Evaluation of the Beckman-Coulter GEN-S hematology analyzer

ISLH
Laboratory Hematology 4:264–268
© 1998 Carden Jennings Publishing Co., Ltd.
Official Publication
Evaluation of the Beckman-Coulter ® GEN-S
hematology analyzer
E. GRIMALDI, F. SCOPACASA
Department of Laboratory Medicine, University Federico II, Naples, Italy
ABSTRACT
The Beckman-Coulter GEN-S, a new generation hematology
analyzer capable of providing a complete blood count, a five-part
differential leukocyte count, and a reticulocyte count, was evaluated
on the basis of the H20-A protocol of the National Committee
for Clinical Laboratory Standards and its performance compared
with the Bayer-Technicon H-2 analyzer that is routinely
used in our laboratory. A lipid interference experiment was also
performed. Linearity, carryover, and precision were all within the
limits established by the manufacturer, and satisfactory agreement
with the H-2 analyzer was found. The evaluation of the leukocyte
differential indicates an excellent correlation between the manual
reference method for neutrophils and lymphocytes
(r = 0.981 and 0.971, respectively), a good correlation for monocytes
and eosinophils (r = 0.820 and 0.883, respectively), and a
poor correlation for basophils in samples with low counts—for
basophil counts higher than 1% we found an improvement in the
correlation. The leukocyte differential flag sensitivity assessment
shows higher specificity (96%) than sensitivity (85%) and a high
efficiency (93%). In the lipid interference experiment, only
hemoglobin determination has been significantly influenced on
the GEN-S. Lab Hematol 4:264–268, 1998
KEY WORDS: Blood cell counter · Accuracy ·
Precision · Interference
INTRODUCTION
The GEN-S (Beckman-Coulter, Miami, FL) is a new generation
fully automated hematology analyzer that can provide the laboratory
with up to 34 blood count parameters: a complete blood
count (CBC), a five-part differential leukocyte count (DLC), a
complete reticulocyte count, and an automated CD4/CD8 count.
Moreover, when abnormal leukocytes are present, the system generates
different flags.
Address correspondence to Ernesto Grimaldi, MD, Dipartimento Assistenziale
di Medicina di Laboratorio, Policlinico Universitario Federico II, Via S. Pansini
5, 80131 Napoli, Italia.
Received 4 September 1998; accepted 3 November 1998
Over a 3-month period we evaluated, on the basis of the H20-A
protocol of the National Committee for Clinical and Laboratory
Standards (NCCLS) [1], the CBC and DLC performance of the
GEN-S in comparison with a reference fully automated hematology
analyzer in use in our laboratory, the Bayer-Technicon H-2 (Bayer-
Technicon Instruments, Tarrytown, NY), and with the reference
manual method (DLC performance only). We also evaluated the
clinical sensitivity and the lipid interference on both instruments.
MATERIALS AND METHODS
System Description
The GEN-S analyzer uses the Coulter Volume, Conductivity,
Scatter (VCS) technology to probe hydrodynamically focused cells
[2]. Volume measurement is performed using the Coulter principle
of electrical impedance.
The high frequency conductivity provides information about
cell size, internal structure, and density. A helium-neon laser and a
multiple-angle light scatter provide information about a cell’s internal
structure, granularity, and surface morphology. VCS technology
has proven effective on the Coulter STKS and MAXM analyzers
[3,4]. The GEN-S refines this technology through the use of the
IntelliKinetic (Beckman-Coulter) application. This hardware and
software system intelligently manages variations in the ambient laboratory
temperature through automatic adjustments of reagent
reaction temperature, exposure time, and delivery volumes.
Enhancement in instrument electronics works with the IntelliKinetic
application to provide better data signals for the system algorithm
to analyze. Collected data are analyzed by Coulter AccuGate
software (version EASE 2, Beckman-Coulter), which contains
adaptive statistical tools that assist in delineating overlapping populations
including new suspect flags (e.g., Ly blast for Lymphoblast
suspect) and additional “research use only” parameters. DLC data
can be presented in a multidimensional format.
