الفهرس 
Automated Hematology Analyzers
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Abstract
Complete blood count with leukocyte differential count
is one of the first quantitative methods for blood testing, and
for some time has been the most widely used of tests in clinical
settings. Therefore, validation of results from a hematology
analyzer has become an item of special importance that
reflects the quality of laboratory work and directly influencing
patient’s clinical conduct. To increase the quality of complete
blood count results provided by the laboratory, it is necessary
to assess the analytical performance of hematology analyzers
so as to ensure that the obtained results are the most reliable
possible.
In July 1981, Clinical and Laboratory Standards
Institute (CLSI) developed a proposed standard for evaluation
of automated and semiautomated hematology instruments for
their capability to perform an acceptable leukocyte differential
count (H20-P). In March 1992, CLSI published the first
edition of the approved standard (H20-A). In January 2007 the
second edition of the standard (H20-A2) was published.
The standard focuses on white blood cells found in
blood films and presents a detailed description of an
acceptable manual-visual leukocyte differential count which
serves as the reference for the instrumental differential counter. The standard outlines the types of abnormalities for
inclusion as well as a statistical method for determination of
the performance of the test method in both qualitative and
quantitative abnormalities.
Coulter LH 750 hematology analyzer is a fully
automated hematology analyzer designed to improve
workflow efficiency for high-volume laboratories through
elimination of preanalytical sample preparation and sorting as
well as reduction of postanalytical manual confirmation of
results. Coulter® LH 750 hematology analyzer is equipped
with the most advanced technologies available to improve
overall laboratory efficiency, while maintaining the highest
degree of testing accuracy.
The aim of the present work is to evaluate the leukocyte
differential count of Coulter LH 750 in hematology laboratory
in Ain Shams University Hospital as regard accuracy and
precision. Following CLSI H20-A2 approved standard,
manual leukocyte differential count was used as the reference
method for evaluation of the instrument analytical
performance and testing the manufacturer claims.
The study samples were routine inpatient and outpatient
samples from all hospital departments except for Hematology
Oncology Department which has a dedicated laboratory.
A total of 400 samples were selected randomly from
daily work load over a period of 3 months including 200 samples with normal leukocyte differential count and 200
samples with abnormal leukocyte differential count.
Automated complete blood counts with leukocyte differential
counts were performed using Coulter LH 750 hematology
analyzer. Two blood films were made for each sample and
stained by Leishman stain followed by 200 cells leukocyte
differential count per slide each by a different examiner or on
two occasions by one examiner. This counting was done
blindly (without knowing the results generated by the
analyzer).
Cells counted manually were categorized into 5 main
categories: neutrophils, lymphocytes, monocytes, eosinophils
and basophils. Immature granulocytes and variant
lymphocytes were also counted. Immature granulocytes were
added to the neutrophils category while the variant
lymphocytes were added to the lymphocytes category.
The mean of the manual leukocyte differential count
was calculated for each cell type in each sample. The total
mean of all samples was calculated for each test group;
normal, abnormal and total samples. Deming regression
analysis, Pearson’s coefficient of correlation and comparison
of the mean difference for each cell type of each sample with
the manufacturer specification were done.
Precision testing was done at two levels; within-run
precision and between-run precision. Within-run precision
was done by running a sample 20 times in a single run.Between run precision was done by running quality control
material each day for 20 successive days. The mean,
coefficient of variation and the 2 SD were calculated for each
cell type.
Correlation study revealed highly significant positive
correlation between the Coulter® LH 750 results and the
reference manual differential results for neutrophils,
lymphocytes, monocytes and eosinophils count in the
abnormal and total test groups but not in the normal test group
in which correlation was suboptimal. As regard basophils,
correlation study revealed a significant difference between the
two methods for which this type of statistical analysis has no
statistical validity.
Comparison of the mean difference for each cell type
with the manufacturer specifications for accuracy revealed
that the manufacturer specifications were met for all cell types
in the three test groups.
Within-run precision testing revealed imprecise
monocytes count by the instrument when compared with the
manufacturer specification or with ¼th total allowable error.
Neutrophils coefficient of variation was well within the ¼th
total allowable error, however it didn’t meet the manufacturer
specification.
There are no specification for between-run precision
published by the manufacturer, however comparing the total analytical variation for each cell type with 1/3rd total allowable
error revealed imprecise monocytes, eosinophils and basophils
count. The total analytical variation of other cell types was
within 1/3rd total allowable error. However they were
clinically accepted..