A second-generation blood substitute (perfluorodichlorooctane emulsion) generates spurious elevations in platelet counts from automated hematology analyzers

Perfluorocarbon emulsions (PFEs) appear as platelets in automated cell counters, which may affect samples from thrombocytopenic patients (less than 100,000/μL). Therefore, we mixed clinically relevant concentrations of perfluorodichlorooctane (Oxyfluor®; Hemagen, Inc., St. Louis, MO) in vitro with whole blood samples ranging from 0 to 150,000 platelets/μL and compared a new counter that uses optical platelet recognition (Abbott CellDyn 3200; Santa Clara, CA) with conventional electroimpedance-based counters (Abbott CellDyn 3500 and CellDyn 1700). We found that emulsion particles appear as small-sized platelets either in diluent or in blood. The emulsion results in a reproducible overestimate of the platelet counts, of greater importance as PFE concentration increases, and as the actual platelet count of the blood samples decreases. The new optical technology yields smaller overestimates but, even at low PFE concentrations, gives an unacceptable relative error at platelet counts near the transfusion thresholds recommended by the American Society of Anesthesiologists guidelines for blood component therapy. Unexpected interference in the leukocyte and erythrocyte channels is also reported. Experimental limitations preclude extrapolation of these findings to other automated cell counters, because differences in technology or software may affect their capacity to separate PFE particles from platelets. Implications: Perfluorocarbons are being investigated under conditions in which thrombocytopenia is likely to occur. In this in vitro study, we demonstrate significant overestimates in platelet counts from automated cell counters at clinically relevant perfluorocarbon concentrations in thrombocytopenic blood samples.