A-156 Comparison of blast and variant lymphocyte flagging between the Alinity hq from Abbott and XN-1000 from Sysmex
Authors: Sun L , Dang T , Mulumba H , Rongey C 
Published: October 2024

Abstract

Background
Blast cells are immature white blood cells (WBC). The presence of blasts in the peripheral blood may be associated with certain diseases such as myelodysplastic syndrome and acute myelogenous leukemia. Variant lymphocytes (i.e., reactive lymphocytes, atypical lymphocytes) are WBCs produced by the immune system in reaction to infections caused by pathogens such as Epstein-Barr virus, cytomegalovirus, etc. It is clinically useful that the automated hematology analyzer is capable of flagging these cells. In this study, the blast (shown as ‘BLAST’ on the Alinity hq and ‘Blast/Abn Lympho?’ or ‘Blast?’ on XN-1000) and variant lymphocyte (shown as ‘VAR LYM’ on the Alinity hq, and ‘Atypical Lympho?’ on XN-1000) flagging was compared between the Alinity hq from Abbott and XN-1000 from Sysmex. Alinity hq has different sensitivity settings available for BLAST and VAR LYM flagging. In this study, the default setting for Alinity hq was used. For XN-1000, the Q-Flag default setting is 100. In this study, the setting was 120 for ‘Blast/Abn Lympho’ and 100 for “Atypical lympho?’.

Methods
Blood specimens were tested on the Alinity hq and XN-1000 analyzers. Two smears per specimen were made manually or by the Alinity hs slide maker stainer and read by two independent readers. The specimens showing any of the following flagging were included in the analysis: ‘BLAST’ on Alinity hq, ‘VAR LYM’ on Alinity hq, ‘Blast/Abn Lympho?’ or ‘Blast?’ on XN-1000, ‘Atypical lympho?’ on XN-1000. The flagging reports of these samples from both analyzers were compared to the smear review to determine if each analyzer's blast and variant lymphocyte flagging were true positive, false positive, true negative, or false negative.

Results
A total of 520 specimens were tested, yielding 41 specimens for blast flagging analysis and 80 specimens for variant lymphocyte flagging analysis. Due to the scarce availability of true positive samples from the manual review, true positive and false negative rate were not compared. For blast flagging using smear results of &gt;=1% or &gt;=5% as the positive criterion, Alinity hq yielded a 9.8% (=4/41) false positive rate and 87.8% (=36/41) true negative rate. XN-1000 yielded a 75.6% (=31/41) false positive rate and 22.0% (=9/41) true negative rate. For variant lymphocyte flagging using smear results of &gt;=5% as the positive criterion, Alinity hq yielded a 6.3% (=5/80) false positive rate and 92.5% (=74/80) true negative rate. XN-1000 yielded a 91.3% (=73/80) false positive rate and 7.5% (=6/80) true negative rate.

Conclusions
This study demonstrated that Alinity hq achieved a much lower false positive rate and much higher true negative rate for both blast and variant lymphocyte flagging when compared to the XN-1000. Manual blast and variant lymphocyte morphology classification is laboratory- and technician-dependent. Both analyzers allow different sensitivity/specificity levels to flag blasts and variant lymphocytes. Each individual laboratory should evaluate and choose the setting that is most suitable for their specific patient populations to obtain the desired flagging rate.