Introduction: Eosinophilia in most of cases is due to result of reactive process, but it could also be a part of hematopoietic malignancy. Blood smear review is important for confirmation of eosinophilia presence, as well as for morphology and quantitative assessment of eosinophil, and other cell lines that are needed for further eosinophilia work up. To distinguish pseudo-eosinophilia from eosinophilia, 3 clinical cases were identified at Fatmawati Hospital, Jakarta, Indonesia.
Case: Three patients with high eosinophil count were found in October 2018. K3EDTA bloodwas used for complete blood count (CBC) with ADVIA 2120i hematology analyzer and for blood smear. Wright stained smear and data from the analyzer were analyzed by a pathologist, and revealed that first patient had true eosinophilia while the two others had pseudo-eosinophilia.
Morphology evaluation showed that the second patient had acute myeloid leukemia (AML) with dysplastic neutrophil and the third one had acute promyelocytic leukemia (APML). Scattergram of PEROX chanel in first case showed distinct eosinophil region which was larger than normal, while in the rest cases; the cell population in the eosinophil region was seen to be united with the population from the neutrophil region and counted as eosinophil. In the second case, the scattergram abnormality was result of abnormal MPO activity and light scatter of dysplastic neutrophils, whereas in the third case it was due to abnormal promyelocytes population with high peroxidase activity. Data from normal patient was provided for comparison.
Conclusion: Pseudo-eosinophilia can be found in various hematologic disorders, and can hamper the accuracy of an automated differential count. This report underlines the need for slide review when eosinophilia is found, as suggested by The Consensus Group. Scattergram evaluation from a cytochemical automated analyzer gives good clue whether eosinophilia found in the automated differential count is a true one or pseudo-eosinophilia.