Document # 49044IM1
Revision 7.5 16
Dated February 16, 2017
INTERPRETATION:
Aggregation curves in PRP can be interpreted as follows:
• By direct comparison to a normal drug free control which
also provides real time quality control.
• Comparison to published normal values that can be verified
and reproduced by any laboratory.
With Collagen: Collagen is useful for checking the platelet’s
general ability to aggregate. A lag phase of up to a minute is
typically seen with this agonist.
With Arachidonic Acid: Arachidonic Acid is converted to
thromboxane A
2
in the presence of cyclooxygenase. Aspirin
inhibits the cyclooxygenase pathway, causing a significant
reduction in aggregation with this agonist. Normal aggregation is
seen with concentrations of 0.5 mM to 1.0 mM.
With ADP: ADP exposes the fibrinogen binding site on the
membrane glycoprotein GPIIb/IIIa complex. Aggregation testing is
typically performed in PRP with concentrations ranging from 1 µM
to 10 µM. At the lower concentrations up to 3 µM, a first wave of
aggregation will be followed by disaggregation. At the higher
concentrations, the first wave of aggregation will blend into the
second wave, masking the biphasic wave. It is often necessary to
perform dose-response testing with multiple concentrations to
obtain a biphasic response. Aspirin effect may be seen with mid-
range concentrations such as 5 µM.
2
With Epinephrine: Shape change is not seen with this agonist.
Higher concentrations (≥ 5 µM) produce a biphasic curve with
second-wave aggregation dependent on thromboxane A
2
synthesis. “Epinephrine is the least consistent agonist used in the
assessment of platelet aggregation and, if the Epinephrine
response is the only abnormality seen in testing, one should be
very hesitant to make the diagnosis of a ‘disorder’ based on this
result.”
18
With Ristocetin: This antibiotic is used for the detection of von
Willebrand Disease (a quantitative or qualitative defect in plasma
vW Factor) and Bernard Soulier (a lack of platelet membrane
glycoprotein (GPIb). Normal results are seen with concentrations
ranging from 0.75 to 1.5 mg/mL. To detect Type 2B or Platelet-
Type vW, test for a Hyper-response at low concentrations (0.2 –
0.6 mg/mL).
7
To distinguish between vW and Bernard Soulier,
add normal plasma or cryoprecipitate to patient sample. vW
patient will respond, Bernard Soulier will not. A Qualitative defect
such as a saw-tooth pattern may be seen with subjects taking
aspirin.
PROCEDURE NOTES:
1. With the Model 490 4+4, spacers are not required when
testing micro-volume samples (250 µL of PRP) and all
CHRONO-PAR® reagent volumes are reduced by half. For
example: 5 µ
µµ
µL of ADP = a final concentration of 10 µ
µµ
µM with
a 500 µ
µµ
µL PRP sample… use only 2.5 µ
µµ
µL with a 250 µ
µµ
µL PRP
sample.
2. It is important that the pipette tip be pushed to the bottom
of the cuvette & the reagent forcefully injected into the
sample. DO NOT introduce the reagent above the sample in
the cuvette since the reagent will cling to the side of the
cuvette and will not mix with the sample. (DO NOT forcefully
inject reagent if testing with smaller volume of 250 µL PRP.)
LIMITATIONS OF THE PROCEDURE:
• In a study of one hundred and six patients with storage pool
deficiency (SPD), 23% had normal optical (PRP) aggregation
responses to ADP, Epinephrine and Collagen; and 44% had
miscellaneous aggregation abnormalities. The authors
concluded that SPD is common, heterogeneous and not
necessarily associated with optical (PRP) aggregation
abnormalities.
10
• Tests should be performed within 3 hours of venipuncture.
• Many drugs inhibit platelet function.
5,11,19
Unless the aim of
testing is to demonstrate drug-induced inhibition, patients
should be drug free for ten (10) days to two (2) weeks prior
to testing.
• Further Clinical and Laboratory evaluation may be required
to confirm diagnosis.
• Red Blood Cells in PRP can inhibit the ability of the
Aggregometer to detect changes in light intensity. This may
cause the appearance of a decrease in platelet
aggregation.
19
• Hemolysis results in release of nucleotides from the red cells
which may cause activation or desensitization of platelets,
especially to ADP
.19
• Lipids in PRP can interfere with light transmission readings &
prevent recording of aggregation.
• Platelet counts below 100,000/µL may cause problems with
the setting of optical baseline, preventing the recording of
aggregation
• This device has not been evaluated for pediatric use.
SERVICE/PREVENTATIVE MAINTENANCE
This Unit does not require Preventative Maintenance; however,
yearly calibration is recommended. Calibration and service, if
required, should be obtained from the factory or a factory
authorized representative.
In the 48 continental United States a Factory Service and Loaner
Contract program is available. On-site field service is also
available in some areas. Contact the factory for details.
Outside of the United States contact your distributor for service.
In countries where there is no distributor, contact Chrono-log
directly.
Replacement of Parts: Critical components should only be
replaced with manufacturer approved parts. Maintenance should
be performed according to service manuals and PM checklists.
Protective Earth Ground: The instrument is connected to ground
at the instrument chassis. This sole purpose connection point is
made between the power entry module and the chassis with
green/yellow wire and is marked with the IEC 60417-5019
symbol. This connection must be reestablished if it is
removed for any purpose during servicing.
CLEANING SYSTEM COMPONENTS
Recommended Tools and Accessories
A Liquid Dishwashing Detergent -- Use a mixture of one part liquid
dishwashing detergent and three parts water to clean the exterior
of the Aggregometer.
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