Protein S Antigen
| Protein S Antigen | | | |
| Number | | 164517 |
| CPT | | 85305; 85306 |
| Related Information | | Hemostasis and Thrombosis Appendix Protein S Deficiency Profile Protein S:Factor VII Antigen Ratio |
| Test Includes | | Total protein S and free protein S |
| Special Instructions | | If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions. |
| Specimen | | Plasma, frozen |
| Volume | | 3 mL |
| Minimum Volume | | 2 mL |
| Container | | Blue-top (sodium citrate) tube |
Collection | | Blood should be collected in a blue-top tube containing
3.2% buffered sodium citrate.1 Evacuated
collection tubes must be filled to completion to ensure a
proper blood to anticoagulant ratio.2,3 The
sample should be mixed immediately by gentle inversion at
least six times to ensure adequate mixing of the
anticoagulant with the blood. A discard tube is not
required prior to collection of coagulation
samples.4,5 When noncitrate tubes are collected
for other tests, collect sterile and nonadditive (red top)
tubes prior to citrate (blue top) tubes. Any tube
containing an alternate anticoagulant should be collected
after the blue-top tube. Gel-barrier tubes and serum tubes
with clot initiators should also be collected after the
citrate tubes. Centrifuge and carefully remove the plasma
using a plastic transfer pipette, being careful not to
disturb the cells. Transfer the plasma into a LabCorp PP
transpak frozen purple tube with screw cap (LabCorp
No 49482). Freeze immediately and maintain
frozen until tested. To avoid delays in turnaround time
when requesting multiple tests on frozen samples, please
submit separate frozen specimens for each test requested.
Please print and use the Specimen
Collection Bulletin as a tube-filling guide. |
| Storage Instructions | | Freeze |
| Patient Preparation | | Avoid warfarin (Coumadin®) therapy for 2 weeks and heparin therapy for 2 days prior to the test. Do not draw from an arm with a heparin lock or heparinized catheter. |
| Causes for Rejection | | Gross hemolysis; clotted specimen; frozen specimen thawed in transit; improper labeling |
| Reference Interval | | Total: 58% to 150%; free: 56% to 124%. In newborns, total PS levels are lower than in adults (12% to 60%). Levels gradually reach adult ranges by 6 months of age.6 |
| Use | | Confirmation and characterization of protein S (PS) congenital deficiency |
| Limitations | | The presence of heparin or lupus anticoagulants leads to overestimation of PS. aPC resistance due to factor VLeiden mutation or some other cause can falsely lower measured PS activity levels.7 |
| Methodology | | Total PS is measured directly by enzyme immunoassay (EIA). Free PS is measured by EIA after C4b-BP complexed PS is precipitated out with polyethylene glycol. |
| Additional Information | | See Protein S Deficiency Profile [117754] for more clinical information. |
| Footnotes | | - Adcock DM, Kressin DC, and Marlar RA, “Effect of 3.2% vs 3.8% Sodium Citrate Concentration on Routine Coagulation Testing,” Am J Clin Pathol, 1997, 107(1):105-10.
- Reneke J, Etzell J, Leslie S, et al, “Prolonged Prothrombin Time and Activated Partial Thromboplastin Time Due to Underfilled Specimen Tubes With 109 mmol/L (3.2%) Citrate Anticoagulant,” Am J Clin Pathol, 1998, 109(6):754-7.
- “National Committee for Clinical Laboratory Standardization: Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays; Approved Guideline,” Third Edition, Villanova: NCCLS Document H21-A3:11(23), 1999.
- Gottfried EL and Adachi MM, “Prothrombin Time and Activated Partial Thromboplastin Time Can Be Performed on the First Tube,” Am J Clin Pathol, 1997, 107(6):681-3.
- McGlasson DL, More L, Best HA, et al, “Drawing Specimens for Coagulation Testing: Is a Second Tube Necessary?” Clin Lab Sci, 1999, 12(3):137-9.
- Van Cott EM and Laposata M, “Coagulation,” Laboratory Test Handbook With Key Word Index, Jacobs DS, DeMott WR, and Oxley DK eds, Hudson, OH: Lexi-Comp, 2001, 327-58.
- Adcock DM, Jensen R, Johns CS, et al, Coagulation Handbook, Esoterix Coagulation, 2002
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