Protein S Antigen (Free) Citrated Plasma Test
Protein S Antigen (Free) Citrated Plasma Test
The Protein S Antigen (Free) test measures the levels of free Protein S, a natural anticoagulant, in the blood. Protein S plays a crucial role in preventing excessive clot formation by regulating blood coagulation. This test is often used to evaluate individuals for clotting disorders, such as deep vein thrombosis (DVT) or pulmonary embolism (PE), and to diagnose Protein S deficiency, which may increase the risk of abnormal clotting.
What is the Protein S Antigen (Free) Test Used For?
This test may be recommended for individuals presenting with:
- Unexplained blood clots, such as DVT or PE
- Recurrent miscarriages
- Family history of Protein S deficiency or clotting disorders
- Symptoms of clotting disorders, including swelling, redness, and pain in the extremities or shortness of breath
Who Should Get Tested?
· You had an unexplained blood clot before 50 years of age
The healthcare provider may order a Protein S Antigen (Free) Citrated plasma test for you if
You had an unexplained blood clot before 50 years of age
You had a blood clot in an unusual location-like veins of your kidney, liver, or brain
You have had several blood clots
Your family member had an inherited protein C and S deficiency
Recurrent miscarriages
Before surgery
Preparation for the Test
The Protein S Antigen (Free) test requires a blood sample collected in a citrate tube. Proper preparation is essential for accurate results:
- Medication Disclosure: Inform your healthcare provider about anticoagulant therapy, as it may affect Protein S levels.
- Fasting: Fasting is generally not required, but follow any specific instructions provided by your doctor.
- Timing of Sample Collection: Avoid testing during active clotting episodes or shortly after starting anticoagulation therapy to prevent inaccurate results.
Interpretation of Results
Results are typically expressed as a percentage of normal Protein S levels. Key interpretations include:
- Normal Range: Varies slightly by laboratory but is generally between 60% and 150% of the reference range.
- Low Levels: May indicate Protein S deficiency, which can be:
- Inherited (Type I or Type III): Genetic mutations affecting Protein S production or activity.
- Acquired: Caused by conditions like liver disease, vitamin K deficiency, or autoimmune disorders such as lupus.
- High Levels: Rarely clinically significant but may occur in certain conditions.
Note: Results should be interpreted in the context of clinical symptoms, family history, and other laboratory findings.
FAQs
What is the difference between free and total Protein S?
Free Protein S is the active form that participates in anticoagulation, while total Protein S includes both free and bound forms. The free form is more clinically relevant in evaluating clotting disorders.
Can medications affect Protein S levels?
Yes, anticoagulants like warfarin, heparin, or direct oral anticoagulants (DOACs) can lower Protein S levels. Inform your doctor if you are on these medications.
How is Protein S deficiency treated?
Treatment focuses on managing clotting risk, often involving anticoagulant therapy and addressing underlying causes, such as vitamin K deficiency.
Can Protein S levels fluctuate?
Yes, levels may vary due to factors like acute illness, pregnancy, liver disease, or use of certain medications. Retesting may be needed for confirmation.
Is Protein S deficiency genetic?
Protein S deficiency can be inherited (autosomal dominant) or acquired due to other medical conditions or medications.
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