Overview: Protein S Functional TestIntroduction: The Protein S Functional Test measures Protein S activity to diagnose clotting disorders, causing excessive clotting. Aligned with 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 coagulation for patients with suspected Protein S deficiency or thrombophilia.
Other Names: Protein S Activity Assay, Functional Coagulation Test.
FDA Status: Laboratory-developed test (LDT), meeting coagulation standards for diagnostic accuracy.
Historical Milestone: Protein S functional testing began in the 1980s with thrombophilia research. Assay methods improved in the 2000s, enhancing diagnostic precision.
Purpose: Measures Protein S activity to diagnose clotting disorders, guides treatment, and evaluates patients with excessive clotting.
Test Parameters: 1. Protein S Activity
Pretest Condition: No fasting required. Collect plasma. Report history of excessive clotting or thrombophilia symptoms.
Specimen: 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 excessive clotting, thrombosis, or family history of clotting disorders. Include current medications, especially warfarin.
Consent: Written consent required, detailing the tests purpose, clotting disorder implications, and risks of sample collection.
Procedural Considerations: Uses chromogenic or clotting-based assays to measure Protein S activity. Results are available in 1-2 days, supporting clinical decisions. Performed in laboratories, often for clotting disorder diagnosis.
Factors Affecting Result Accuracy: Improper sample storage or anticoagulation therapy can affect results. Vitamin K deficiency may lower activity.
Clinical Significance: Low Protein S activity confirms deficiency, guiding anticoagulant therapy. Normal activity may require genetic testing.
Specialist Consultation: Consult a hematologist for result interpretation and treatment planning.
Additional Supporting Tests: Protein S antigen tests, D-dimer, or thrombophilia genetic panel 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, Esmon CT, 2022.
