Anti-Glycoprotein Antibodies and Sequestration Pattern of Indium Labeled Platelets in Immune Thrombocytopenia.

Anti-glycoprotein antibodies play an important role in the pathophysiology of immune thrombocytopenia (ITP). The sequestration pattern of platelets in spleen and liver can be studied with Indium-111 labeled autologous platelet scans. No studies have investigated the role of anti-GP antibodies in sequestration pattern in ITP patients. In this study we examined the association between antibodies and 1) platelet sequestration site and 2) clearance rate of platelets. All ITP patients receiving an Indium-111 labeled autologous platelet study between 2014 and 2018 were included. Antibodies were measured using the direct MAIPA method to determine the presence and titer of anti-GPIIb/IIIa, anti-GPIb/IX and anti-GPV antibodies. Multivariate regression models were used to study the association between anti-GP antibodies, sequestration site and clearance rate. Seventy-four patients were included, with a mean age of 36 years. Forty-seven percent of the patients showed a predominantly splenic sequestration pattern, 29% mixed and 25% a hepatic pattern. In 53% of the patients anti-GP antibodies were detected. Regression models showed a significant association between splenic sequestration and GPV autoantibodies.. Furthermore, in patients where antibodies were present the clearance rate was higher in patients with a splenic sequestration. Anti-GPV antibodies are associated with a splenic sequestration pattern in ITP patients. These associations provide insight in the possible pathophysiological mechanisms of ITP, which may lead to better detection and treatment of this partly idiopathic and prevalent disease.