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• It is best to use a 19–21 G needle for blood draw (for children it can be 22-23 G)

• Avoid pumping

• Apply a tourniquet for 30 seconds (no more than 1 minute)

• Puncture vessel, loosen tourniquet, collect blood

• Discard the first (neutral) tube if the puncture is problematic

• Collect 3 to 4 ml of whole blood in a neutral tube/ syringe and use for other analyses

• Take the next tube for platelet function testing before different tubes with other coagulants

• Use follow-up collection tubes for platelet analysis – avoid foaming and drawing off too quickly (slow aspiration of the blood)

• Fill the tubes as recommended by the manufacturer and mix gently (move 4 times in an infinity sign)

• Record the time of blood collection on the sample

References:

1. Greiner J et al. Diagnosis of platelet dysfunction – thrombocytopathies: Interdisciplinary S2k guideline of the Standing Committee on Paediatrics of the German Society for Thrombosis and Haemostasis Research (GTH). AWMF Guidelines.

2. Kitchen S et al. International Council for Standardisation in Haematology (ICSH) recommendations for collection of blood samples for coagulation testing. Int J Lab Hematol. 2013;35(1):1–13.

For platelet function tests with IMPACT, it is recommended that tests be performed between 30 minutes and 3 hours after blood collection.

Blood collection stresses platelets, pre-activating them; they should rest for 30 minutes so that all (non-inhibited) platelets can be activated by the reagents.

Transport at room temperature, avoiding shaking.

Reference:

1. Greiner J et al. Diagnosis of platelet dysfunction – thrombocytopathies: Interdisciplinary S2k guideline of the Standing Committee on Paediatrics of the German Society for Thrombosis and Haemostasis Research (GTH). AWMF Guidelines.

Store blood sample tubes for platelet function testing at room temperature, never on the roller mixer or other mechanical mixer.

Mix gently directly before pipetting.

References:

1. Greiner J et al. Diagnosis of platelet dysfunction – thrombocytopathies: Interdisciplinary S2k guideline of the Standing Committee on Paediatrics of the German Society for Thrombosis and Haemostasis Research (GTH). AWMF Guidelines.

2. Chiesi Farmaceutici S.p.A. Kengreal: Instructions for Use (IFU). Parma: Chiesi Farmaceutici S.p.A.

Anticoagulants represent a significant variable in platelet function testing. Different anticoagulants prevent blood clotting by different mechanisms, each creating a unique non-physiologic setting that can modify platelet function. The following anticoagulants are recommended for use with IMPACT:

Hirudin prevents blood coagulation by directly inhibiting thrombin. Physiological levels of calcium are preserved, resulting in increased stability of platelet function.

Sodium citrate (Na-citrate), the traditional anticoagulant of choice, prevents blood coagulation by chelating calcium and may interfere with platelet responses to specific agonists due to the depletion of calcium ions essential for platelet activation.

References:

1. Peerschke EI et al. Reference range determination for whole-blood platelet aggregation. Am J Clin Pathol. 2014;142(5):647–56.

2. Kroll MH, Schafer AI. Biochemical mechanisms of platelet activation. Blood. 1989;74(4):1181–95.

3.2 % citrate sample tube: Yes. Precise filling of the blood tube is of particular importance for citrate tubes. Citrate binds the free calcium in the blood, which is necessary for platelet aggregation. The calcium is added from the dilution solution with a certain amount of CaCl₂, based on a correctly filled tube.

Hirudin sample tube (Sarstedt, order number 04.1959.001) : For hirudin, the influence of underfilling is not so problematic as for citrate, but it is not recommended. A reduction in end blood volume of up to 50%, e.g. in emergency case, (Hirudin concentration > 525 ATE/ml) should not significantly influence the results (confirmed by experience).

References:

1. Sarstedt AG & Co. Basics of venous blood collection. [Internet]. Nümbrecht: Sarstedt; [cited 2025 Jun 20]. Available from: https://www.sarstedt.com.

2. Peerschke EI et al. Reference range determination for whole-blood platelet aggregation. Am J Clin Pathol. 2014;142(5):647–56.

