Erroneously elevated immature reticulocyte counts in leukemic patients determined using a Sysmex XE-2100 hematology analyzer

Abstract

The immature reticulocyte fraction (IRF) in peripheral blood, as determined by automated reticulocyte analysis, is calculated using the sum of medium and highly fluorescent reticulocyte numbers and provides information about erythropoietic activity in bone marrow. The purpose of this study was to investigate erroneously elevated IRF in leukemic patients, as determined using a Sysmex XE-2100 hematology analyzer (Sysmex, Kobe, Japan). Normal reticulocyte scattergram patterns show regions corresponding to reticulocytes located between matured RBCs and an upper particle (UPP) region, which show a continuum of nonseparated fraction. The UPP represents erythroblasts and some immature reticulocytes. As a control group, peripheral blood was taken from patients with benign hematologic diseases, and their reticulocyte scattergrams all showed a normal pattern; UPP values were all less than 100. However, the reticulocyte scattergrams of 5 of 11 leukemia patients showed abnormal patterns and displayed a gap between RBC and reticulocyte regions. Three patients showed a flag with a message such as "RET Abn Scattergram". IRF results were elevated in these five patients, and their UPP values were above 100. For the remaining six leukemia patients with a normal reticulocyte scattergram pattern, immature reticulocytes were not markedly increased, and UPP values were less than 100. The findings of the present study demonstrate that IRF results may be erroneously elevated in leukemia patients and indicate that hematologists should examine reticulocyte scattergrams and UPP values carefully.

Spurious reticulocyte profiles in a dog with babesiosis

“…But, in such cases, the atypical fluorescent cells are in the HFR, where 66% HFR reticulocytes were detected on an extended reticulocyte scattergram as an isolated cluster to the right of the normal location of HFR cells, and WBC can display young reticulocyte‐like fluorescence leading to an erroneous estimation of the HFR reticulocyte count . Leukemic cells were speculated to stain less intensely with polymethine than normal leukocytes and thus be spuriously identified as reticulocytes . More similar to our case, an erroneously high IRF was reported in a cases of high intra‐erythrocytic parasitemia in human malaria …”

“…In our case, an abnormal isolated reticulocyte cluster was found at the location of LFR cells (73.8%) and MFR (22.6%). Other cases with abnormal reticulocyte profiles have been described in cases of canine and human acute myeloid and lymphoid leukemia, and in human beings with malaria . In leukemia, the discrepancy has been proposed to be due to leukemic cells and cell fragments .…”

Analytic errors in Sysmex‐generated hematology results in blood from a dog with chronic lymphocytic leukemia

“…In contrast, leukemic cells appeared larger compared to RBC in microscopic evaluation and were correctly excluded from the RBC‐I count, mostly due to their larger size. The discrepancy between the size of pseudoreticulocytes and neoplastic cells would support the hypothesis that these elements could have been fragments or nuclei of leukemic cells, as previously suggested in human medicine . A similar interference between WBC and RET counts was also reported in a dog with acute leukemia, where cytoplasmic fragments of leukemic cells were recognized in the blood smear .…”

Correction of Pseudoreticulocytosis in Leukocytosis Samples Using the Sysmex XE-2100 Analyzer Depends on the Type and Number of White Blood Cells

“…Abnormal numbers of WBCs, WBC fragments, nucleated RBCs, giant platelets, and several other factors have been reported to lead to inaccurate gating of RBCs and are hence regarded as possible factors interfering with automated methods for reticulocyte analysis [16-19]. In leukemia patients, erroneously elevated immature reticulocyte counts obtained by using the XE-2100 analyzer have also been reported [14]. In this study, reduction of the WBC counts by simple dilution with an isotonic solution was able to address the abnormal scattergrams.…”

“…The fluorescence intensity is also used to segregate the reticulocyte population into 3 fractions - low, medium, and high fluorescence; the sum of the medium and highly fluorescent reticulocytes represents the IRF [13]. Signals with fluorescence intensity between that of reticulocytes and WBCs represent the upper particle portion (UPP) [14]. …”