A NEW CASE OF ACQUIRED GLANZMANN'S THROMBASTHENIA: COMPARATIVE EVALUATION OF THE DIAGNOSTIC VALUE OF DIFFERENT PLATELET FUNCTION TESTS
Abstract number: P-S-313
Giannini1 S., Rossi1 R., Mezzasoma1 A., Guglielmini1 G., Falcinelli1 E., Gresele1 P.
1Internal Medicine, Div. Internal and Cardiovascular Medicine, Univ. Perugia, Perugia, Italy
How-to-cite Giannini S, Rossi R, Mezzasoma A, Guglielmini G, Falcinelli E, Gresele P. A NEW CASE OF ACQUIRED GLANZMANN'S THROMBASTHENIA: COMPARATIVE EVALUATION OF THE DIAGNOSTIC VALUE OF DIFFERENT PLATELET FUNCTION TESTS. J Thromb Haemost 2007; 5 Supplement 2: P-S-313
Abstract
Introduction: Acquired Glanzmann's thrombasthenia (aGT) is a rare hemorrhagic disorder caused by an autoantibody against platelet GPIIb/IIIa.The diagnosis requires several laboratory assays among which mixing tests, complex and time consuming.
We characterized a new case of aGT and compared different platelet function tests for the detection of GPIIb/IIIa blocking autoantibodies.
Methods: A previously healthy 27 years old male developed severe mucocutaneous bleeding despite a normal platelet count. A B-cell, non Hodgkin lymphoma was diagnosed. Platelet function was evaluated, repeatedly over two years follow-up, by several tests.
Results: Platelet count, aPTT, PT, fibrinogen, vWf:Ag, vWf:Rco and XDP were normal. Skin bleeding time and PFA-100® were unmeasurable.
Platelet aggregation was absent in response to all agonists except ristocetin. Platelet adhesion on a collagenated surface at high shear was markedly reduced. Normal platelet granular content and release was shown by flow cytometry (P-selectin and mepacrine). Flow cytometry showed a normal expression of platelet GPIIb/IIIa with some anti-GPIIb/IIIa clones (SZ21 and SAP), but decreased with others: P2 (-23.4%), SZ22 (-43.1%) and A2A6/9 (-87.6%). Platelet binding of PAC-1, against activated GPIIb/IIIa, and of fibrinogen, induced by TRAP-6 or ADP, was absent. Addition of patient's serum to control platelets inhibited PAC-1 and SZ22 binding by flow cytometry, aggregation and adhesion at high shear. Flow cytometry was the only test able to characterize the specific defect induced by patient's serum on GPIIb/IIIa. Patient's antibody, purified by GPIIb/IIIa affinity chromatography, was an IgG3.
Conclusions: We applied several techniques to the diagnosis of a new case of aGT and shown that flow cytometry is especially useful for the rapidity of the assay, for the small volume of sample required and for its sensitivity and specificity in the study of the expression and activation of platelet GPIIb/IIIa and of its inhibition by GPIIb/IIIa blocking antibodies.
