Immature Granulocyte Count on the New Sysmex Xn­9000: Performance and Diagnosis of Sepsis in the Intensive Care Unit

Introduction. The amount of immature leukocytes reflects marrow response to bacterial infection, and this may be quantified as the band or immature granulocyte (IG) count. The aim of this study was to analyze the IG count performance of the Sysmex XN-9000 hematology analyzer in intensive care unit (ICU) patients. Methods. 480 peripheral blood samples from adult patients admitted to the ICU (301 control, 119 sepsis and 60 septic shock) were analyzed with Sysmex XN-9000. Serum C reactive protein (CRP) was measured on Siemens ADVIA 2400. IG count in peripheral blood was determined either by XN-9000 or optical microscopy (OM). Agreement between the two methods was assessed with Pearson’s correlation, Passing-Bablok regression and Bland Altman bias. Diagnostic accuracy was estimated through ROC curves analysis. Sysmex XN-9000 imprecision and within-run precision were also evaluated. Results. Pearson’s correlation (r) relative to IG count, as absolute and percentage values, was 0.89 (p <0.0001) and 0.74 (p <0.0001), respectively, with a Bias of 0.22 and 1.69 respectively. The Area Under the curve (AUC) for the IG count for diagnosing sepsis was greater on XN-9000 than OM and equal to the serum CRP. The diagnostic accuracy of IG counts improves when taking into account the conventional criteria for diagnosing sepsis. Conclusion. IG count appears suitable and reliable when performed using XN-9000. Even if a modest overestimation was found, the diagnostic accuracy showed by IG analysis on XN-9000 may represent a valid alternative to OM count for diagnosing sepsis in ICU patients.