Cassandra McGeachy, Louisiana Coagulation, asks, I am trying to evaluate a set of FVIII inhibitor results and I am not sure what to call it. My patient + normal pool on my Bethesda assay yields a 23% FVIII and the next 4 serial dilutions bounce around between 15 to 19% instead of giving a higher value. Since this is a possible acquired FVIII inhibitor case I asked the tech to repeat the test using the Nijmegan method. This test method basically yields the same thing with the patient + pool giving 15% FVIII and the next 5 serial dilutions yielding results of 15 to 19% but no higher. What causes this and how to you report the result? Do you know of any references for this pattern demonstrated when performing the inhibitor titer?
Hello, Cassy, and thanks for your question. I’m not sure I have an answer for you, but I want to get this posted to learn if anyone has had a similar situation. I’m assuming you’ve run a lupus anticoagulant profile on the plasma and ruled out an LA as an interference? Also a thrombin time for heparin? I found a recent case study that seems to parallel your situation, Abt NB, Streiff MB, Gocke CB, Kickler TS, Lanzkron SM. Idiopathic acquired hemophilia A with undetectable factor VIII inhibitor. Case Rep Hematol. 2014;2014:484563. doi: 10.1155/2014/484563. Epub 2014 May 14. The article is a free download, but I’m not sure it actually provides an answer.