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PFA - Bleeding Time


The Platelet Function Screen does not necessarily predict bleeding at surgery. An abnormal test result may not be associated with excessive bleeding. Conversely, a normal test result may exist in the setting of interaoperative or post surgical bleeding.

Patients with low hematocrits (<35%) or low platelet counts (<150,000) may show falsely abnormal platelet function with this test method. Patients with hematocrits <35% or platelet counts less than 150,000 may exhibit prolonged results. Platelet inhibiting drugs, such as aspirin, and anti-glycoprotein IIb/IIIa antagonists directly affect platelet function. Certain dietary fatty acids and lipids are known to inhibit platelet function. Hemolysis and an elevated erythrocyte sedimentation rate (ESR) may interfere with results.

Specimen Collection Requirements


Whole Blood, two light blue (3.2% buffered sodium citrate) top tubes


See Coagulation Specimen Collection Guidelines

For PFA specimens:

  • Sample must be gently inverted four times, immediately following collection.
  • Transport in an upright position without disruption.
  • DO NOT transport sample via pneumatic tube system.
  • It should be received in the Legacy Good Samaritan Hematology Lab within 2 hours of collection. 
  • Specimen must be tested within 4 hours.
  • All samples must be transported STAT directly to the Legacy Good Samaritan Hematology Lab.

Preferred Volume

6.0 mL

Minimum Volume

3.0 mL


Ambient (15-25°C) within 2 hours

Rejection Criteria

Clotted samples, samples collected in containers other than 3.2% buffered sodium citrate, tubes filled less than 90%, samples from patients with a Hematocrit greater than 55%, hemolyzed samples due to ex-vivo causes (i.e., difficult draw, poor sample draw), whole blood samples that were frozen before processing


WHOLE BLOOD: Ambient: 4 hours

Note: The test takes a minimum of 1 hour to perform and must rest for 30 minutes after transit and prior to testing. Thus specimens need to be in the Good Samaritan Hematology Lab optimally within 2 hours of collection.

Testing Information


7 days/week


Same day


Whole blood platelet adhesion and platelet aggregation

Reference Values

Reference Values

COL/EPI Borderline:      153-170 seconds
COL/ADP Borderline:    108-120 seconds

COL/EPI:    80-152 seconds
COL/ADP:  53-107 seconds
(Most Common):

Normal Platelet Function
COL/EPI Normal
COL/ADP Normal

Consistent with drug-induced platelet dysfunction
COL/EPI Abnormal
COL/ADP Normal

Intrinsic platelet dysfunction; further studies are indicated
COL/EPI Abnormal
COL/ADP Abnormal

NOTE: Other interpretive comments may be used as test results indicate.

CPT Codes


Last Updated: Wednesday, December 6, 2017 02:13:56 PM

Client Services: 503-413-1234