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Lab Manual for UCSF Clinical Laboratories

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If you have additional questions regarding this test, please call: 415-353-1667

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Protein S Activity

Item Value
Approval req'd? No
Available Stat? No
Test code PSACT
Test group Protein S
Performed by UC Davis
Sendout? Yes
Method Clot detection
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.

Avoid hemolysis

For patients with Hct's ≥ 55% please contact Hematology (415-353-1747) to obtain blue top tubes with adjusted citrate volumes in order to maintain the proper citrate to plasma ratio for coagulation studies.
Container type Blue top filled to full extent of vacuum
Amount to Collect 2.7 mL blood
Sample type Citrated plasma
Preferred volume 1.5 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UCSF Rejection Criteria Samples collected in outdated blue top vacutainer.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 Hemolyzed.
Processing notes This test is rarely necessary, most requests for Protein S should be ordered as PRSI unless 'activity' is explicitly included in the test request.

Deliver sample to Hematology ASAP for processing.

Separate and freeze plasma at -20C. Order Quest # 58891P
Ref Lab Rejection Criteria Received thawed.
Units % activity
Normal range Age
Newborn - Day 4 12-60%
Day 5 - 1 Month 22-78%
1 Month - 3 Months 33-93%
3 Months - 6 Months 54-118%
> 6 Months 70-119%
Stability Room temperature unacceptable, refrigerated unacceptable, frozen at -20C 2 weeks
Turn around times Run once per week. Turnaround 6-10 days
Additional information Test may be useful when there is a normal Free protein S level but persistent clinical suspicion for Hereditary Protein S deficiency.

A Free Protein S Antigen and a Protein S Activity should be ordered on the same specimen when a Protein S activity is requested. If only a Protein S Activity is requested, a Free Protein S Antigen will be performed.
CPT coding 85306-90
LOINC code 27822-6
Last Updated 6/24/2016 12:24:09
Entry Number 1091
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