Potential Clinical Impact of Inaccurate Automated Platelet Counts in the Setting of Severe Thrombocytopenia

Abstract 3428 Severe thrombocytopenia is not an uncommon finding in the setting of hematologic malignancies. The key to a successful outcome often lies in the ability to support the patient through periods of cytopenia by adopting an aggressive transfusion strategy for platelets. Therefore, an accurate assessment of the platelet count is of utmost importance particularly as it relates to various levels which “trigger” prophylactic platelet transfusion. However, the accuracy and precision of conventional platelet counting methods have been shown to be suspect in severely thrombocytopenic samples. We investigated the accuracy of several commercial hematology analyzers currently available in clinical practice which use optical, impedance and immunologic platelet determination methods and assessed whether biased results could have an impact on decisions regarding platelet transfusion. Four-hundred three (403) EDTA-anticoagulated samples collected from patients with hematologic malignancies and a platelet count of r =0.99, y = −0.96 + 0.88x; n = 37). Also, the International Counsel for Standardization in Haematology and the International Society for Laboratory Hematology recommend the counting of specifically labelled platelets (CD41, CD61) by flow cytometry as a reference method for the enumeration of platelets. Bland-Altman difference plots were used to visualize the agreement between the reference and test methods and the paired t-test evaluated the statistical significance of the difference between methods. We then compared the number of platelet transfusion indications (at various platelet thresholds) as determined by all methods with potential transfusion decisions made using the reference method. There was a statistically significant positive bias among the optical and impedance methods compared with CD61 enumeration. Using various platelet transfusion decision points, the number of patients who were at risk for under transfusion (platelet count above threshold when reference result is Disclosures: Marionneaux: Abbott Diagnostics: Consultancy.