Test Overview
Test Methodology

Automated platelet induced aggregation.

Test Usage

Aid in the detection of platelet inhibition due to aspirin therapy.

Reference Range *

Test results are reported in Aspirin Reaction Units (ARU). Therapeutic range for effective platelet inhibition for patients on an aspirin regimen is 350-549 ARU. Values of 550-700 ARU are seen in patients not on aspirin therapy or where therapy is not effectively inhibiting platelet function.

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations
  • Glycoprotein IIb/IIIa inhibitors (tirofiban/Aggrastat®, eptifibatide/Integrilin®, abciximab/ReoPro®), dipyridamole, clopidogrel, or non-steroidal anti-inflammatory drugs (NSAIDS) that inhibit COX-1 and/or COX-1, COX-2 enzymes (ibuprofen, naproxen, diclofenac, indomethacin, and piroxicam) have been documented to inhibit platelet function.
  • NSAIDS taken within the last 24 hours may result in decreased ARU values; however, if an NSAID is ingested at the same time as aspirin, this may result in a higher ARU than with aspirin alone.
    Platelet counts less than 92K , and Hematocrit values less than 29% or greater than 56% can interfere with testing and valid results may not be obtained.
    The Aspirin Platelet Function assay is not intended for use with inherited platelet disorders such as von Willebrand Factor Deficiency, Glanzmann Thrombasthenia and Bernard-Soulier Syndrome.
Test Details
Days Set Up
Daily, 24 hours
Analytic Time

1 hour

Soft Order Code
MiChart Code
Aspirin Platelet Function Test
  • Aspirin Platelet Function Test
  • Verify Now Aspirin
  • Aspirin Response
  • Aspirin Resistance
Specimen Requirements
Collection Instructions

Collect specimen in a 2.7 mL blue top (citrate 3.2%) tube using a 21 gauge or larger needle. Mix by inversion. Do not centrifuge. Whole blood specimen should arrive at lab within 3 hours of collection; transport at room temperature. Collection of the blood through lines that have been previously flushed with heparin should be avoided. If the blood must be drawn through a VAD (vascular access device), the line should be flushed with 5 mL of saline and the first 5 mL of blood or six dead space volumes of the VAD discarded.

Special Handling


Patients who have been administered glycoprotein IIb/IIIa inhibitors tirofiban (Aggrastat) or eptifibatide (Integrilin) within the last 2 days or abciximab (ReoPro) within the last 2 weeks should not be tested.
Normal Volume
Full 2.7mL tube preferred, full 1.8mL tube is acceptable
Minimum Volume
Full 2.7mL tube preferred, full 1.8mL tube is acceptable
Rejection Criteria
Specimens will be rejected if not properly filled, clotted, grossly hemolyzed, or contaminated with heparin, or sent through the pneumatic tube system.
Additional Information

Surgical Screen: Patients administered anti-platelet therapies are at risk of increased bleeding during operations. It is recommended that patients on aspirin undergoing surgery or invasive procedures be tested preoperatively . Test results may aid in decisions to initiate or delay surgery, and to make preparations for additional blood product use if surgery cannot be postponed. Therapeutic Response: Variability in patient response to anti-platelet drugs is common. It is recommended that patients on aspirin be tested to determine if the drug has produced the expected antiplatelet effect. Aspirin studies show that up to a quarter of patients are not responding to its antiplatelet effects, and those patients are 2-3 times more likely to have a major heart attack or stroke.

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Fee Code