RX SERIES LATEX ENHANCED IMMUNOTURBIDIMETRIC ASSAY FOR THE MEASUREMENT OF LIPOPROTEIN (A) ON THE RX MONACO ANALYSER
RX SERIES LATEX ENHANCED IMMUNOTURBIDIMETRIC ASSAY FOR THE
MEASUREMENT OF LIPOPROTEIN (A) ON THE RX MONACO ANALYSER
INTRODUCTION
What is Lipoprotein(a)?
Lipoprotein(a), also known as Lp(a) or lipoprotein-
little-a, are particles that are made in the liver
and found in the blood plasma that transport
cholesterol, phospholipids, triglycerides and
apolipoproteins. The amount that is present in
your body is mainly determined by genetics and
varies widely hence, the levels of Lp(a) can vary
up to 1000-fold between individuals. Lipoprotein
is assembled from a cholesterol rich LDL particle
and two protein molecules; including apoliporotein
apo(a) and apolipoprotein B100. Although the size
of apolipoprotein B100 is the same for everyone
the size of apo(a) is genetically determined and
differs between individuals and can vary widely.
Having a high level of Lp(a) (greater than 500mg/L
or 120nmol/) increases your risk of cardiovascular
disease (CVD). Levels of Lp(a) do not change
throughout life and are usually unaffected by lifestyle
or the environment. According to the British Heart
Foundation, an average of 420 people die from CVD
each day which equates to one death every three
minutes.
What is Lp(a) used for?
Although having some cholesterol and Lp(a) in
your blood is normal, elevated concentrations of
Lp(a) are a risk factor for coronary heart disease
(CHD), a heart attack, peripheral vascular disease,
aortic stenosis, blood clots and stroke. Therefore
measuring Lp(a) offers the possibility of early
diagnosis and risk of CVD. It has been estimated
that one in five people globally have a high level of
Lp(a) and remain unaware despite high Lp(a) being
a common condition. Additionally around 30% of
those diagnosed with Familial Hypercholesterolemia
have high levels of Lp(a). If a parent has been
diagnosed with high Lp(a) then their children will
have a one in two chance of inheriting it also. An
Lp(a) test is recommended for families where heart
attacks and stroke are common, especially at a
young age and where no additional risk factors are
known to be a contributing factor.
Yet despite the above evidence and the
recommendation of screening for elevated Lp(a)
from the European Atherosclerosis Society,
measurement of Lp(a) is not conducted in clinical
practice. This is largely due to the major challenge
associated with Lp(a) measurement and the size
variation of apo(a) with Lp(a). Dependent upon the
size of apo(a) in the assays calibrator, many assays
under or overestimate apo(a) size in the patient
sample which can lead to patient misclassification.
The Randox assay is one of the only methodologies
on the market that detects the non-variable part of
the Lp(a) molecule and therefore suffers minimal
size related bias; providing accurate and consistent
results. The Randox Lp(a) kit is standardised to
the WHO/IFCC reference material SRM 2B and
is closest in terms of agreement to the ELISA
reference method.
Clinical significance of Lp(a)
Lp(a) determination is intended for use in
conjunction with clinical evaluation, patient risk
assessment and other lipid tests to evaluate
disorders of lipid metabolism and to assess
coronary heart disease risk in specific populations.
Evidence suggests that between 60-70% of African
populations are estimated to have between 250-
300mg/L levels of Lp(a) putting them at greater
risk of developing CVD compared to Chinese
and Japanese populations; where only 30% of the
population is estimated to have between 250-
300mg/L levels of Lp(a).
Scientific Study
This study reports the development of an
immunoturbidimetric assay kit with enhanced
precision and accuracy for the measurement of
Lp(a) in human serum and plasma applied to the
fully automated bench top/floor standing analyser
RX monaco. The assay is applied to the fully
automated RX series analysers and is also suitable
for use on many mainstream clinical chemistry
platforms. This is of value as an accurate, stable
and convenient tool for the determination of
Lipoprotein(a) using these automated systems.
Methodology
Agglutination occurs due to an antigen-antibody
reaction between Lp(a) in a sample and anti-
Lp(a) antibody adsorbed to latex particles. This
is detected as an absorbance change at 700 nm
proportional to the concentration of Lp(a) in the
sample. Concentrations are calculated from a multi-
point calibration. On-board and calibration stabilities
were tested by storing the reagents uncapped
on the analyser for a period of 28 days. Within-
run and total precision were assessed by testing
serum samples at defined medical decision levels,
4 replicates twice a day for 20 days. Correlation
studies were conducted using another commercially
available clinical chemistry system.
