Overview: Protein S Free Antigen TestIntroduction: The Protein S Free Antigen Test measures free Protein S to diagnose clotting disorders, causing thrombosis. Following 2023 ISTH guidelines, it uses immunoassays for high specificity, supporting coagulation screening. This test is critical for guiding diagnosis, treatment planning, and improving outcomes in immunology for patients with suspected Protein S deficiency or thrombophilia.
Other Names: Protein S Free Assay, Free Coagulation Protein Test.
FDA Status: Laboratory-developed test (LDT), meeting immunology standards for diagnostic accuracy.
Historical Milestone: Protein S free antigen testing began in the 1990s with thrombophilia research. Immunoassay methods improved in the 2000s, enhancing diagnostic precision.
Purpose: Measures free Protein S to diagnose clotting disorders, guides treatment, and evaluates patients with thrombosis.
Test Parameters: 1. Protein S Free Antigen
Pretest Condition: No fasting required. Collect serum or plasma. Report history of thrombosis or clotting disorders.
Specimen: Serum (SST, 2-5 mL), Plasma (NaCit, 2-4 mL). Transport in a biohazard container.
Sample Stability at Room Temperature: 8 hours
Sample Stability at Refrigeration: 7 days
Sample Stability at Frozen: 6 months
Medical History: Document thrombosis, family history of clotting disorders, or cardiovascular events. Include current medications, especially warfarin.
Consent: Written consent required, detailing the tests purpose, clotting disorder implications, and risks of sample collection.
Procedural Considerations: Uses enzyme-linked immunosorbent assay (ELISA) to measure free Protein S levels. Results are available in 1-2 days, supporting clinical decisions. Performed in laboratories, often for clotting disorder diagnosis.
Factors Affecting Result Accuracy: Sample hemolysis or improper storage can affect results. Anticoagulants may lower free Protein S.
Clinical Significance: Low free Protein S confirms deficiency, guiding anticoagulant therapy. Normal levels may require functional testing.
Specialist Consultation: Consult a hematologist for result interpretation and treatment planning.
Additional Supporting Tests: Protein S functional test, Protein S total antigen, or genetic testing to confirm clotting disorder diagnosis.
Test Limitations: Non-specific for certain clotting disorders; clinical correlation is needed. Sample quality affects sensitivity.
References: ISTH Thrombophilia Guidelines, 2023; Journal of Thrombosis and Haemostasis, Comp PC, 2022.
