SEED Hematology

Sysmex Educational Enhancement and Development

No 2 | 2017

Quality Control in Haematology

Quality control materials: the better you treat them, the more you can trust your haematology results

Key words:
Quality controls, quality materials, controls, internal quality control

Why is Quality Control so important? IQC is conducted by running one or more control materials
One vital part of quality assurance is the internal quality on the analysis system that is to be checked. The control
control (IQC), which is used to ensure day-to-day materials undergo an analytical procedure identical to that
consistency of an analytical process, helping to determine applied to patient samples. The results are plotted on
whether patient results are reliable enough to be released. control charts as described by Levey-Jennings, and those
Performing IQC also enables the laboratory to monitor and charts are interpreted in the usual fashion.
document the quality of its work. In most of the countries it
is required to perform IQC by national regulations. Sounds simple? Well, it’s not entirely simple. There are
factors that need careful consideration if the IQC system is
There are four main purposes of IQC: to represent a lab’s routine analytical operation adequately.
1. To monitor the complete analytical process.
2. To detect immediate errors that occur due to Requirements QC materials have to meet
a) a failure of the analytical system, Controls are materials that contain an established amount
b) adverse environmental conditions, or of the substance to be tested. Controls have to be tested at
c) operator performance; for example maintenance the same time period and in the same way as patient
procedures being carried out incorrectly samples. The purpose of the control is to validate the
3. To monitor the long-term test performance that may be reliability of the analysis system and to evaluate operator
influenced by changes in the performance of the performance and environmental conditions that might have
a) analytical system, an impact on the results. It is particularly critical to select
b) environmental conditions and appropriate control materials.
c) inter-operator variance.
4. To provide proof of an adequate long-term quality level
and to comply with regulatory requirements.
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The best materials for IQC are typical samples of the routine components that simulate cells, such as latex particles.
test materials, assuming that they are sufficiently stable for However, a microscopic white blood cell differential cannot
the purpose. Table 1 lists recommended properties of quality be accomplished with this material, as the white blood cells
control materials as per recommendations of the Hong Kong have been treated to enhance their stability. This means
Association of Medical Laboratories (HKAML) [1]. they will not stain to demonstrate the typical cell
morphology known from May-Gruenwald-Giemsa staining.
Additionally, it has to be taken into consideration that But regarding lysing and staining behaviour with the
control materials need to be different from calibrator analyser reagents, the stabilised cells only show small
materials [2]. differences to fresh blood cells. These differences are the
reason why the analyser uses a QC mode to produce and
Table 1 Recommended properties of a QC material display the measurement results.

1. It should resemble a human sample (blood, plasma, Serum,

CFS, etc). Sysmex control materials are ready to use. All controls are

2. The analyte concentration should be at medically significant delivered in vials with sufficient material for the control
levels. It should span the clinically important range of an period and are measured with the same measuring
analyte’s concentration
principle as patient samples.
3. The material matrix should be as much like human sample as
possible
For all diagnostic whole blood parameters Sysmex delivers
4. Constituents should be stable for a long period of time
controls in the low, normal and high analytical range and in
5. After the vial has been opened and material prepared it
should be stabile during the period of use order to check body fluid parameters, we provide two

6. The control material should be ready to use and require control levels.
minimal preparation

7. Convenient sizes of aliquots/vials can be prepared and vial- For the manufacturing of our haematology control
to-vial variability should be low
materials, we trust the well-known producer Streck Inc.
8. It should be reasonable priced ( optional) (Nebraska, USA), who is recognised worldwide as the leader
9. The control material should be tested in the same manner as in cell stabilisation. Streck’s core competence is the
patient samples
development of quality control materials that are tailored
to the customers’ needs.
QC materials from Sysmex
Manufacturing quality control materials for haematology is Transportation, storage conditions and shelf life
a challenge compared with controls for clinical chemistry if Sysmex haematology control materials are to be stored
all the points mentioned above are to be covered. Native with a closed cap at 2 – 8°C. A short-term increase in
cells naturally have a very limited survival rate. To extend a temperature, which may occur during transportation, does
cell’s life to a longer period, efficient stabilisation is needed. not affect the quality of the product. All haematology
Due to this, haematology quality control material is control materials must be protected from freezing. When
different from freshly collected patient samples. This means handled in this manner, the products are guaranteed stable
care must be taken to ensure the material has been used until the expiration date stated on the package and vials.
correctly when interpreting quality control results. Once the vials have been opened or sampled by cap
piercing, they will retain stability – depending on the
Sysmex control materials include stabilised human red blood product type – as stated in Table 2.
cells (RBC), white blood cells (WBC), and a platelet (PLT) and
nucleated red blood cell (NRBC) component in a
preservative medium. They are free from any artificial
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Table 2 Stability of Sysmex haematology controls

