but I’d like to hear from our participants. In addition to defining PF3, also please report what coagulation laboratory assay we used to “diagnose” PF3 deficiency.
From Deborah Whetzel, Children’s Hospital of the King’s Daughters, Norfolk, VA: We’ve had a couple patients lately that demonstrated inhibition but their factor VIII results are within normal limits or even elevated. The result values differ 30–40% typically between dilutions but as they’re diluted more, the values go up to 300 or 400%. FVIII values that high seem really odd to me. We dilute to 1:160, as I’ve seen recommended, with results to that point continuing to get higher. Have you seen this occur and is there something that we should be doing? Thanks for your help.
From Kim Kinney, Indiana University Health, Hi George! We have a severe hemophiliac with an 8BU inhibitor receiving ReFacto. Factor assays are high, but dilutions dilute backward! 367, 238, then 183, then 167 causing a CV flag. We have seen this before, but have never heard an explanation for the “backward” dilution affect. Can you shed light? It does not happen on all treated hemophiliacs…is it the ReFacto? Thanks for the info!
From Manju Bala, St Christopher’s Hospital for Children. Need help with interpreting a coagulation dilemma. A child, 4 months old, post cardiac surgery, no meds, use of bovine thrombin during surgery with prolonged prothrombin time (PT), 29.9s; partial thromboplastin time (PTT, APTT),107.7s; and thrombin time (TT), 40.4s; no correction on mixing. FII, 25%; FV, 7%, increasing with dilution; FVIII, 129%; FIX, 39%; FX, 69% and FXI, 50%. The latter four factors, although normal appear to increase on dilution like an inhibitor. No evidence of bleeding, no evidence of thrombosis, liver function tests normal. Could this be due to an antibody to bovine thrombin or lupus anticoagulant? Testing is pending.
From Saravanan Vinayagam: We are trying to set up the factor VIII inhibitor assay on our ACL TOP analysers. Has anyone got an SOP or previous experience in validating inhibitor assay in an automated analysers? Thank you.
Hello, Saravanan Vinayagam, and thank you for your post. I’m hoping that an IL technical representative will see this and offer some assistance. Geo.
Another from Linda Stang, Alberta Health Service: We have a patient with ‘transient, recurrent’ factor VII deficiency that I suspect is drug related. When FVII is low, protein C and factor X are normal. Patient has been as high as 1.57 u/mL and as low as 0.08 u/mL. Do you or any of your participants have any experience with this or any references? Thanks so much, Linda.