Pseudoeosinophilia associated with malaria infection determined in the Sysmex XE-2100 hematology analyzer

Abstract

Hemozoin is known to be an end product of hemoglobin digestion by the malaria parasite. Hemozoin is a birefringent crystal, and thus hemozoin-containing white blood cells (WBCs) may show the atypical light scattering pattern. The purpose of this study was to investigate pseudoeosinophilia associated with malaria infection using a Sysmex XE-2100 hematology analyzer (Sysmex Corporation, Kobe, Japan). The study group included 16 patients with malaria infection. Of these, 38% showed erroneously high eosinophil counts and atypical eosinophil distributions in the WBCs scattergram, which was due to the presence of hemozoin-containing neutrophils. In two patients, their erroneously high eosinophil counts declined as the parasitemia decreased with treatment. In conclusion, hematologists should consider the possibility of pseudoeosinophilia as a result of hemozoin-containing WBCs and confirm the WBC differential count by microscopy in cases of malaria infection.

Design of Malaria Diagnostic Criteria for the Sysmex XE-2100 Hematology Analyzer

“…4,21 More recently, using the XE-2100 analyzer, two case series in South Korea, one with 16 and one with 3 P. vivax -infected patients, described pseudoeosinophilia and abnormal granulocyte-coded events in the DIFF scatterplot in approximately 38% of samples. 9,10 In 2008, Huh and others 5 in South Korea compared these two findings against thick-film malaria diagnosis in 144 samples of P. vivax -infected patients and in 319 samples from febrile patients, reporting a sensitivity of 69.4% and a specificity of 100%. 5 Other small case series have described similar findings 6,24 in P. vivax infected samples, and a case describing an elevated reticulocyte/IRF ratio and an increase in highly fluorescent lymphocyte-coded events in the DIFF scatterplot [DIFF(II) area] in a P. falciparum -infected patient 25 has been published by the Sysmex Corporation.…”

“…5,9 Huh and others 5 found that ≥ 5% pseudoeosinophilia in P. vivax -infected samples had a sensitivity of 38.9% and a specificity of 100%. We found that the optimal P. vivax -diagnostic pseudoeosinophilia was 20.9% and had an accuracy of 60.5% (95% CI = 51.1-69.9%).…”

“…8 For the Sysmex XE-2100, two case series reported a gap between the manual and automated eosinophil counts (pseudoeosinophilia) and abnormal granulocyte-coded events in the DIFF scatterplot used for white blood cell (WBC) separation based on fluorescence versus side-scatter signals in samples from Plasmodium vivaxinfected patients. 9,10 Later, Huh and others 5 found that the two previously reported abnormalities, compared with thick film, had a sensitivity of 69.4% and a specificity of 100% for P. vivax diagnosis. These findings suggest the potential clinical utility of malaria detection by the XE-2100.…”

Automated Detection of Malaria-Associated Pseudoeosinophilia and Abnormal WBC Scattergram by the Sysmex XE-2100 Hematology Analyzer: A Clinical Study with 1,801 Patients and Real-Time Quantitative PCR Analysis in Vivax Malaria-Endemic Area

“…[1][2][3][4][5][6] Recent studies from South Korea investigated pseudoeosinophilia and abnormal white blood cell (WBC) scattergrams of vivax malaria-infected patients on a Sysmex XE-2100 hematology analyzer (Sysmex Corporation, Kobe, Japan). 7,8 Because the sensitivity and specificity of these methods were apparently high, its application to early detection can lead to a significant reduction in patients' morbidity and mortality. 2,8 Previous studies had limitations of a rather small patient number and their inaccurate evaluation of parasitemia.…”

“…2,11 Several authors have described pseudoeosinophilia or abnormal WBC scattergrams as a result of hemozoin-containing neutrophils using the Sysmex XE-2100 analyzer. 7,8,12 The Sysmex XE-2100 analyzer differentiates eosinophils from neutrophils based on side light-scattering differences. The neutrophils may show considerable side light scattering because of the birefringent character of hemozoin, and therefore, hemozoin-containing neutrophils may be incorrectly classified as eosinophils or two atypical eosinophil populations and two neutrophil populations.…”