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Protein S-Functional
Test Code164525
Alias/See Also
Functional Protein S; Protein S Activity
CPT Codes
85306
Preferred Specimen
Plasma
Minimum Volume
1mL
Instructions
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 unless the sample is collected using a winged (butterfly) collection system. With a winged blood collection set a discard tube should be drawn first to account for the dead space of the tubing and prevent under-filling of the evacutated tube.(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 alternative 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. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested. Print and use the Specimen Collection Bulletin as a tube-filling guide.
Transport Container
Blue-top (sodium citrate) tube
Transport Temperature
Freeze
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis; clotted specimen; frozen specimen thawed in transit; improper labeling
Methodology
The patient plasma is added to PS-depleted normal plasma with normal levels of all factors but PS. The mixture is supplemented with excess aPC and factor V is added then. The extent of prolongation of the time to clot formation after calcuim chloride is added is proportional to plasma PS activity.
Setup Schedule
Daily 1st and 3rd shift