Prozone was not observed up to 493 mg/dL
RESULTS
Sensitivity and linearity
12/196/LPA
Reagent on-board stability
12/001/LPA
Assay Sensitivity Assay Linearity
Lp(a) 6.18 mg/dL 103 mg/dL
Specimen Type nMean Within-Run Precision Total Precision
mg/dL SD %CV SD %CV
QC Level 1 80 17.71 0.49 2.8 0.66 3.7
Patient sample 80 24.00 0.98 4.1 1.43 5.9
Serum pool 80 29.25 0.6 2.0 0.71 2.4
Calibrator L5 80 72.29 1.27 1.8 2.65 3.7
Specimen Type: Within-Run Precision and Total Precision
Analyte 16 mg/dL 40 mg/dL
Haemoglobin 1000 mg/dL 1000 mg/dL
Free Bilirubin 60 mg/dL 60 mg/dL
Conjugate Bilirubin 60 mg/dL 60 mg/dL
Triglycerides 2000 mg/dL 2000 mg/dL
Intralipid® 2000 mg/dL 2000 mg/dL
Correlation
This method (Y) was compared with another
commercially available method (X) and the following
linear regression equation obtained:
Y = 0.97X + 0.59
and a correlation coefficient of r = 1.00
40 patient samples were analysed spanning the range
6.51 mg/dL to 101.97 mg/dL.
The Randox Lp (a) test kit shows minimum apo
(a) size related bias. Size heterogeneity of apo(a)
can affect to varying degrees the outcome of other
commercially available kits.
Interference
The analytes below were tested up to the following
levels and were found not to interfere at Lp(a)
concentrations of 16 mg/dL and 40 mg/dL.
Analyte Interference Levels at 16mg/dL and 40mg/dL
Correlation Lp(a) assay on RX monaco vs
available clinical chemistry system
FINDINGS The Randox Lp(a) immunoturbidimetric
assay applied to the bench top/floor standing
RX monaco analyser, exhibits high sensitivity and
reproducibility with the added advantage of using
reagents with good stability. This is of value in the
accurate determination of this analyte in human
serum/plasma for clinical and research applications.
The Randox Lp(a) immunoturbidimetric assay is
also available on all fully automated RX analysers
including the RX imola, RX daytona+ and
RX modena.
Further information on the assay and RX analyser
used within this study
Lp(a) features:
• Sample type - Suitable for use with serum
and plasma
• Immunoturbidimetric method - Making it simple
and quick to perform
• Liquid ready-to-use reagents - For ease of use
and convenience
• Excellent stability - All reagents are stable to
expiry date when stored at +2-8ºC or 28 days
on board the analyser at approximately 10°C.
• Extensive measuring range 3-90 mg/dl -
Ensuring concerning levels of Lipoprotein(a) are
comfortably detected
• Superior 5-point calibrator available - Providing
a complete diagnostic testing package
Advantages of the RX analysers for testing:
• Low water consumption
• User friendly software
• High throughput of tests including ISE
(analyser dependent)
• Low sample volume required
• STAT sample functionality
• Dual 5 speed stirrers optimized for each
chemistry reaction
• Reagent micropipette with liquid level sensor
and crash detection
• Liquid level sensor, crash, bubble and clot
detection
Randox Laboratories Ltd, 55 Diamond Road, Crumlin, County Antrim, BT29 4QY, United Kingdom +44 (0) 28 9442 2413 • [email protected] • randox.com/clinical-chemistry-analysers/
Information correct at time of print. Randox Laboratories Ltd is a subsidiary of Randox Holdings Limited a company registered within Northern Ireland with company number N.I. 614690. VAT Registered Number: GB 151 6827 08. Product availability may vary from country to country. Please contact your local Randox representative for information.
Products may be for Research Use Only and not for use in diagnostic procedures in the USA.
REFERENCES
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6. Marcovina, S.M., Albers, J.J., Scanu, A.M. et al. (2000) Use of a Reference Material Proposed by the
International Federation of Clinical Chemistry and Laboratory Medicine to Evaluate Analytical Methods for
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7. Lipoprotein a Foundation. 2018. Understand Inherited Lipoprotein(a). [ONLINE] Available at: http://www.
lipoproteinafoundation.org/?page=UnderstandLpa. [Accessed 10 May 2018].
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9. Lipoprotein (a). (2014). 1st ed. [ebook] England: Heart UK - The Cholesterol Charity. Available at: https://
heartuk.org.uk/files/uploads/huk_fs_mfss_lipoprotein_02.pdf [Accessed 10 May 2018].
NOTES:
Information correct at time of print. Randox Laboratories Ltd is a subsidiary of Randox Holdings Limited a company registered within Northern Ireland with company number N.I. 614690. VAT Registered Number: GB 151 6827 08. Product availability may vary from country to country. Please contact your local Randox representative for information. Products may be for Research Use Only and not for use in diagnostic procedures in the USA.