Granularity Index of the SYSMEX XE-5000 hematology analyzer as a replacement for manual microscopy of toxic granulation neutrophils in patients with inflammatory diseases

Background: When certain inflammatory processes occur, toxic granulation neutrophils (TGNs) appear in the blood showing prominent cytoplasmic granules. Currently, the granularity of TGNs is analyzed by manual microscopy of blood smears. The SYSMEX XE-5000 is an automated hematology analyzer, which can measure toxic granulation of TGNs by calculating the Granularity (GI) Index. In this study we investigated if the GI-Index is suitable as a parameter for the TGN granularity in inflammatory diseases. Methods: An evaluation of the toxic granulation neutrophil (TGN) granularity by manual microscopy, the GI-Index and the C-reactive protein (CRP) concentrations of 158 patients were determined. Blood samples from 40 healthy individuals were incubated with lipopolysaccharide (LPS) for in vitro kinetic measurements of the GI-Index. Furthermore, time course measurements of the GI-Index and CRP concentrations of 100 intensive care unit patients were performed. Results: The GI-Index correlated with the microscopic rating of TGNs (n = 158; r(s) = 0.839; p < 0.0001). When incubating the blood samples with LPS, the neutrophils displayed hypogranulation 30 min after incubation and a hypergranulation after 90 min. In vivo, the GI-Index indicated changes of the bacterial infection status 1 day earlier than the CRP concentration. The correlation of CRP and GI-Index varied between the patient cohorts (n = 158; r(s) = 0.836) (n = 100; r = 0.177), depending on the cause and extent of inflammation. Conclusions: The GI-Index is suited to quantify the granularity of TGNs. The GI-Index is an automated, standardized parameter available on a 24 h basis. We suggest that it replace the time-consuming, subjective and semiquantitative microscopic procedure.