Measurement of platelet clearance kinetics. (A) Endogenous platelet count is monitored over time following the injection of a reagent to assess its effect on platelet clearance. (B) A radioisotopic or fluorescent compound is administered into human or mice. Thereafter, the percentage or radioactivity of labeled platelets in the whole platelet population is measured over time. (C) Exogenous platelets are labeled with radioisotopes or chromophores, and transfused into a host. The percentage of these exogenous labeled platelets is measured over time. The recovery indicates the initial appearance of transfused platelet in the circulation, and the survival means the time that the transfused platelets stay in the circulation.