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Aspirin Platelet Assay (Aru)
Test CodeAlias/See Also
CPT Codes
85576
Preferred Specimen
Special collection packet required.
Whole blood samples must be collected in or immediately transferred to Greiner 2.0 mL partial fill blue top tubes containing 3.2% Sodium Citrate. The tube must be filled to its intended whole blood capacity (indicated by small black line).
Other Acceptable Specimens
Instructions
Request collection packet by calling 541-2624. Follow order of draw and delivery instructions on outside of packet.
Transport Container
PACKET/4
Transport Temperature
Specimen Stability
Methodology
Optical Signal
Setup Schedule
Daily upon Receipt
Report Available
Limitations
Reference Range
≥ 550 ARU - Platelet dysfunction consistent with aspirin has not been detected.
< 550 ARU - Platelet dysfunction consistent with aspirin has been detected.
The reference range for pre-aspirin samples is 550-700 ARU.
Clinical Significance
Aspirin affects platelets by irreversibly inhibiting the cyclooxygenase-1 (COX-1) enzyme involved in the conversion of arachidonic acid to thromboxane A2, which ultimately activates the GP IIb/IIIa receptors involved in platelet aggregation. If aspirin has produced the expected anti-platelet effect, such aggregation will not occur. The Aspirin Test incorporates the agonist arachidonic acid to activate platelets. The Aspirin Test is designed to measure platelet reactivity based upon the ability of activated platelets to bind fibrinogen. Fibrinogen-coated micro particles aggregate in whole blood in proportion to the number of unactivated platelet GP IIb/IIIa receptors. Light transmittance increases as activated platelets bind and aggregate with fibrinogen-coated beads. The instrument measures this change in optical signal caused by aggregation.