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Platelet Neutralization Procedure

PNP, Platelet Neutralization Procedure (PNP)

Test Codes

EPIC: LAB5203, PNP

Department

Coagulation

Instructions

• This test is not an orderable test. It is part of the Inhibitor Anticoagulant Screen confirmation only.
• This test will not be performed on patients receiving heparin.
• Specimens with hematocrit values greater than 55% must have anticoagulant adjusted. Specimens must be re-collected using a specified whole blood to sodium citrate ratio. Contact the performing Laboratory for specific instructions.

Specimen Collection Criteria

Collect: One Light Blue-top 3.2% Sodium Citrate tube.

TUBE MUST BE FULL.

Physician Office/Draw Specimen Preparation

For optimal results, maintain whole blood specimen at room temperature (20-26°C or 68-78.8°F) prior to transport. Transport whole blood to the Laboratory within 4 hours of collection. If transport within 4 hours is not possible, the following procedure must be followed for accurate results:

1. Centrifuge the capped tubes at 1500 x g for 15 minutes.
2. Transfer plasma with plastic pipette into a plastic polypropylene centrifuge tube, cap and centrifuge an additional 15 minutes at 1500 x g to obtain platelet poor plasma (PPP) which has a platelet count less than 10 bil/L. Plasma with a platelet count of less than 10 bil/L is critical for accurate results.
3. Immediately remove only the top two-thirds of the PPP and transfer into a screw cap, 5 ml, 75 x 13 mm, round base, polypropylene tube.  
4. Freeze (-20°C/-4°F or below) the PPP immediately.
5. Transport frozen on DRY ICE. Specimen must remain frozen during transport.    

Preparation for Courier Transport

Transport: Whole blood at room temperature (20-25°C or 68-77°F), or plasma obtained through the process listed above, frozen (-20°C/-4°F or below).

Rejection Criteria

• Glass tubes and 3.8% Sodium Citrate tubes.
• Specimens that are clotted or grossly hemolyzed.
• Inappropriate specimen volume.
• Thawed or partially thawed specimens.
• Specimens drawn from patients receiving heparin.

In-Lab Processing

Whole blood specimens must be processed as follows upon receipt in the Laboratory: 

1. Centrifuge the capped tubes at 1500 x g for 15 minutes.
2. Transfer plasma with plastic pipette into a plastic polypropylene centrifuge tube, cap and centrifuge an additional 15 minutes at 1500 x g to obtain platelet poor plasma (PPP) which has a platelet count less than 10 bil/L. Plasma with a platelet count of less than 10 bil/L is critical for accurate results.
3. Immediately remove only the top two-thirds of the PPP and transfer into a plastic tube.

4. Test or freeze specimen according to lab protocol.

Storage

Specimen Stability for Testing:

Whole Blood
Room Temperature (20-26°C or 68-78.8°F): 4 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Platelet Poor Plasma (PPP)
Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): 30 days

Specimen Storage in Department Prior to Disposal:

Frozen (-20°C/-4°F or below): 30 days

Laboratory

Royal Oak Coagulation Laboratory

Performed

Monday – Friday, 7:00 am – 3:30 pm.
Results available within one business day.

Reference Range

Negative.

Test Methodology

Change in Optical Density (IL ACL TOP Series). 

Interpretation

The platelet neutralization procedure (PNP) is based on the ability of platelet phospholipid to neutralize significantly in vitro lupus anticoagulant. The disrupted platelet membranes present in the freeze-thawed platelet suspension provide the phospholipid to neutralize phospholipid antibodies present in the plasma of patients with lupus anticoagulant. The clotting time of each test plasma/saline dilution is compared to the clotting time of the test plasma/platelet dilution. A correction of 5 seconds or more between the two results is indicative of the presence of a lupus anticoagulant.

Clinical Utility

This test can assist in the detection of lupus anticoagulant.

CPT Codes

85597

Contacts

Last Updated

4/21/2023