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 coun ters, which may affect samples from thrombocytopenic patients (less than 10 0,000/mu L). Therefore, we mixed clinically relevant concentrations of perf luorodichlorooctane (Oxyfluor(R); Hemagen, Inc., St. Louis, MO) in vitro wi th whole blood samples ranging from 0 to 150,000 platelets/mu L and compare d a new counter that uses optical platelet recognition (Abbott CellDyn 3200 ; Santa Clara, CA) with conventional electroimpedance-based counters (Abbot t CellDyn 3500 and CellDyn 1700). We found that emulsion particles appear a s small-sized platelets either in diluent or in blood. The emulsion results in a reproducible overestimate of the platelet counts, of greater importan ce as PFE concentration increases, and as the actual platelet count of the blood samples decreases. The new optical technology yields smaller overesti mates but, even at low PFE concentrations, gives an unacceptable relative e rror at platelet counts near the transfusion thresholds recommended by the American Society of Anesthesiologists guidelines for blood component therap y. Unexpected interference in the leukocyte and erythrocyte channels is als o reported. Experimental limitations preclude extrapolation of these findin gs to other automated cell counters, because differences in technology or s oftware 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 demon strate significant overestimates in platelet counts from automated cell cou nters at clinically relevant perfluorocarbon concentrations in thrombocytop enic blood samples.