Heparin is a highly sulphated glucosaminoglycan characterised by a wide molecular weight range and powerful anticoagulant properties. Heparin is widely used for the treatment and prevention of thrombotic diseases. Heparin is derived from porcine and bovine tissue and is prepared either as unfractionated (UF) heparin or as depolymerised low molecular weight (LMW) heparin. Up to five percent of patients receiving heparin therapy will develop Heparin Induced Thrombocytopenia (Type II) (HIT) as a major complication. This can cause acute arterial thrombosis (‘white clot syndrome’). The onset of the disease is normally 5-15 days after beginning the therapy. If however, the patient was exposed previously, the onset can occur much sooner. A drop in the platelet count of more than 30% compared with the initial platelet concentration (<100 x 109 per litre) is observed. The DiaMed-ID Heparin/PF4 antibody test is a Particle Gel Immuno Assay (PaGIA). Red coloured polymer particles are sensitised with Heparin/PF4 complex (HPF4). When the particles are mixed with patient serum, specific antibodies (of IgG/IgM/IgA nature) react with the HPF4 on the bead surface, causing agglutination of the particles. The reaction mixture is centrifuged through a gel matrix in a microtube to obtain a spatial separation of the agglutinated and non-agglutinated particles. Agglutinated particles are then trapped on top of the gel or distributed within the gel, while free non-agglutinated particles form a button at the bottom of the microtube.