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Test Code LAB3543 VerifyNow Platelet Inhibition Aspirin Assay

Important Note

Do NOT use tube system to transport samples. Samples must be hand carried to the laboratory. Do not agitate samples. Collect blood sample using largest bore needle possible. Butterfly needles (21 gauge) are ok to use. 

Clinical System Name

VerifyNow Platelet Inhibition Aspirin Assay




Verify Now

Sample Requirements

Specimen: Whole blood

Container(s): 2 Greiner Citrate Tubes -obtain from Core Coag Lab x72561

Preferred Vol: (2) 2 mL tubes - please read instructions in note before drawing.

Minimum Vol: N


Note: Do NOT use tube system to transport samples. Samples must be hand carried to the laboratory. Do not agitate the sample. Testing must be performed within 2 hours of collection. Sample cannot be used for any other testing


Line draws are not recommended for this test.


Preferred method of collection is venipuncture with vacuum fill. Test results are affected by incorrect blood volume. Use largest bore needle possible. Draw blood directly into vacutainer tubes, no syringe draws. Invert sample 4-5 times only.

Use of a Vascular Access Device for the collection of coag testing is not recommended. If this method is used it requires a 5 cc clearing volume; 3 cc for size 2 French catheter or smaller. Blood must be transferred to the Greiner Citrate tubes by use of a blood transfer device to ensure proper fill. 


Lab:   Greiner Citrate tube kits are located in Core Coag Lab x72561

Processing Instructions

Reject due to:

  • Improper tubes.
  • Clotted, Hemolyzed, Insufficient quantity (under fill) or Overfill, and Improper collection.
  • Specimens tubes sent to the lab via the pneumatic tube transport system.
  • Specimen tubes that have been refrigerated, centrifuged, or greater than 2 hours old.

Spin: N

Aliquot: N

Storage location: Core 5 Fridge.


Note: Deliver blood to CORE Coag bench. Coag Technologist will process.


Off-site collection: Cannot be collected outside Seattle Children's Main Campus. Do NOT collect at Seattle Children's Regional Clinic locations. Contact Laboratory for additional information.


Specimen Type Temperature Time

Whole blood

Greiner Citrate Tubes

Room temp ≤2 h
  Refrigerated N
  Frozen N



STAT Performed TAT
N Daily 1 d


Performing Laboratory

Seattle Children's Laboratory



Department: Coagulation

Phone Number: 206 987-2617 (Client Services)

CPT Codes



Method:  VerifyNow System

Analytical Volume: 2 mL Whole blood


Limitations: Results could be affected by the following: GPIIb/IIIa inhibitors, low HCT, low PLT, or inherited platelet disorders. Patients with HCT <20% or PLT <50 K/uL cannot be tested with the VerifyNow Assay.

Samples should be collected between 2 and 30 hours after ingestion of aspirin to show drug effect.

Results could be affected by the following: improper transport, collection via needle smaller than 21 gauge or line draw. Do not use tube system to transport samples. Do not agitate samples, testing must be performed within 2 hours.


Reference Range



≤ 550 ARU




The Aspirin Test is designed to measure platelet function based upon the ability of activated platelets to bind fibrinogen. Fibrinogen-coated microparticles aggregate in whole blood in proportion to the number of unblocked platelet GP llb/llla receptors. Light transmittance increases as activated platelets bind and aggregate fibrinogen-coated beads. The instrument measures this change in optical signal caused by aggregation. Test results are reported as Aspirin Reaction Units (ARU), which are calculated as a function of the rate of aggregation.

Critical Values

Not defined for this test.