Hello Mr. Fritsma! My name is Agustin Rodriguez
and I am a haematologist from Spain. I have a question for you, if you are so kind to ansxwer it: I have a patient with a lupus anticoagulant. His PTT
(aPTT) is 46 s; normal aPTT is 30 s in my laboratory. The inmediate mixing study 1:1 with normal plasma is 52 s. Can aPTT be more prolonged after mixing with normal plasma than the basal patient aPTT? In most patients with LA
, the aPTT fails to correct with normal plasma but there is no prolongationover
the initial aPTT. Which is the explanation for this question?
Best regards from Spain, Agustin Rodriguez, MD Haematologist, Toledo Hospital (Virgen de la Salud), Spain.
Hello, Dr. Rodriguez, and thank you for your question. Your laboratory is experiencing a phenomenon called “lupus anticoagulant effect.” This seems to occur when using an ellagic acid-based PTT
reagent, and does not occur when using PTT
reagents that employ particulate activators such as silica. I have been unable to find any documentation of “lupus anticoagulant effect” in scientific literature, reports of the effect seem to be purely anecdotal. The theory, unproven, is that the normal plasma provides a cofactor, perhaps β-2-glycoprotein 1, that potentiates the lupus anticoagulant in the mixture.
I must thank my San Antonio, Texas friend and colleague, Dave McGlasson, for assisting with this entry. In the absence of published data, I needed confirmation from a technical expert. I invite our participants to contribute their experience.