A new method for the direct determination of heparin levels in blood

A new, direct and simple method for the determination of heparin levels in blood, based on the complex formation of heparin with protamin, was developed. With excess protamine, heparin forms nano-scaled particles whose sizes range from approx. 100 nm to 200 nm and which can be detected by light-scattering technique. The light-scattering intensity is proportional to the concentration of the particles and, thus, to the concentration of the heparin present. This heparin analysis can be used for fractionated, low-molecular heparins as well as for unfractionated heparins, needing only a small (<1 mL) volume of blood or plasma, respectively. Due to its linearity and sensitivity, the analysis can be applied from low (<10 I.U./kg BM) to high doses (>500 I.E./kg BM) of heparin. Because of the specific reaction of the test to heparin molecules, the disadvantages of several established test methods for blood coagulation (ACT, Hepcon, Heptest etc.) could be eliminated.