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Lab Dept:
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Coagulation
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Test Name:
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PROTEIN S, FREE
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General Information
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Lab Order Codes:
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PRSE
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Synonyms:
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Protein S; Protein S Free Antigen
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CPT Codes:
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85306 – Clotting inhibitors or anticoagulants; protein S, free
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Test Includes:
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Protein S Antigen, Free reported as a %.
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Logistics
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Test Indications:
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Protein S is a Vitamin K dependent plasma glycoprotein that serves as the cofactor for the anticoagulant function of activated Protein C inactivating activated Factors 5 and 8. Protein S deficiency is a risk factor for thromboembolism. Severe deficiency may cause purpura fulminans. Protein S circulates in plasma in two forms: 40% is free Protein S, 60% is bound to C4B binding protein. Only the Free has cofactor activity for Protein C. therefore, it is the preferred method for measuring Protein S.
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Lab Testing Section:
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Coagulation - Sendouts
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Referred to:
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Fairview University Medical Center (Test# PSF)
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Phone Numbers:
Minneapolis:
Saint Paul:
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612-813-6280
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651-220-6550
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Test Availability:
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Daily, 24 hours
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Turnaround Time:
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1 - 3 days, testing is performed 3 times per week.
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Special Instructions:
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A clean venipuncture is essential. INR is needed for interpretation. Protein S is decreased in Coumadin therapy/Vitamin K deficiency.
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Specimen
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Specimen Type:
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Whole blood
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Container:
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Light Blue top tube (Buffered Na Citrate 3.2%)
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Draw Volume:
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2.7 mL blood in a 3 mL tube
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Processed Volume:
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Specimen will be processed by reference lab facility.
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Collection:
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If the patient’s hematocrit is >55%, contact laboratory to obtain a special tube. Fill tube completely. Mix thoroughly by gentle inversion.
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Special Processing:
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Lab Staff: Do Not Centrifuge. Send in original Vacutainer® tube at room temperature. The specimen must arrive at Fairview reference lab within 24 hrs of draw.
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Patient Preparation:
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If the patient is being treated with Coumadin®, this should be noted. Coumadin® will lower Protein S.
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Sample Rejection:
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Improper tube, clotted sample; overfilled tube; underfilled tube, sample received more than 24 hrs after collection; mislabeled or unlabeled specimen
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Interpretive
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Reference Range:
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FRACTION
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SEX
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AGE
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RANGE (%)
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Protein S Free:
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Both (M/F)
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Newborn:
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33 – 67
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Both (M/F)
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1 – 4 days:
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24 – 48
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Both (M/F)
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5 – 29 days:
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36 – 64
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Both (M/F)
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30 – 89 days:
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48 – 78
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Both (M/F)
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90 days – 10 years:
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60 – 135
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Males:
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11 yr - Adult
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70 – 135
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Females:
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11 yr - Adult
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55 – 125
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Critical Values:
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N/A
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Limitations:
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Coumadin® will lower Protein S. Normal, full-term newborn infants or healthy premature infants may have decreased levels of total Protein S (15 – 30%), but because of low levels of C4bBP, free Protein S may be normal or near normal adult levels (≥50%). Total Protein S reaches adult levels by 80 – 180 days postnatal. There is evidence that functional deficiency of Protein S may occur in patients who have demonstrable Protein S antigen. Spurious low results may be obtained with plasma-based functional Protein S assay in patients who have activated Protein C resistance
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Methodology:
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Latex Immusorbent Assay (LIA)
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References:
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Fairview University Medical Center Web Page June 2011
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Harmening DH (1997) Clinical Hematology and Fundamentals of Hemostasis
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Updates:
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5/20/2004: As of March 1, 2004, Fairview University no longer performs the Protein S, total as part of this test. If there is a clinical need for this the total portion of Protein S, it can be ordered separately. Please contact the laboratory for more information.
Reference ranges for Protein S, total have been removed as well as other references for this test.
Draw volume changed from 4.5 mL to 2.7 mL blood.
5/3/2006: Reference range changes, previously listed as females ≥ 1 year: 65 – 125%, males ≥ 1 year: 75 – 135%
6/1/2007: Reference range changes, previously listed as females ≥1 year: 70 – 135%, males ≥1 year: 75 – 135%
7/24/2007: Reference changes, previously listed as females females ≥1 year: 65 – 125%, males ≥1 year: 55 – 135%
6/13/2011: Reference value changes, previously listed as females ≥1 year: 55 – 125%, males ≥1 year: 70 – 135%
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