Blood Samples
The evaluation of the instrument was performed by analyzing
blood specimens from routine samples obtained after having
received each patient’s written informed consent. All samples were
collected in evacuated 3.5-mL tubes containing tripotassium ethylenediaminetetraacetic
acid (K 3 EDTA) and tested within 2 hours of
drawing the blood. All samples were analyzed in parallel on the
GEN-S and H-2 analyzers.
264

Beckman-Coulter GEN-S 265
TABLE 1. Percent carryover with the Beckman-Coulter ® GEN-S
analyzer
Parameter
WBC RBC Hb PLT
Carryover (%) 0.5 0.3 0.4 0.01
Hb, hemoglobin; PLT, platelet; RBC, red blood cell count; WBC, white blood
cell count.
Carryover Assessment
Carryover assessment was performed according to the
Broughton method [5]: a high sample was tested three consecutive
times (H1, H2, H3) and followed by a low-sample testing performed
three consecutive times (L1, L2, L3). The percentage of
carryover for each parameter was calculated using formula 1:
[(L1 – L3)/(H3 – L3)] 100
Linearity
Linearity was evaluated by analyzing serial dilutions of five specimens
in platelet-free autologous plasma [6]. Results were evaluated
in accordance with the International Council for Standardization in
Hematology (ICSH) recommendations [5].
Imprecision
For a between-batch imprecision study, 20 samples, in triplicate
and in three consecutive batches, were analyzed; within-batch
imprecision was evaluated by analyzing 20 samples in triplicate in
the same batch. Results were expressed as mean, standard deviation
(SD), and percent coefficient of variation (%CV).
Comparability
Selected on the basis of the recommended ICSH range of values
[7], 120 blood samples were analyzed side by side using the GEN-S
and the H-2 analyzers. Instruments were calibrated according to
the manufacturer’s guidelines. Measured white blood cell count
TABLE 2. Linearity of the Beckman-Coulter ® GEN-S analyzer
Parameter SI unit Range r Intercept Slope
WBC 10 9 /L 0.15–100 0.999 –0.002 0.998
RBC 10 12 /L 0.17–7.0 0.999 –0.023 1.000
HB g/dL 0.50–20.0 0.999 –0.066 1.000
PLT 10 9 /L 6.20–1000 0.999 –2.200 1.002
(WBC), red blood cell count (RBC), hemoglobin (Hb), mean cell
volume (MCV), platelet (PLT), and DLC parameters (absolute values)
were compared by linear regression analysis, and correlation
coefficients (r) also were calculated.
Also, 112 blood samples were compared with manual DLC
(percent values). All films were examined independently by four
experienced technologists, results compared by linear regression,
and correlation coefficients calculated [1].
Clinical Sensitivity
As recommended in the NCCLS guidelines [1], the result of
microscopic examination was used to classify a sample as normal or
abnormal; therefore, differential results of 112 samples were divided
into the following categories:
• true-negatives: normal samples leading no instrument flags
• true-positives: abnormal samples leading instrument flags
• false-positives: normal samples leading instrument flags
• false-negatives: abnormal samples leading no instrument flags
The results were analyzed following the method of Galen and
Gambino [8].
Interference Study
Lipid interference was evaluated in 10 blood samples with
increasing amounts of Intralipid (Pharmacia AB, Uppsala, Sweden)
(soya’s lipids). They were analyzed side by side with the two instruments
and each test was performed in triplicate. Results were
expressed as the mean value of three determinations. The lipid concentration
was measured as triglycerides.
