Bio Plus ESR tube is mainly used for the test of blood coagulation mechanism. It is filled with
buffered sodium citrate solution, and citrate concentrations of either 0.109mol/l (3.2%) or
0.129mol/l (3.8%) are available. The choice of the concentration depends upon the policies
of the laboratories. Care for that soon after blood, mixing it 5-6 times by turning the tube 180°.