Sysmex Journal International
Performance Evaluation of Automated Leucocyte Counting in Cerebrospinal Fluid ( CSF ) by the XE-2100 Compared to Manual Counting
B. SCHROEDER＊１, F. HAUKAMP＊２, F.-J SCHMITZ＊１, C. WIENEFOET＊３ and J.LINSSEN＊３
*1 Institute of Laboratory and Transfusion Medicine
*2 Institute Neurological Clinic, Klinikum Minden
*3 Sysmex Europe & Sysmex Deutschland GmbH
Objectives : To evaluate the performance of automated leucocyte counting in CSF from neurological patients using the Sysmex XE-2100.
Methods : The number of WBC was determined in 226 fresh ( maximum 2h from collection ) CSF samples by microscopy ( reference method ) and by the XE-2100 WBC/BASO and DIFF channels. Validation included measurement of linearity, within-day imprecision, carryover, limit of detection and correlation with reference method. A truth table was made for non-pathologic samples at counts less than 5 WBC/µL and pathologic samples greater than 4 WBC/µL for the XE-2100 and the reference method. Additionally PMN ( neutrophils + eosinophils + basophils ) and MN cell ( monocytes + lymphocytes ) differential counts were compared ( only n=30 ) with the microscopy cytopreparations.
Results : Within-day imprecision of the XE-2100 DIFF channel and with the manual method showed nearly the same results, 46 % and 37%, for extremely low WBC counts ( 2 cells/µL ). For higher WBC counts the DIFF channel is superior to the manual method
( WBC approximately 50/µL, 9% and 15%; WBC approximately 500/µL, 4% and 9% ). The within-day imprecision for the DIFF channel is superior to the WBC/BASO channel. Linearity and carryover showed excellent results for all channels. The XE-2100 counts showed excellent correlation with the microscopy reference counts in the range 0-3,000 WBC/µL ( DIFF channel: R2=0.985; WBC/BASO channel: R2=0.883 ). In the range lower than 50 WBC/µL however, the DIFF channel ( R2=0.870 [n=201] ) again showed a good correlation with the microscopy reference method, but, in contrast, the WBC/BASO channel showed no correlation ( R2=0.06 [n=201] ).The truth table showed that the DIFF channel is superior to the WBC/BASO channel particularly at a decision point of > 4 WBC/µL.The differentiation of WBC into PMN cells and MN cells with the DIFF channel give respectively R2=0.893 and R2=0.850, but only with 30 samples.
Conclusions : Determination of the WBC count in CSF using the DIFF channel of the XE-2100 is highly correlated to the microscopic reference method. Especially no false normal ( 0-4/µL ) WBC counts were found, so it is unlikely that a pathologic pleocytosis has been missed. Some false positive results were obtained ( 3% ). It is important for the supervising doctor to be aware of this for interpretation of the data. From a clinical point of view, however, the automated CSF count quality in the DIFF channel of the XE-2100 is absolutely sufficient for competent patient treatment.
The differential count ( PMN and MN ) appears promising, but more samples must be studied.
Cerebrospinal Fluid, Leukocyte Count, Automated Hematology Analyzer, XE-2100, WBC Count DIFF Channel