Contribution of automated hematology analysis to the detection of apoptosis in peripheral blood lymphocytes

Mindray BC-6800 haematological analyser: 3D-DIFF scattergram usefulness in infectious mononucleosis diagnosis

INTRODUCTION

3D-DIFF scattergram of the Mindray BC-6800 haematological analyser shows morphological abnormalities and lymphocyte cluster splitting related to the presence of reactive lymphocytes. This study aims to assess whether these cytographic changes are useful in detecting both activated and apoptotic lymphocytes, leading to an improvement in the laboratory diagnostic process of infectious mononucleosis.

METHODS

Two hundred three samples with modified shape and doubled lymphocyte cluster of DIFF scattergram (study group) were divided into two different subgroups: with and, respectively, without serological evidence of ongoing IM. Activated and apoptotic cells in peripheral blood were counted by light microscopy or gating in the instrumental dot plots. Values of apoptotic cells counted by microscopy were compared with those resulting from gating.

RESULTS

Samples with both shape change and doubled lymphocyte cluster had serological profiles according to the diagnosis of ongoing infectious mononucleosis. Blood smears review was positive for reactive lymphocytes in all 112 samples (100%). An underestimation of apoptotic cell count by light microscopy compared with the gating in the instrumental scatterplot was also observed (96 out of 112, 85.7%).

CONCLUSION

The additional lymphocyte cluster was significantly associated with activated and apoptotic lymphocytes in samples with serology suggesting ongoing infectious mononucleosis. Considering the significance of clue for infectious mononucleosis assigned to the apoptotic lymphocytes, a specific flag such as "apoptotic cells?" could be associate with the related cluster. Such a flag could be used for dedicated rules for smears review, thus increasing infectious mononucleosis detection in laboratories that do not usually practise instrumental cytograms observation.

Detection of Apoptotic Lymphocytes Through Sysmex XN-1000 As a Diagnostic Marker for Mononucleosis Syndrome

BACKGROUND

The infectious mononucleosis (IM) includes clue elements, apoptotic and atypical lymphocytes. In IM, the evaluation of dot plot provided by Sysmex XN-1000 analyzer revealed a stretched lymphocytic cluster, white cell differential channel (WDF), on cytogram.

METHODS

In this study, we analyzed 698 samples that include 39 IM, 76 chronic lymphoproliferative disorders, 25 nonclonal lymphocytosis, and 40 healthy donors. Five hundred eighteen samples with other diseases or interference were evaluated. The algorithm was validated on 40,000 files that were received from internal database of Sysmex-Dasit.

RESULTS

The analysis of flow cytometry standard (FCS) files in WDF channel and presumed apoptotic lymphocytes counts on side scatter/forward scatter (SSC/FSC) and SSC/SFL (where SFL is side fluorescence) dot plot revealed excellent correlation among apoptotic cells on peripheral blood smear (R(2)  = 0.79 and 0.75). There was a variation of positional parameters in lymphocyte clusters WX, WY, and WZ. If WX-SSC > 500 and WY-SFL > 1,000 and WZ-FSC > 700, specificity equals to 99% and sensitivity equals to 100%. If nucleated red blood cell (NRBC) <0.03 × 10(3) /μl, specificity equals to 100%. In received files, positives were 1% adding the simultaneous presence of a percentage of events in the two gates relating to the apoptotic lymphocytes of 1.2% of WBC.

CONCLUSION

On Sysmex XN-1000, dot-plot observation allowed immediate detection of IM. Meanwhile, an algorithm based on the parameters on these plots can be calculated with excellent performance.

