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Protein S, free

Item Value
Approval req'd? No
Available Stat? No
Test code PRSI
Test group Protein S
Performed by Parnassus Hematology
Method Immunoturbidimetric
Collection Instructions 1. Check the expiration date on the label of the blue top vacutainer before drawing the patient.

2. For blood collection in a sodium citrate blue top, the tube must be filled to above the Minimum Fill Indicator on the tube. It is crucial to wait and allow the tube to stop filling before removing it from the needle.

3. With use of a butterfly needle, draw about 1 cc using a separate blue top to remove air from tubing, discard the first tube and then draw a second blue top tube filled to the full extent of the vacuum.

4. Tubes should not be filled past the Maximum Fill dashed line by either using a syringe or removing the tube cap.

Draw only before institution of oral anticoagulant therapy or after a stable therapeutic regimen has been established.
Container type Blue top filled to full extent of vacuum
Amount to Collect 2.7 mL blood
Sample type Citrated plasma
Preferred volume 1 mL plasma
Min. Volume 0.5 mL plasma
UCSF Rejection Criteria Samples collected in outdated blue top vacutainer. Over-filled or under-filled tubes may be rejected
Processing notes This is the typical test that should be ordered when a request for Protein S is received unless it explicitly states 'Activity'. If 'activity' is specified order PSACT.

Deliver samples to Hematology asap for processing. Freeze plasma in 1 mL aliquots at -20C.
Units % activity
Normal range
0-6 month old Not established (see Additional information)
> 6 mo 53-137%
Synonyms Free Protein S antigen
Turn around times 2-4 weeks
Additional information There is no published pediatric reference range for Free Protein S antigen, which generally parallels the level of Total Protein S antigen, and from which the pediatric (< 6 months old) reference ranges given below are derived (Andrew M et al. Development of the Human Coagulation System in the Full Term Infant. Blood. 1987, 70: 165- 172).

Day 1 Day 5 Day 30 Day 90 Day 180
12-60% 22-78% 33-93% 54-118% 55-119%


A normal level does not exclude the possibility of an immunologically intact but dysfunctional protein.

A low level of free protein S may be associated with an inherited deficiency or with secondary causes such as warfarin therapy, acute venous thrombosis, recent surgery, lever disease, vitamin K deficiency, disseminated intravascular coagulation, L-asparaginase therapy, pregnancy, oral contraceptives, estrogen therapy, states of actue inflammation, lupus anticoagulants, and proteinuria.

If unusual findings are noted a pathologist review and interpretation may be performed and separately billed for
LOINC code 4677-1
Last Updated 4/1/2014 11:43:17 AM
Entry Number 799
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