Plasma Test Protein S – Total

Description of the Test

• The Protein S – Total Test measures the total amount of Protein S in plasma, a key protein involved in regulating blood clotting.

• Protein S works as a natural anticoagulant by assisting Protein C in controlling the clotting process.

• This test is primarily used to evaluate a person’s risk of developing abnormal blood clots, also known as thrombosis.

Purpose / Clinical Significance

• Helps detect Protein S deficiency, a genetic or acquired condition that increases the risk of venous thromboembolism (VTE).

• Assists in evaluating unexplained clotting events, especially in younger individuals.

• Used as part of a thrombophilia workup, especially for those with a family history of clotting disorders.

• Essential in identifying clotting issues in pregnant women or those with recurrent miscarriages.

Principle

• This test quantifies both free and bound forms of Protein S in the blood.

• Measurement is typically done using immunological methods that detect total levels regardless of activity.

• Total Protein S includes the portion that is functionally active and the portion bound to other plasma proteins.

Whom and Why Should Take This Test

• Individuals with a personal or family history of deep vein thrombosis (DVT) or pulmonary embolism (PE).

• Patients who have experienced unexplained blood clots, particularly at a young age or in unusual locations.

• Women with a history of recurrent pregnancy loss or complications related to blood clotting.

• People undergoing evaluation for inherited thrombophilia or clotting disorders.

• Individuals starting hormonal therapy, oral contraceptives, or long-term immobility may also benefit from baseline screening.

Specimen Requirements

• A blood sample is collected into a tube containing citrate anticoagulant to prevent clotting.

• The sample should be processed promptly and plasma separated to maintain result accuracy.

• Fasting is not mandatory but may be advised in specific clinical settings.

• Avoid testing during acute thrombosis or while on anticoagulants unless advised otherwise by a specialist.

Common Methods

• Immunoassay techniques are commonly used to measure total Protein S levels in plasma.

• Some labs may use ELISA (enzyme-linked immunosorbent assay) for precise quantitative analysis.

• In certain cases, clot-based functional assays may be run alongside the total test to assess activity.

Interpretation of Results

• Normal levels indicate an adequate amount of Protein S, suggesting balanced coagulation.

• Low levels may suggest Protein S deficiency, which can be inherited or acquired due to liver disease, vitamin K deficiency, or anticoagulant use.

• Results must be interpreted with caution during pregnancy, infections, or while on medications like warfarin that can artificially lower Protein S levels.

• Abnormal results often require correlation with clinical symptoms and further thrombophilia panel tests.

Reference Range

• The normal reference range may vary slightly by lab but is typically around 60–150% of standard activity or concentration.

• Levels below the lower limit may indicate deficiency and increased clotting risk.

• Age, gender, and physiological conditions like pregnancy can influence the range.

Limitations

• Levels can be temporarily reduced during acute thrombosis, inflammation, or illness, leading to false interpretations.

• Warfarin therapy significantly lowers Protein S levels, so testing should ideally be done after discontinuation.

• It does not measure functional activity of Protein S unless a specific functional assay is ordered.

• Not suitable as a standalone test—should be used in combination with other coagulation and genetic markers.

Follow-up Testing

• Free Protein S Test may be recommended to specifically measure the unbound, active portion of the protein.

• Protein C activity and Antithrombin III tests are often included in a complete thrombophilia panel.

• Genetic testing may be advised for inherited Protein S deficiency.

• Repeat testing is sometimes necessary after recovery from illness or after discontinuation of anticoagulants.

Conclusion
The Plasma Protein S – Total Test is a critical diagnostic tool for identifying individuals at risk of abnormal blood clotting. Especially in Dubai, where preventive health checks are gaining importance, this test is valuable for early detection of clotting disorders, particularly in those with a personal or family history of thrombotic events. It is also essential in evaluating pregnancy complications and in planning safe treatment for patients requiring hormonal therapies or surgeries.