PLATELET FUNCTION ASSAY

Message

Hematology

Test Code

LAB318

Alias/See Also

PFA
Collagen/EPI
Collagen/ADP

CPT Codes
85576

Includes

The Collagen/Epinephrine (COL/EPI) Test Cartridge is the primary cartridge used to detect platelet dysfunction induced by intrinsic platelet defects, von Willebrand disease or exposure to platelet inhibiting agents.

The Collagen /ADP (COL/ADP) Test Cartridge is only reflexed if an abnormal result obtained with the COL/EPI Test Cartridge may have been caused by the effect of acetyl salicylic acid (ASA) or medications containing ASA.

Preferred Specimen

LAB WILL DRAW -- call Lab (HHN x45618 / HHI x73111) Draw a small red top as discard tube prior to collecting the blue tops. 6 mL whole blood (2-blue top tubes, citrate). Do NOT use butterfly for venipuncture. Do NOT use smaller than 21 G needle for venipuncture. Do NOT draw from a line.
Do NOT use Tube System to transport. Must hand-deliver to Laboratory.
Please affix "Do Not Spin" stickers to the samples if available.

Minimum Volume

6 mL

Instructions

Initial testing is for Collagen/Epinephrine. If results are abnormal, additional reflex testing for Collagen/ADP will be performed at an additional charge.

LAB: Do NOT centrifuge. Keep at Ambient: Test must be run within 4 hours of collection.

Transport Container

Ambient 4 hours

Transport Temperature

Ambient
Hand delivered to Laboratory
Do not use Pneumatic Tube

Specimen Stability

Testing must be completed within 4 hours of collection.

For Col/EPI test cartridge, it is recommended that testing not be performed until 10 to 30 minutes after blood collection.

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Hemolyzed or Lipemic Samples. Blood must not be spun or refrigerated.

Methodology
The PFA-100 system reproduces, in-vitro and under high shear, the conditions to which a platelet would be exposed to in an injured blood vessel. The instrument controls the environmental conditions of temperature and pressure. The aperture simulates the injured part of a blood vessel. The membrane is coated with collagen and an agonist, and is soaked with the Trigger Solution, which is dispensed at the beginning of the test. Similar to the in vivo mechanism, platelets adhere and aggregate at the aperture thereby gradually diminishing and finally arresting the blood flow. The instrument determines the time from the start of the test until the platelet plug fully occludes the aperture, and reports that as the Closure Time (CT). The CT is an indicator of the platelet function in the analyzed whole blood sample.

Setup Schedule

Draw between 7am and 7pm

Report Available

Testing available 7am - 7pm
Reports same shift.

Limitations

Many medications are known to affect platelet function. Therefore, the medication history of the patient should be reviewed if available.

Closure Time above the laboratory cut-off could reflect reduced platelet function caused by a hematocrit less than 30% or a platelet count less than 150,000 µL.

Reference Range

Collagen/Epinephrine: 80-184 seconds Collagen/ADP: 56-103 seconds

Clinical Significance

Platelet dysfunction detected by the PFA-100 system may be acquired, inherited, or induced by platelet inhibiting agents. The most common causes of platelet dysfunction are related to uremia, von Willebrand disease (vWD), and exposure to agents, such as acetyl salicylic acid (ASA, for example aspirin).

Platelet plug formation in the PFA-100 system is affected by low platelet counts and/or activity, inadequate plasma von Willebrand factor status, and additionally by inadequate hematocrit because of the flow process.

Results should always be evaluated in conjunction with clinical history and other laboratory findings. In cases where PFA-100 test results do not agree with the clinical assessment, additional testing should be performed.

Performing Laboratory
HHN/HHI

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.