Accuracy evaluation of low platelet counts on the cobas m 511 integrated hematology analyzer

Introduction: The cobas m 511 integrated hematology analyzer is a novel slide-based system that performs a complete blood count, WBC differential, reticulocyte count, and nucleated RBC count using digital analysis of a microscope slide. This single-center study at Erasmus MC assessed the accuracy of low platelet (PLT) counts on the cobas m 511 compared with the Sysmex® XN-10 Automated Hematology Analyzer and BD FACSCanto™ Flow Cytometry System. Methods: Residual whole blood samples (n=115) in the PLT range 1-505 x 103/μL (based on flow cytometer results) were randomly processed on the three systems. Sysmex samples were set to automatically reflex to PLT-F function, which is marketed as more reliable for thrombocytic or problematic samples than the standard impedance PLT-I function. Three analyses were performed: cobas m 511 and Sysmex Analyzer versus flow cytometer (reference), and cobas m 511 versus Sysmex Analyzer (reference). For each analysis, three different thresholds were used and results were included if a valid PLT result was obtained on both systems. Results: The cobas m 511 demonstrated excellent accuracy compared with flow cytometry, with ≥90% sensitivity, specificity, and agreement, and good accuracy compared with Sysmex Analyzer (Table 1). Attempts were made to also study flags for the Sysmex Analyzer PLT-I function; however, excessive flagging (100% for PLT counts ≤10, 80% for PLT 11-20, and 28% for PLT 21-50 x 103/μL) indicated these values were unreliable and prevented any further comparison. (Table presented) Conclusions: These data demonstrate the robustness and accuracy of platelet counts reported by the cobas m 511 system. Many samples were flagged using the Sysmex PLT-I function that, in routine use, would have reflexed to the PLT-F function. All samples on the cobas m 511 system had valid PLT results. COBAS and COBAS M are trademarks of Roche. Other product names and trademarks are the property of their respective owners.