PREVALENCE AND CLINICAL-SIGNIFICANCE OF ELEVATED ANTIPHOSPHOLIPID ANTIBODIES IN PATIENTS WITH IDIOPATHIC THROMBOCYTOPENIC PURPURA

Antibodies against phospholipid antigens (APA) have been demonstrated in idiopathic thrombocytopenic purpura (ITP), but their clinical and p athogenetic significance has remained elusive. In this study we analyz ed the prevalence and clinical features of ITP patients with elevated APA. In addition, we prospectively evaluated APA levels after treatmen t with corticosteroids and compared them with platelet-associated immu noglobulin (PAlgG) titers. We studied 149 patients with newly diagnose d ITP. Of these, 78 had a platelet count less than 50 x 10(9)/L and re ceived an initial treatment with oral prednisone (PDN). In 71 asymptom atic cases with platelet counts between 50 x 10(9)/L and 120 x 10(9)/L , no therapy was scheduled. However, in five of them, the platelet cou nt fell below 50 x 10(9)/L after more than 12 months; these patients w ere treated with PDN. Tests for APA included the measurement of antica rdiolipin antibodies (ACA) with a solid-phase immunoassay and the dete ction of the lupus-like anticoagulant (LA) activity with coagulation t ests that included kaolin-clotting time, dilute Russel's Viper venom t ime, activated partial thromboplastin time (aPTT), and dilute aPTT. Co ntrols consisted of 174 apparently healthy subjects. Either LA or elev ated ACA was seen in 69 patients (46.3%) at diagnosis. LA and ACA were both elevated in 24 cases (16.1% of the overall patient population an d 34.8% of patients with high APA concentrations). No correlation was found between LA ratio values and ACA-IgG or -IgM titers, or between A CA-IgG and ACA-IgM levels. The presence of these antibodies was not as sociated with sex, age, platelet count, or the severity of hemorrhages . PAlgG was detected in 106 of 127 cases (83%). Again, no relationship was observed with clinical parameters or with APA levels. However, al l cases with elevated APA also had increased PAlgG. With regard to the clinical course, we were not able to detect any significant differenc e between patients with normal and elevated APA. An initial complete r esponse to prednisone treatment was observed in 43 of 83 cases (51.8%) , with 13 (15.7%) achieving a prolonged complete remission. APA levels were not significantly modified after PDN therapy and on relapse. We conclude that APA positivity is a common finding in patients with ITP and does not select a category with different clinical features. APA l evels are not influenced by immunosuppressive therapy with steroids an d are not related to the activity of the disease. Therefore, we do not support a role for APA in the pathogenesis of ITP. (C) 1994 by The Am erican Society of Hematology.