Prevalence and Specificity of Anti-HPA and Anti-HLA Antibodies in Patients with Suspected Immune-Mediated Platelet Disorders: A Single-Center Study from Serbia.

Background and

Objectives

Alloantibodies directed against human platelet antigens and human leukocyte antigens are implicated in several immune-mediated platelet disorders, including platelet transfusion refractoriness, post-transfusion purpura and fetal and neonatal alloimmune thrombocytopenia. Reliable and simultaneous detection of these antibodies is essential for accurate diagnosis and appropriate clinical management. The aim of this study was to determine the prevalence and specificity spectrum of anti-HLA and anti-HPA alloantibodies in patients with suspected immune-mediated platelet disorders using a multiplex bead-based assay, and to evaluate its diagnostic utility in a Serbian cohort. Materials and

Methods

A bead-based glycoprotein-specific antibody detection assay was performed using monoclonal antibodies specific for platelet glycoproteins and HLA class I molecules, separately coupled to Luminex microbeads. Serum samples were collected from 259 patients, including 234 patients with thrombocytopenia, 11 with neonatal alloimmune thrombocytopenia, and 14 with suspected platelet transfusion refractoriness. All samples were tested using the PakLx Luminex assay, and results were interpreted with MatchIt! Antibody software.

Results

Of the 259 tested samples, 72 (27.8%) were positive for HLA and/or platelet-specific antibodies. Among the positive samples, 29.2% contained HLA class I antibodies, 45.8% contained platelet-specific antibodies, and 25% showed combined HLA and platelet antibody positivity. The most frequently detected platelet-specific antibodies were directed against GPIIb/IIIa (HPA-1, -3, -4) and GPIa/IIa (HPA-5).

Conclusions

This first analysis of platelet alloantibodies in a Serbian cohort demonstrates a high prevalence of antibody positivity in patients with neonatal alloimmune thrombocytopenia and platelet transfusion refractoriness, with anti-HPA-1a as the predominant specificity. The significant association between clinical presentation and antibody profile underscores the need for targeted diagnostic testing. Multiplex bead-based technology provides comprehensive alloantibody detection, facilitating optimized transfusion management in immune-mediated platelet disorders.