Test Overview

Test Methodology

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Test Usage

Study to determine Protein C or Protein S causes of venous thrombosis.

Reference Range*

Interpretive report provided for abnormal results

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations

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Test Details

Days Test Performed


Analytic Time

7 days

Soft Order Code


Test Updated

Update Type: New Tests

Updated Date: 04/09/2020



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Specimen Requirements

Offsite Collection Instructions

Collect specimens in 3 blue top (citrate 3.2%) tubes. Mix by inversion. Specimens should arrive at the lab within 3 hours of collection; transport at room temperature. Alternatively, centrifuge, aliquot plasma into 3 plastic tubes, and freeze the specimen within 4 hours of collection. Transport frozen specimens on dry ice. Collection of the blood through lines that have been previously flushed with heparin should be avoided. If the blood must be drawn through a VAD (vascular access device), the line should be flushed with 5 mL of saline and the first 5 mL of blood or six dead space volumes of the VAD discarded.

Please provide clinical history (brief description of the reason for testing, e.g., history of easy bruising and menorrhagia, family history of von Willebrand disease) and a listing of current and recent medications, including oral contraceptives, anticoagulants, and factor replacement therapy/DDAVP.

Rejection Criteria

Specimens will be rejected if not properly filled, clotted, grossly hemolyzed, or contaminated with heparin.


Not indicated for patients receiving anticoagulant therapy, or immediately following an acute thrombotic event.


Blue Top Tube

Normal Volume

3 full 2.7mL tubes or 7mL plasma (three 1mL aliquots)

Minimum Volume

3 full 1.8mL tubes or 7mL plasma (three 1mL aliquots)

Additional Information

Panel designed for MLabs clients includes Activated Protein C Resistance Assay, Protein C Activity, and Protein S Antigen, Free. Test may include pathologist interpretation of results at an additional charge. By ordering this test, the clinician acknowledges that a pathologist interpretation will be performed and billed as a separate additional charge if indicated.

Billing Information

Fee Codes

CPT Code


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