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Test Code ARU Aspirin Reactivity Unit (ARU)

Important Note

Contact performing laboratory to obtain proper collection tubes (Greiner Brand).

SPECIAL INSTRUCTIONS: A waste tube must be collected before Greiner tubes are collected.  The collection needle must be 21 gauge or larger. 

Specimens cannot be transported through the pneumatic tube system or in a vehicle.

Performing Laboratory

General Hospital Laboratory          304-388-6244

Specimen Requirements

Whole Blood- Greiner Brand Sodium Citrate Tubes

Draw 2 full, tubes by “clean” venipuncture (no excessive trauma).

Immediately after draw, invert tubes several times to mix blood with additive.

Specimen Rejection

  • Improperly labeled, collected, stored, and transported
  • Quantity not sufficient
  • Specimen clotted
  • Specimen sent through pnuematic tube system
  • Specimen centrifuged

Storage and Stability

Stable at room temperature for 4 hours

Reference Values

> 550 ARU:  Platelet dysfunction consistent with aspirin has not been detected.

 

<550 ARU:  Platelet dysfunction consistent with aspirin has been detected.

Methodology

Light Transmission Aggregometry

Days Test Set Up and Turnaround

Monday through Sunday, Continuously

AM Collection Expected by 9AM same day
Routine Expected within 24 hrs
Stat Expected within 1 hr
Timed Expected results are test dependant

CPT Coding

85576

Additional Information

P2Y12 Inhibitors:  Plavix®, Ticlid ®, and Effient® are commonly prescribed in conjunction with aspirin.  While infrequent, these agents may cause a reduction of ARU in some patients.  However, the effect of the P2Y12 inhibitors did not affect the categorization of patients taking aspirin as having platelet dysfunction (i.e. ARU < 550) due to aspirin ingestion.  The duration of inhibitory effects varies among these P2Y12 inhibitors.  Average durations are listed below:

•   Plavix (up to 5 Days)

•   Ticlid (up to 5 Days)

•   Effient (up to 10 days)

 

Other Anti-Platelet Agents:  These agents can all inhibit platelet function and may result in a decreased    ARU value independent of the effects of aspirin. The duration of inhibitory effects varies among drugs. Average duration times are listed for each drug.

•    Aggrenox (10 days)

•    Persantine (12 hours)

•     Pletal/Cilostazol (12 hours)

 

NSAIDs:  Like aspirin (ASA), NSAIDs have been documented to inhibit platelet function.  Unlike ASA, NSAIDs do not irreversibly inhibit platelet function. This may lead to less platelet inhibition by ASA if the NSAID and ASA are taken at the same time. Average duration times for these inhibitory effects are given for each drug.

•    Ibuprofen (Motrin, Advil) (8 hours)

•    Naproxen (Aleve, Anaprox, Naprelan, Naprosyn) (24 hours)

•    Diclofenac (Voltaren, Cataflam) (24 hours)

•     Indocin (24 hours)

•    Feldene (50 hours)

 

GP IIb/IIIa Inhibitors:  Patients who have been administered tirofiban (Aggrastat®) or eptifibatide (Integrilin®) within two days, or abciximab (ReoPro®) within two weeks should not be tested.

Other classes of commonly used drugs were tested with no significant effect on VerifyNow Aspirin Test performance (antioxidants, ACE inhibitors, antiarrhythmics, anticoagulants, antidepressants, insulin, allopurinol, alcohol, beta blockers, bronchodilators, calcium channel blockers, gastrointestinal medications, betamethasone, lovastatin, and the thyroid hormone L-thyroxine).  The thrombolytic agent streptokinase showed a measurable inhibition of platelet function, as measured by the VerifyNow Aspirin Test.