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4 - 7 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
For more information, please view the literature below.
Blue-top (sodium citrate) tube
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 N° 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 Volume Guide for Coagulation Testing to ensure proper draw volume.
Do not draw from an arm with a heparin lock or heparinized catheter.
This assay is used to obtain a presumptive diagnosis of protein S deficiency while a patient is receiving antivitamin K therapy. Use of this assay is discouraged.
This assay may not detect rare qualitative types of protein S deficiency.
This procedure may be considered by Medicare and other carriers as investigational and, therefore, may not be payable as a covered benefit for patients.
Enzyme-linked immunosorbent assay (ELISA)
Because it is vitamin K dependent, the protein S level begins to decrease 60 hours after oral anticoagulant warfarin therapy is begun.6 When oral anticoagulant is stopped, its effects on protein S may be seen for up to two weeks or longer. For several days after surgery or a thrombotic event, the protein S levels may be diminished even in the absence of oral anticoagulants; during this period, assays cannot be used to establish a congenital deficiency. The total protein S antigen concentration assay:factor VII antigen concentration assay ratio may be used to determine a presumptive protein S deficiency in patients on oral anticoagulant therapy if clinical indications prevent suspension of therapy. A ratio ≤0.5 suggests protein S deficiency, however, deficiency cannot be ruled out when the ratio is ≥0.6, as a functional protein S deficiency will not be detected using this method.
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|500530||Protein S/FVII Antigen Ratio||500531||Protein S Antigen, Total||%||27823-4|
|500530||Protein S/FVII Antigen Ratio||500532||Factor VII Antigen**||%||49870-9|
|500530||Protein S/FVII Antigen Ratio||500533||Protein S Ag/FVII Ag Ratio**||ratio||18345-9|
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