Three Cases of Pseudoeosinophilia Associated with Malaria Determined in the Sysmex XE-2100 Automated Hematology Analyzer

Abstract

In Korea, the incidence of malaria has been increasing in the civilian population and in the areas previously considered as noninfected. Malaria can be suspected based on the patient's symptoms and the physical findings at examination. However, for a definitive diagnosis to be made, the malaria parasites or their components must be demonstrated by laboratory tests, which will take time and require expertise. Since general screening tests, such as a complete blood cell count, are always done for patients with a fever, it can be expected that the attention of laboratory hematologists drawn to any abnormalities found in automated hematology analyzers can help reduce delays in the diagnosis of malaria even if such a diagnosis was not initially considered. We report three cases of malaria that had thrombocytopenia and pseudoeosinophilia shown in the Sysmex XE-2100 (TOA Medical Electronics, Kobe, Japan) automated hematology analyzer. It is feasible that the pseudoeosinophilia presented as a result of hemozoin-containing white blood cells may contribute to the diagnosis of malaria, especially for patients unsuspected of the disease.

Laboratory Diagnosis of Malaria: Comparison of Manual and Automated Diagnostic Tests

“…This can be attributed to the presence of extracellular pigment and RBC lysis which are reflected in that area [28]. Pseudoeosinophilia by machine compared with manual differential count was observed in 6.25% cases which is comparatively lower than previous report of 39% of cases of pseudoeosinophilia [16, 29]. …”

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.…”

“…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 haematology analysis to diagnose malaria

“…In South Korea, two case series, one with sixteen [52] and the other with three [53] P. vivax -infected patients, reported spuriously elevated eosinophil counts (pseudoeosinophilia) and abnormalities in the DIFF scatter-plot consisting of additional blue, red or gray-coded grouped events, and a fusion of both neutrophil and eosinophil groups (Figure 4) [52,53]. Later, two studies in a malaria-endemic region in South Korea evaluated pseudoeosinophilia (>5% difference between the automated and manual eosinophil count) and DIFF scatter-plot abnormalities for P. vivax diagnosis against thick film [54], or against thick film and real-time polymerase chain reaction (RT-PCR) [55] (Table 4).…”