TABLE 3. Within- and between-batch precision observed with the Beckman-Coulter ® GEN-S (n=20)
Within-batch
Between-batch
Parameter SI unit Mean SD %CV Mean SD %CV
WBC 10 9 /L 19.9 0.245 1.23 9.0 0.145 1.64
RBC 10 12 /L 4.12 0.055 1.32 5.39 0.07 1.31
Hb g/dL 12.8 0.080 0.64 16.5 0.13 0.78
MCV fl 87.3 0.375 0.43 88.9 0.25 0.28
PLT 10 9 /L 424.0 7.970 1.88 231.0 6.045 2.62
NE # 12.5 0.18 1.43 4.9 0.1 2.06
LY # 3.1 0.115 3.68 2.5 0.08 3.19
MO # 3.0 0.09 3.0 0.8 0.07 4.62
EO # 1.3 0.07 5.55 0.7 0.025 3.12
BA # 0.7 0.15 21.4 0.36 0.08 22.2
BA, basophil; EO, eosinophil; LY, lymphocyte; MCV, mean cell volume; MO, monocyte; NE, neutrophil.

266 E Grimaldi and F Scopacasa
TABLE 4. Comparability test between the Beckman-Coulter ® GEN-S
and the Bayer-Technicon ® H-2
Parameter SI unit Intercept Slope r
WBC 10 9 /L –0.1288 1.034 0.998
RBC 10 12 /L –0.0602 0.995 0.997
Hb g/dL –0.2836 0.988 0.998
MCV fL –4.0571 1.019 0.990
PLT 10 9 /L 5.930 0.912 0.985
Neutrophils # –0.048 1.072 0.997
Lymphocytes # 0.0418 1.031 0.996
Monocytes # 0.0282 1.206 0.996
Eosinophils # 0.0176 0.974 0.975
Basophils # a 0.0338 0.0338 0.571
Basophils # b 0.940 0.290 0.910
a Range of values: 0–10010 9 /L.
b Range of values: 100–100010 9 /L.
RESULTS
Carryover
Carryover data for WBC, RBC, HB, and PLT are presented in
Table 1. The results of high to low carryover testing were 0.999 for all
CBC parameters evaluated, also in a very low range. We also found
that the unflagged percentage of WBC differential count results
were reproducible and linear down to a level of 0.1510 9 /L WBC
count (data not shown).
Imprecision
We found good reproducibility for within- and between-batch
studies for all parameters, including CBC and WBC differential
counts (Table 3). For basophils, we found a high %CV (>20%).
TABLE 5. Results of inaccuracy assessment: Comparison between the
Beckman-Coulter ® GEN-S and the manual differential leukocyte
count
Parameter SI Unit Intercept Slope r
Neutrophils % 0.832 0.995 0.981
Lymphocytes % 1.446 0.985 0.971
Monocytes % 0.630 0.878 0.820
Eosinophils % 0.399 0.915 0.883
Basophils % a 0.360 –0.009 –0.020
Basophils % b 1.786 0.819 0.931
a Range of values: 0–1%.
b Range of values: 1–10%.
Comparability
The GEN-S gave CBC and DLC results that compared very well
with data obtained by the H-2 (Table 4). The basophil results
showed poor agreement (r = 0.571) between the two instruments in
the low range of counts and good agreement for high basophil counts
(r = 0.910). The results of correlation and linear regression analyses
between the GEN-S and a manual differential show excellent correlation
for neutrophils and lymphocytes, good correlation for monocytes
and eosinophils, and low correlation (low range of values 1% (n=25).
Clinical Sensitivity
Results of the instrument flagging assessment show that the
GEN-S performance was substantially higher for specificity (96%)
than sensitivity (85%) with an efficiency of 93%; whereas the H-2
showed specificity of 77%, sensitivity of 73%, and efficiency of
76% (Table 6).
Interference Study
A significant inaccuracy was observed in the Hb determinations
on both instruments starting from a lipid value of ≥450 mg/dL and
FIGURE 1. Interference by lipemic samples on hemoglobin
(HGB) determination. Both the GEN-S and the H-2
show significant overestimation (31 g/dL) starting from a
lipid value of triglycerides (TGL) 3450 mg/dL.
