Aspirin Reactivity Units
Label Mnemonic: ARU
Epic Lab Code: LAB8084
Downtime Form: A-1a General Laboratory Requisition
Hematology
6240 RCP
356-3527
Specimen(s):
Whole Blood
Specimen Instructions:
Must be drawn in special sodium citrate tubes. Call Tech Services (356-3527) for collection kit.
Collection Medium:
Special Coagulation Tube
Minimum:
Must be collected in a (2 mL) special collection tube.
Rejection Criteria:
If specimen is over 4 hours old and not drawn in special collection tubes. Improper sample collection (platelet activation) or patient's exposure to other anti-platelet agents.
Delivery Instructions:
Must be hand-delivered to laboratory within 2 hours of collection; specimen cannot be sent using pneumatic tube system. Keep at room temperature.
Testing Schedule:
24 hrs/day, 7 days a week, including holidays.
Turn Around Time:
1 hour (upon receipt in laboratory)
Reference Range:
620-672 ARU (pre-drug administration) Therapeutic range: <550 ARU
Interpretive Data:
<550 ARU.
Platelet dysfunction consistent with aspirin has been detected.

Patients who have been treated with Glycoprotein IIb/IIIa inhibitors should not be tested until platelet function has recovered. This time period is approximately 14 days after discontinuation of abciximab (ReoPro) and up to 48 hours after discontinuation of eptifibatide (Integrilin) and tirofiban (Aggrastat).
Test Limitations:
Improper sample collection (platelet activation) or patient's exposure to other anti-platelet agents.
Methodology:
The VerifyNow system incorporates the agonist arachidonic acid to activate platelets.
CPT Code:
85576