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Platelet Aggregation – Plavix Sensitivity


Plavix (clopidogrel) is a commonly prescribed antiplatelet medication for the prevention of arterial thrombosis. It is a P2Y12 receptor antagonist, inhibiting the activation, degranulation, and aggregation of platelets in response to Adenosine Diphosphate (ADP). A significant subset of patients treated with clopidogrel do not show adequate antiplatelet response due to factors such as variability in drug metabolism, drug interactions, and compliance, leading to increased risk of recurrent cardiovascular events. Plavix sensitivity testing by platelet aggregometry can be used to assess the effectiveness of platelet inhibition by Plavix therapy or restoration of platelet function after discontinuation of Plavix. This test may also be used to measure effectiveness of other ADP receptor (P2Y12) antagonists, such as Effient (prasugrel) or Brilinta (ticagrelor).

STAT: < 24 hours (M-F)

Light Transmittance Aggregometry (LTA)

Draw Tube: Blue Top

Sample Type: Citrated Whole Blood

Specimen Requirements

Sample Type Volume Required Minimum Volume Stability
PREFERRED Citrated Whole Blood Four tubes, 3mL each (or equivalent volume) For pediatric minimum, please call (800) 566-3462. Room Temperature: 4 hours
By appointment only - must arrive at lab within 2 hours of draw
REJECTION CRITERIA Samples received more than 2 hours after draw
SPECIAL INSTRUCTIONS See Draw Guide By appointment only

General Information

METHODOLOGY Light Transmittance Aggregometry (LTA)
STAT TAT < 24 hours (M-F)
STAT TAT Performance > 90% of results released in 24 hours
ROUTINE TAT < 24 hours (M-F)
ALTERNATIVE NAMES Clopidogrel Platelet Function Test, P2Y12 Platelet Function Test, Plavix Test
DESCRIPTION Platelet aggregation is measured in response to ADP and Thrombin Receptor Activating Peptide by light transmittance aggregometry (LTA) and a percentage P2Y12 inhibition is calculated. ACC/AHA/SCAI Guidelines (2006) suggest that successful Plavix therapy is achieved when P2Y12 Inhibition is 50% or greater.
LIMITATIONS Hemolytic, Icteric, and Lipemic samples
NORMAL RANGE Interpretation
SAMPLE REPORT Upon request

Test Codes

CPT CODE 85576x4
LOINC CODE 5992-3, 13592-1, 53568-2, 13592-1, 21027-8