FIGURE 2. Interference by lipemic samples on RBC count.
RBC count is stable on both instruments up to a lipid value
(TGL) of 2500 mg/dL. With higher lipid concentration,
only the H-2 analyzer shows an RBC count overestimation.

Beckman-Coulter GEN-S 267
resulting in an Hb overestimation of ≥1 g/dL (Fig. 1). Conversely,
no interference was found on either instrument for the WBC or
DLC counts. RBC and PLT counts in lipemic samples (Figs. 2 and
3) were overestimated on the H-2 system, but only for high lipid
concentrations. No interference was found on the GEN-S.
DISCUSSION
The Beckman-Coulter GEN-S is an automated hematology analyzer
that provides a CBC and five-part DLC using improved VCS
technology with advanced software and hardware applications.
In our study, instrument reproducibility (between- and withinbatch
imprecision) results were satisfactory with the exception of
the basophil count. Furthermore, the instrument demonstrates
minimal carryover and good linearity.
For CBC and DLC, we have also found a good correlation with
the H-2 analyzer and with the reference manual differential for all
WBC subpopulations except for, in both cases, the basophils in the
low range of counts (0–10010 9 /L and 0–1%, respectively). In all
probability, the high basophil CVs and the poor correlation
between the two instruments were not due primarily to poor performance
of the analyzers’ WBC differential count, but to the low
number of basophils counted. Similarly, the low correlation with
the reference method may have been attributed to the low number
and irregular distribution of the cells in the peripheral blood films.
In fact, analyzing samples with high basophil counts yielded a dramatically
increased correlation coefficient, suggesting that an
increase in the number of cells used for automated differential
leukocyte counts is a prerequisite for improving basophil counting
performance by hematology analyzers.
An excellent correlation for monocytes was found with the H-2
analyzer (r = 0.996) and a modest one with the reference method (r
= 0.820). This result, which agrees with other reports [9,10],
appears to be due to artifact distribution for these cells during the
blood film preparation and to difficulties in differentiating small
TABLE 6. WBC flagging performance
Beckman-Coulter ® Bayer-Technicon ®
Gen-S
H2
Specificity (%) 96 77
Sensitivity (%) 85 73
Efficiency (%) 93 76
False-positive (%) 4 23
False-negative (%) 15 27
monocytes from large lymphocytes. Further studies will be performed
in which the GEN-S monocytes will be compared with differentials
generated by flow cytometry.
Like other automated hematology analyzers, the GEN-S generates
WBC flags when leukocyte abnormalities are present. The evaluation
of the instrument flags indicates a good sensitivity (85%)
and high specificity (96%) for these signals. The high efficiency of
flags (93%) is related to a high percentage of specimens correctly
classified. Although the analysis of flagging is still incomplete, this
study shows evidence that the sensitivity and specificity of the
GEN-S instrument are better than those of the H-2 analyzer.
In the lipid interference study, an expected significant inaccuracy
in Hb determination occurred on both instruments starting
from a lipid value of 3450 mg/dL. Very high lipid amounts (4800
mg/dL) showed no interference with the WBC, RBC, and PLT
counts performed by GEN-S. These data suggest the ability of the
GEN-S algorithm to discriminate high amounts of lipidic particles
and to exclude them from counts as well.
In conclusion, our evaluation data show that the GEN-S is a
precise screening device and its accuracy is at least comparable to
the Bayer-Technicon H-2. The results are linear to low counts, and
no significant carryover is observed. Additionally, we found that the
FIGURE 3. Interference by lipemic samples on PLT count. PLT count performed by the GEN-S is stable up to a lipid value (TGL)
of 4800 mg/dL. PLT count by the H-2 shows significant overestimation starting from a lipid value (TGL) of 1200 mg/dL.

268 E Grimaldi and F Scopacasa
ease of use contributes to the performance of the GEN-S, enhancing
its application in the clinical laboratory.
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