Protein S Activity Test
This test measures Protein S activity in a plasma sample using a clot detection method. Protein S deficiency, whether inherited or acquired, is associated with venous thrombosis.
About this test
Protein S activity is measured in 1 mL of frozen plasma, collected in a sodium citrate (light blue-top) tube, using a clot detection method. The test reports how well Protein S is functioning rather than simply how much is present.
Protein S deficiency, whether congenital or acquired, is associated with venous thrombosis, which is why this test may be considered in that context. Acquired deficiency may occur with vitamin K antagonist medications or vitamin K deficiency, liver disease, malignancy, consumptive DIC, surgery, trauma, hepatic immaturity in a newborn, or physiologically during pregnancy.
Test details
| Quest code | 1779 |
|---|---|
| Methodology | Clot Detection |
| Sample type | 1 mL frozen plasma |
| Collection | Quest patient service center |
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Additional details
What this test looks at
The test reports one value: how well Protein S is functioning in a plasma sample, measured with a clot detection method. Because anticoagulant medications can affect the result -- vitamin K antagonists such as warfarin may lower measured activity, heparin may have no effect or falsely raise it at higher levels, and direct thrombin or factor Xa inhibitors may falsely raise it -- a clinician takes any anticoagulant therapy into account when reading the result. Quest also lists this test under the name Protein S, Functional.
Order online and a physician order is included — no doctor's visit and no insurance needed. Your sample is collected at a Quest Diagnostics patient service center.
Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.
Frequently asked questions
What does the Protein S Activity test measure?
It measures how well Protein S is functioning in a plasma sample, using a clot detection method.
How is the sample collected?
Through a blood draw that collects 1 mL of plasma into a sodium citrate (light blue-top) tube, which is then frozen for testing.
Do I need to prepare for this test?
No preparation instructions are listed for this test, though people follow any instructions their ordering clinician provides.
Can medications affect a Protein S Activity result?
Yes. Vitamin K antagonists such as warfarin may decrease measured activity, heparin may have no effect or falsely increase it at higher levels, and direct thrombin or factor Xa inhibitors may falsely increase it.
What does a Protein S Activity test cost without insurance?
$409. Celio Health's price is a flat cash price and insurance is never billed: the required physician's order is included.