Jul 30 2014
George is attending the annual AACC meeting at McCormick Place in Chicago. A colleague described a puzzling case in which a patient has a prolonged prothrombin time (PT) using a 1.3 ISI thromboplastin reagent (Stago) and a normal PT when using Dade (Siemens) Innovin. The findings are consistent on repeat split specimens, the PTT is normal, and the patient is not bleeding. Any ideas?
Comments (3)
Screening Assays
Person might develop antibody against rabbit, which could in
Person might develop antibody against rabbit, which could interact with thromboplastin.
Entirely feasible. Also see: Girolami A, Scandellari R, Lomb
Entirely feasible. Also see: Girolami A, Scandellari R, Lombardi AM. The use of tissue thromboplastins of different origin is a fundamental tool in the initial characterization of FVII defects of “factor VII deficiency.” Semin Thromb Hemost 2009;35:4006). Also Semin Thromb Hemost 2010;36:1234; with author reply 125-7.
If these two particular reagents were used: Neoplastin Plus,
If these two particular reagents were used: Neoplastin Plus, rabbit brain, Stago, coagulometer-specific ISI 1.31, and Innovin, recombinant human tissue factor, Siemens, this discrepancy (abnormal PT with rabbit thromboplastin, and normal PT with synthetic human thromboplastin) could come from inherited factor VII Padua (Arg304Gln) mutation: “FVII level is low when rabbit brain thromboplastin is used, whereas the level is perfectly normal when ox-brain thromboplastin is employed. Intermediate levels are obtained if human placenta or human recombinant is used.”
Girolami A, et al. Diagnosis of FVII Padua (Arg304Gln) by means of simple clotting tests. Clin Chim Acta. 2010 Dec 14;411(23-24):2107-8.
Girolami A, et al. Worldwide diffusion of FVII Arg304Gln coagulation defect (FVII Padua). Eur J Haematol. 2011 Feb;86(2):135-9. http://www.ncbi.nlm.nih.gov/pubmed/20958793
Pollak ES et al. Asymptomatic Factor VII Deficiency in African Americans.
http://ajcp.ascpjournals.org/content/126/1/128.long