18 Trust but Verify: Repeat CBC Sample Measurements Help Identify Automated Hematology Analyzer Errors

Abstract Introduction The precision and accuracy of modern automated hematology analyzers suggest that with proper instrument calibration, clinically significant errors in the measurement of hemoglobin (Hgb) concentration and white blood cell (WBC) count should virtually never occur. Following the identification of a CBC sample for which the Hgb result differed by more than 4 g/dL on successive analyses, we evaluated the reproducibility of Hgb and WBC results obtained using automated hematology analyzers at our institution. Methods We compared duplicate measurements on approximately 27,000 CBC samples that had been automatically analyzed twice by a Sysmex XN-9000 system equipped with four XN-10 analyzer modules (Sysmex, Kobe, Japan). The initial measurement on these samples produced a flagged impedance platelet count result. For such samples, which comprised approximately 10% of all CBCs analyzed during the study period, a second set of CBC results is automatically obtained within two minutes by the same XN-10 analyzer, this time using a fluorescent platelet counting method (PLT-F). Clinically significant Hgb errors were defined as a >1 g/dL difference between the paired Hgb measurements. To account for the broader range of WBC count values, WBC count errors were defined by the simultaneous presence of an absolute difference of >2,000/uL and a relative difference of >10% between the two results. Results Despite coefficients of variation of