Control material Period of use Open vial stability

Eightcheck-3WP 84 days 7 days

e-Check (XS) 56 days 14 days

e-Check (XE) 56 days 7 days

XN-L Check 84 days 15 days

XN Check 56 days 7 days

XN-L Check BF 56 days 30 days

Preparation of XN-Class QC materials before

measurement
When storing and preparing quality control materials it is
important to carefully adhere to the manufacturer’s
instructions for storage and equilibrating.

1. Remove the vial from the refrigerator and equilibrate with Fig. 2 Invert the vial 20 times holding it from end to end,
room temperature (15 – 30 °C) for at least 15 minutes using a very quick turning motion of your wrist during
mixing.
before use.
2. Roll each vial between the palms of your hands for 15 4. Analyse the QC material on the instrument according to
seconds (see Fig. 1). the Instructions for Use. The pierceable septum in the vial
3. Holding the vial from end to end between the thumb and cap allows sampler analysis.
forefinger, invert the vial 20 times using a very quick 5. Subsequent analyses during this test period may be
turning motion of your wrist during mixing. Details can be performed by inverting the vial 5 times prior to
seen in a video on the CD-ROM or USB stick instrument analysis.
accompanying each QC lot (see Fig. 2). 6. Return the vial to the refrigerator (2 – 8 °C) for storage

You can also watch a movie about the mixing of the

quality control vials on our webpage:
http://www.sysmex-europe.com/media-center/sysmex-qc-
material-preparation-26847.html

A simple procedure with a great impact

When the result of a QC measurement falls outside its
limits, analysis should be stopped, patient results held, and
the analysis system investigated. As soon as error sources
have been identified and corrections made, the
measurement of control material should be repeated. If the
Fig. 1 Roll the QC vial for 15 seconds between the palms of
your hands.
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results read correctly, then patient samples (those Incorrect mixing and its effects
from the period of the last correct QC measurement Identifying mixing problems is generally difficult as
until the QC error has been discovered and solved), it depends on both the intensity and duration of
along with another quality control specimen, should mixing. However, taking a closer look at the two
be repeated. Do not simply repeat the testing extremes (insufficient vs. overmixing) reveals that
without looking for sources of error and taking numerical results of WBC, RBC and PLT can be
corrective action. distorted due to the use of an incorrect mixing
procedure.
According to the World Health Organisation (WHO),
possible problems to consider include [3]: An overmixed sample is generally more difficult to
identify and occurs more rarely. If the sample is
n Degradation of reagents or kits mixed for too long a time with high speed, slightly
n Control material degradation elevated WBC counts together with markedly
n Operator error increased PLT counts can be observed. Never mix
n Failure to follow manufacturer’s instructions the haematology QC vials on an automated roller or
n An outdated procedure manual mixing device!
n Equipment failure
n Calibration error In contrast to that, samples that are not mixed
sufficiently can be identified by markedly increased
In haematology it can be generally observed that a RBC counts and related parameters (HGB, HCT) and
lot of problematic QC results derive from incorrect decreased WBC counts and low counts of PLT-I
handling or inappropriate storage of the material. especially in Level 1 with increased coefficient of
Also using outdated materials or vials with too little variation (CV) values. Table 3 compares the results
remaining volume leads to erroneous results. of improperly mixed QC samples.
Particular in haematology, controls deserve accurate
treatment before measurement as they contain Table 3: Results of improperly mixed QC samples
blood cells that need to be homogenized before
Not mixed Overmixed
measurement.
WBC  WBC ()
Below, some examples are shown where the results
RBC, HGB, HCT  RBC, HGB, HCT not
have been out of their range due to mistreatment of markedly influenced
the QC material. Changes in the numerical results,
PLT-I  PLT-I 
particularly of the complete blood count (CBC) and
reticulocyte parameters, can be observed. Checking Aspirated from the Red blood cells are
the cell distributions in histograms and scattergrams sediment, more red blood destroyed and fall by size
cells are measured, but into the PLT area, where
can also help to reveal differences to results white cells are they are then counted as
underrepresented or latelets.
obtained from correctly treated material. missing
Measurement examples and scattergram images of
all control levels can be found on the CD-ROM or
USB stick that always accompanies the QC material
for comparison purposes.
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Fig. 3 Experiment results using XN Check Level with two different mixing procedures

