Test Overview

Test Methodology

Latex Immunoturbidometric

Test Usage

Used to identify and quantitate a Protein S defect or deficiency in those patients subject to recurrent venous thrombosis or pulmonary emboli.

Reference Range*

Males: 73 - 130%; Females: 65 - 139%.

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

Test Details

Days Test Performed


Analytic Time

2 hours

Soft Order Code


MiChart Code

Protein S Antigen, Free




+ See More



Looking to Order a Test?

We’ve provided helpful links to make ordering easy.

Find a Requisition

All specimens should be accompanied by a requisition.

Submitting Specimens

Learn about how to properly label and where to ship specimens.

Order Kits and Supplies

MLabs provides all the supplies necessary for the collection of specimens.

Test FAQ

Visit our provider FAQ and learn about common questions to ordering tests.

Specimen Requirements

Offsite Collection Instructions

Collect specimen in a blue top (citrate 3.2%) tube. Mix by inversion. Specimen should arrive at lab within 3 hours of collection; transport at room temperature. Alternatively, centrifuge, aliquot plasma into a plastic vial, and freeze the specimen within 4 hours of collection. Transport frozen specimen 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.

Rejection Criteria

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


This test is not indicated in patients receiving Coumadin (warfarin) therapy.


Blue Top Tube

Normal Volume

Full 2.7mL tube or 1mL plasma aliquot

Minimum Volume

Full 1.8mL tube or 1mL plasma aliquot

Additional Information

Protein S is a vitamin K dependent anticoagulant protein synthesized in the liver (and endothelium). Protein S circulates in plasma alone ("free") or reversibly bound to the complement regulatory protein C4b binding protein (C4bBP). C4bBP is an acute phase reactant and may be increased in inflammatory conditions, causing an acquired decrease of free protein S. Only free protein S has anticoagulant activity.

Billing Information

Fee Codes

CPT Code




Have More Billing Questions?

Explore our helpful billing resources:

Billing Resources

Billing FAQ