Apoptosis in Infectious Mononucleosis: Its Detection with the Beckman Coulter GenS Hematology Analyzer

This article describes the potential of the Beckman Coulter GenS hematology analyzer for detecting and quantifying the phenomenon of elevated apoptosis found during the incubation at 37 degrees C of samples containing CD45RO+ reactive T-lymphocytes from patients with infectious mononucleosis (IM). Visual detection was carried out with the GenS DF1 scattergram (volume/scatter), and the means and SDs of lymphocyte positional parameters (volume, scatter, and conductivity) were recorded from the instrument research screen before and after samples were incubated in an oven for 4 hours. Thirty-one IM samples were analyzed, and the results obtained after sample incubation showed a mean reduction in lymphocyte volume of 34%, a 3.9% increase in scatter, and a 4% increase in conductivity. A new cluster of cells consistent with apoptotic lymphocytes appeared in the GenS DF1 scattergram. May-Gr-Giemsa staining and extended manual counting of the samples carried out at the same time to validate and quantify the apoptosis of the analyzed samples detected a significant increase in apoptotic cells from 1.2% (range, 0%-3%) to 8.37% (range, 1%-39%) after incubation. The same process was used to evaluate a control group of patients, and the possible interference of platelet aggregation and erythroblasts (nucleated red blood cells) in GenS apoptosis quantification was investigated. The final results showed that the appearance of the apoptotic cluster in the GenS DF1 scattergram occurred in 96.8% of the IM cases, although this phenomenon is apparently nonspecific because similar clusters appear in other pathologies, such as viral infections (hepatitis, cytomegalovirus, and acquired immune deficiency syndrome). Additional quantitative studies of apoptosis kinetics indicated that at least 4 hours of incubation are necessary. This finding has directed an investigation of apoptosis-inducing drugs (camptothecin, theophylline) to reduce incubation time and thereby enhance the practical application of automated apoptosis detection in the diagnosis of IM and other diseases in which the phenomenon of apoptosis occurs.

Comparison of automated haematology analysers for detection of apoptotic lymphocytes

Automated haematology analysers can rapidly provide accurate blood cell counts and white blood cell differentials. In this study, we evaluated four different haematology analysers for the detection of apoptotic lymphocytes in peripheral blood: MAXM A/L Retic, H*2, Cell-Dyn 3500 and NE-8000. With the MAXM A/L Retic haematology analyser, the apoptotic lymphocyte cluster appeared below the original lymphocyte cluster on the volume/DF1, and to the right under the original lymphocyte cluster on the volume/DF2 scattergrams. With the H*2 haematology analyser, the apoptotic polymorphonuclear lymphocytes produced a higher lobularity index on the BASO channel. With the Cell-Dyn 3500 haematology analyser, the apoptotic lymphocyte cluster appeared to the right side of the original lymphocyte cluster on the 0D/10D scattergram and to the left side of the polymorphonuclear cluster on the 90D/10D scattergram. With the NE-8000 haematology analyser, the apoptotic lymphocyte cluster was not distinguishable. Thus, apoptotic lymphocytes are readily detected on scattergrams generated by selected haematology analysers.

Diagnosis of atypical cases of infectious mononucleosis

The variable manifestations of infectious mononucleosis rarely cause clinicians to suspect primary Epstein-Barr virus or cytomegalovirus infection; consequently, costly diagnostic tests and unnecessary treatments are undertaken. Seventeen cases of clinically atypical and 11 cases of clinically typical infectious mononucleosis were diagnosed through screening for atypical and apoptotic lymphocytes in the peripheral blood samples by means of an automated hematologic analyzer. Atypical and typical cases did not differ significantly with respect to peripheral white blood cell counts; percentages of lymphocytes, atypical lymphocytes, CD4(+) lymphocytes, human leukocyte antigen--DR positivity in CD3 lymphocytes, or apoptotic cells in blood smear after incubation; or levels of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase. Only the percentage of CD8(+) lymphocytes was significantly higher in patients with typical infectious mononucleosis than it was in patients with atypical infectious mononucleosis. Because certain atypical cases of infectious mononucleosis display laboratory abnormalities that are characteristic of typical infectious mononucleosis, enhanced awareness can help in the diagnosis.