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Test Code LAB318 Platelet Function Screen (PFA), Blood

Performing Laboratory

St. Louis Children's Hospital - Coagulation

Specimen Requirements

Patient Preparation: None

Container/Tube  
Preferred: Light blue-top (Citrate) tube (2.7 mL or 1.8 mL)

Note: if using 1.8 mL tube, two full tubes should be collected
Collection Volume: Tube(s) should be full. MINIMUM tube volume for collection is to marking on tube label but may go slightly above line

Submission Container/Tube: If specimen is coming from outside facility send to lab STAT keeping at ambient temperature.
Special Instructions: 

1. Platelet function test results are strongly dependent on the correct method of blood collection. Venipuncture should be performed using a 21-gauge or larger needle. Blood should be drawn directly into sodium citrate tube. Discard the sample if there is venous collapse or stoppage of blood flow during collection.

2.  

Draw a discard tube prior to light-blue top tube.

3.

Tube(s) should remain stoppered.

4.

Immediately invert tube/microtainer® gently 8-10 times after collection to ensure proper mixing of blood and anticoagulant (this will avoid specimen clotting). Deliver to lab promptly at ambient temperature only. DO NOT SEND THRU PNEUMATIC TUBE SYSTEM

5.

DO NOT underfill tube(s)

6.

SPECIMEN MAY NOT BE COLLECTED BY CAPILLARY METHOD

7.

If the patient has a known hematocrit >55%, contact the lab at 454-4268 for collection instructions and a specially adjusted collection tube(s).

 

Sample Rejection

Vacutainer®(s) that are under-filled

Clotted specimens

Grossly hemolyzed specimens

Specimens that are >4 hours old

Specimens sent thru the pneumatic tube system

Mislabeled or unlabeled specimens.

Logistics

Test Availability: Monday-Sunday
Cut-off time: None; performed as received
Turnaround Time: Same day; 1 hours from receipt in performing lab

Reference Values

Reference Interval: 

≥ 2 years:                          
   Collagen/ADP: 50-150 seconds
   Collagen/Epinephrine (EPI) 70-170 seconds                                                        
NOTE: ranges do not exist for newborn up to 2 years of age

Critical Value:  None established

Methodology

Platelet Adhesion to Biochemically Active Membranes

Limitations

  • Specimens with hematocrit levels >50% or platelet counts >500,000 have not been evaluated
  • Many medications are known to affect platelet function. Therefore, the medicatio history of the patient should be reviewed. Platelet inhibiting agents, such as Aspirin and anti-glycoprotein IIb/IIIa antagonists, directly affect platelet function.
  • Certain fatty acids and lipids found in various human diets are known to inhibit platelet function, for which the PFA-100 system was designed to detect. Neutral lipids, such as cholesterol, generally have not affect on platelet function. Physicians may wich to advise patients to refrain from fatty foods prior to testing.
  • Presence of hemolysis may interfere with test results.
  • The PFA-100 system performance has not been established for platelet inhibiting agents other than acetly salicylic acid.
  • Results of this test should always be interpreted in conjunction with the patient's medical history, clinical presentation, and other findings.

Additional Information

FOR SLCH CORE LABORATORY USE ONLY

Lab Processing Instructions: DO NOT SPIN. Check that correct sample volume has been collected and give to hematology bench.
Processed Volume: Blood level should be to line on label (may be over)
Analyte Stability:

Specimen Type Temperature    Time
Whole Blood (unprocessed)   Ambient 4 hours
    Refrigerated  DO NOT refrigerate   
  Frozen   DO NOT freeze   

Test Classification and CPT Code

85576x2

LOINC

ADP: 49010-2

EPI: 5996-4

Last Reviewed

06/2025