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Hart Biologicals Ltd, 2 Rivergreen Business Centre, Queens Meadow, Hartlepool TS25 2DL. UK Tel: +44 (0) 1429-271100 Fax: +44 (0) 1429-277085 www.hartbio.com, e-mail: info@hartbio.com

INTENDED PURPOSE

Hart Biologicals GpIIb/IIIa Antagonist Reagent is used as a positive control in platelet aggregation studies using human platelet rich plasma or whole blood.

SUMMARY

The GpIIb/IIIa Antagonist Reagent contains a synthetic inhibitor of the platelet Glyocoprotein IIb/IIIa Receptor on human platelets ¹,² .This receptor is responsible for fibrinogen binding to platelets, allowing cross linking between platelets during platelet aggregation. The Hart Biologicals GpIIb/IIIa Antagonist Reagent can be added to platelet aggregation test to confirm that platelet function can be inhibited in situations where patient results are not as expected.

TEST PRINCIPLE

The platelet aggregation test measures the rate and degree to which dispersed platelets in a sample of platelet rich plasma (PRP) or anticoagulated whole blood forms clumps (aggregates) after the addition of a substance that normally stimulates platelet aggregation (agonist). In optical aggregometry, the clumping of the platelets causes the platelet rich plasma to become less turbid . This is measured on a platelet aggregometer, which plots the rate and maximum extent of the aggregation reaction. In whole blood aggregometry, platelets adhere to small wires suspended in the blood sample and the impedance between the wires as the platelets adhere and aggregate is measured and plotted. The addition of Hart Biologicals GpIIb/IIIa Antagonist Reagent to the test platelets prior to activation with reagents such as ADP, Collagen, TRAP-6 or Arachidonic Acid will result in significantly inhibited or even zero platelet aggregation. If a normal level of aggregation is recorded in the presence of GpIIb/IIIa Antagonist Reagent, then other non-specific reasons for platelet aggregation should be considered.

WARNINGS AND PRECAUTIONS

For in-vitro diagnostic use only. Do not pipette by mouth. Do not smoke, eat or drink in areas where specimens or kit reagents are handled. Wear disposable gloves when handling specimens and kit reagents, and wash hands thoroughly afterwards.

MATERIALS PROVIDED

GpIIb/IIIa Antagonist Reagent

Ingredients: The reagent contains liquid preparation of 50µg/ml (101µM) GpIIb/IIIa Antagonist with added buffer and stabilisers.

Preparation for use: The GpIIb/IIIa Antagonist Reagent is ready for use as packaged.

Storage and stability: Unopened vials of GpIIb/IIIa Antagonist Reagent should be stored at 2-8°C. The Reagent is stable until the expiry date printed on the vial label. Opened vials of Reagent are stable for 30 days when stored at 2-8°C

MATERIALS REQUIRED BUT NOT PROVIDED

Platelet aggregometry system – the Hart Biologicals GpIIb/IIIa Antagonist Reagent will perform satisfactorily when used on any aggregometer system. Follow the manufacturer’s instructions for the operation of the aggregometer in use.

SAMPLE COLLECTION AND PREPARATION³

Preparation of Platelet-Rich and Platelet- Poor Plasma for Optical Aggregation

Blood for platelet aggregation testing should be collected in to plastic syringes and transferred to plastic tubes, or collected in siliconised glass evacuated blood collection tubes.

Blood (9 parts) should be mixed with 0.11M or 0.13M sodium citrate anticoagulant (1 part). Invert gently to mix. Do not shake.

• Prepare platelet rich plasma by centrifuging the anti-coagulated blood at 150-200 x g for 10-15 minutes at room temperature.
• Remove the platelet rich plasma with a plastic transfer pipette and place in a plastic container (with cap) labelled ‘PRP’. Cap the container and keep at room temperature.
• Prepare platelet poor plasma by centrifuging the remaining blood specimen at 2000 x g for 20 minutes.
• Remove the platelet poor plasma with a plastic transfer pipette and place in a plastic container (with cap) labelled ‘PPP’. Cap the container and keep at room temperature.
• Adjust the platelet concentration in the PRP to 200-300x10⁹/L using PPP, cap and allow to stand at room temperature for 30 minutes prior to testing.
• Testing should be completed within 3 hours of blood collection.

Whole Blood Aggregation Samples

Refer to the aggregometer manufacturer recommendations for the preparation of samples for whole blood aggregometry.

TEST PROCEDURE

A) Optical Aggregometry

1. Set the 0% and 100% aggregation levels on the aggregometer using platelet poor plasma and platelet rich plasma according to the manufacturer’s instructions.
2. Pipette the required volume of platelet rich plasma in to an aggregation cuvette and add a stir bar.
3. Add the required volume or concentration of GpIIb/IIIa Antagonist Reagent to the cuvette. Typically this will be 10% of the final test volume.
4. Pre-warm to 37°C for 120 seconds.
5. Add the required volume of platelet aggregation reagent (e.g. ADP, Collagen, Arachidonic Acid or TRAP-6) directly in to the cuvette. Do not allow reagent to run down the wall of the cuvette.
6. Allow the aggregation pattern to form for a minimum of 5 minutes.

B) Whole Blood Aggregometry

Refer to the manufacturer’s instructions for the correct performance of the test.

QUALITY CONTROL

The results of platelet aggregation studies should be interpreted against the results of aggregation profiles of a normal sample tested at the same time. The normal donor should not have ingested aspirin or aspirin containing compounds in the preceding 10 days and should not be on any other form of anti-platelet medication.

EXPECTED VALUES

The inclusion of GpIIb/IIIa Antagonist Reagent should lead to significantly reduced or abolished aggregation response for stimulated platelets.

FURTHER TESTING

If the test results are abnormal, the test should be repeated on a separate occasion. If the results are consistently abnormal, and the patient is not taking any medication known to interfere with platelet function, additional tests should be considered.

LIMITATIONS

In optical aggregometry, the presence of red blood cells in the PRP will cause the total observed aggregation to be reduced. The presence of platelets in the PPP will cause the total observed aggregation to appear increased. Spurious results can be observed when the total platelet count of the PRP is less than 75 x 10⁹/L. PRP tested less than 30 minutes after preparation may exhibit abnormal aggregation profiles.

Bibliography

1. Peerlinck, De Lepeleire, I., Goldberg, M et al. ‘A Selective Nonpeptide Platelet Glycoprotein IIb/IIIa Antagonist, Is Active In Man’, Circulation, 1993; 88: 1512-1517
2. Kumar, A. and Herrmann, H.C. ‘Tirofiban: An Investigational Platelet Glycoprotein IIb/IIIa Receptor Antagonist’. Exp. Opin. Invest. Drugs. 1997; 6: 1257-1267
3. Dacie & Lewis, ‘Practical Haematology’, Lewis, S.M., Bain, B.J. and Bates, I. (Editors); 9ᵗʰ Edition, Elsevier Science Ltd., 2002, pages 383-385.