Applying an incorrect mixing procedure leads to The effect of incorrect temperatures on quality
increased CV values for most parameters as shown control material
in Fig. 3 and Table 4. This was done as an experiment Not only mixing but also temperature has an
to demonstrate the influence of the mixing influence on the results obtained from quality
procedure on platelet results. Two different mixing control materials. Haematology controls must be
procedures were used. For the measurements of stored refrigerated, but may only be used after
phase 1 and 3 (O) the correct mixing procedure was equilibration with room temperature for at least 15
applied, whereas in phase 2 (O) the QC material was minutes. Storing QC materials below 2°C, even
less intensively mixed than described in the package short-term, has an immediate impact on the cells
insert. Platelet results were more imprecise and and results in haemolysis, as shown in Table 5.
significantly lower than the assay mean value.

Table 4 Quantitative analysis of the experiment’s results

Phase 1 Phase 1 Phase 3

(correct (insufficient (correct
mixing) mixing) mixing)

Assay mean for

87 87 87
platelets

Mean 87.0 80.2 86.3

Deviation (%)
0.0 -7.8 -0.8
from assay mean

Standard
2.8 4.7 2.4
deviation (SD)

Deviation (%)
from assay 3.3 5.9 2.8
meACV (%)
Fig. 4 Comparison of a non-haemolysed QC
sample (left) with a haemolysed QC sample (right)
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Table 5 Results of QC samples stored at incorrect temperatures

Conclusion of corrective actions. A poor approach can lead to the

Small things can have a great impact. So has the mixing validation of incorrect patient results, potentially setting off
procedure of QC materials in haematology! As could be seen a spectrum of undesirable scenarios and legal actions in the
above, it greatly influences the QC measurement results. worst case scenario.
Damages that occur to the vial neither reflect a defect of
the analyser nor the necessity for calibration. Therefore, it is References
of utmost importance to store and treat the quality control 1. Phang R et al. (2009): A Practical Guide to Internal
materials in the way the manufacturer describes. Quality Control (IQC) for Quantitative Tests in Medical
Laboratories. Proposed Guidelines.
Take home message 2. CLSI C24 – A3 (2006): Statistical Quality Control for
The main objective of a laboratory is to provide reliable,
Quantitative Measurements: Principles and definitions –
timely and accurate test results to the requesting
persons. To continuously achieve this day in, day out, Approved Guideline.
you need consistent monitoring and evaluation of the 3. WHO Content Sheet 7 – 1: Overview of Quality Control
laboratory’s performance, and in case of non-conformance for Quantitative Tests. http://www.who.int/ihr/training/
to the procedures – the implementation and follow-up laboratory_quality/7_b_content_quant_qc.pdf

Sysmex South Africa (Pty) Ltd.

Fernridge Office Park – Block 2, 5 Hunter Avenue, Ferndale, Randburg 2194, South Africa · Phone +27 11 3299480 · Fax +27 11 7899276 · info@sysmex.co.za · www.sysmex.co.za