Platelets are more active in Hirudin than in citrated blood which makes it the preferred anticoagulant for looking at aggregation reactivity.  This does lead to some clumping in vitro which can be visualised in counting chambers, but Hirudin blood is very well suited to IMPACT whole blood impedance aggregometry.

Reference:

1. Greiner J et al. Diagnosis of platelet dysfunction – thrombocytopathies: Interdisciplinary S2k guideline of the Standing Committee on Paediatrics of the German Society for Thrombosis and Haemostasis Research (GTH). AWMF Guidelines.

No, Both venous and arterial blood can be used for IMPACT whole blood impedance aggregometry.

Reference:

1. Kafian H et al. Comparison of venous and arterial blood sampling for the assessment of platelet aggregation with whole blood impedance aggregometry. Scand J Clin Lab Invest. 2011;71(8):637–40.

Generally, blood samples for platelet function should not be sent by PTS. Platelets may be activated, and foam may form, rendering the sample unusable.

However, some hospitals have PT systems that handle blood samples very slowly and gently. In this case, their use should be validated with comparative measurements before use.

References:

1. Greiner J et al. Diagnosis of platelet dysfunction – thrombocytopathies: Interdisciplinary S2k guideline of the Standing Committee on Paediatrics of the German Society for Thrombosis and Haemostasis Research (GTH). AWMF Guidelines.

2. Bolliger D et al. Pre-analytical effects of pneumatic tube transport on impedance platelet aggregometry. Platelets. 2009;20(7):458–65.

3. Enko D et al. Pneumatic tube system transport does not alter platelet function in optical and whole blood aggregometry, prothrombin time, activated partial thromboplastin time, platelet count and fibrinogen in patients on anti-platelet drug therapy. Clin Chem Lab Med. 2016;54(4):e101–3.

Before the measurement is started, an electronic self-check is done every time (many systems perform an electronic quality control once in 24 h).

A liquid control checks pipette functionality, device temperature, operator competency and the electronics in low and high results.

Performance of a normal sample vs. a routine panel of agonists is encouraged as well as the addition of inhibitors (IMPACT ASA, IMPACT P₂Y₁₂ and IMPACT GPIIbIIIa) as positive controls.

This information and a full list of our reagents can be found here.

Yes, IMPACT is supported by a range of lyophilised reagents; IMPACT ASA (with IMPACT ARA) and IMPACT P₂Y₁₂ (with IMPACT ADP). In addition, a liquid GPIIbIIIa antagonist (with IMPACT TRAP) is available.

Appropriate pipette programs to support these reagents are available in the software.

The result is quantitative. If the platelet count is below 100,000, then aggregation can gradually diminish (qualitative result).

The TRAP-6, as the strongest activator of platelets, will normally show some aggregation down to quite low levels (40,000),  when it shows no aggregation the primary haemostasis potential is typically very low.

It should always be noted that the platelet function is not proportional to the platelet count.

Reference:

1. Hanke AA et al. Impact of platelet count on results obtained from multiple electrode platelet aggregometry (Multiplate®). Eur J Med Res. 2010;15(5):214–9.

It depends on the dosage and speed of metabolism:

Acetylsalicylic acid: intravenous (IV) application acts immediately. Orally, 500mg and 100 mg doses act reliably within 15 minutes (package insert Aspirin®, Bayer AG)

Clopidogrel: 2 – 6 hours after loading dose, dependent on the dosage (800 mg 2 hours, 300 mg min. 6 hours)

Prasugrel and ticagrelor: In general, acts after 30 minutes; it could be delayed if intestinal absorption is delayed (e.g. by other medications).

Cangrelor: Intravenous administration acts after 2 minutes.

References:

1. Bayer AG. Aspirin: Instructions for Use (IFU). Leverkusen: Bayer GmbH.

2. Sanofi, Bristol-Myers Squibb. Plavix: Instructions for Use (IFU). Sanofi & BMS.

3. Eli Lilly and Company. Effient: Instructions for Use (IFU). Indianapolis: Eli Lilly.

4. AstraZeneca. Brilinta: Instructions for Use (IFU). Cambridge: AstraZeneca.

5. Chiesi Farmaceutici S.p.A. Kengreal: Instructions for Use (IFU). Parma: Chiesi Farmaceutici S.p.A.