Test Details
Methodology
Latex immunoassay (LI)
Result Turnaround Time
2 - 3 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.
Test Includes
This test includes free protein S.
Use
This test is used for confirmation and characterization of protein S (PS) congenital deficiency.
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.
Limitations
The presence of rheumatoid factor may lead to an over-estimation of the free protein S level. The presence of anti-bovine albumin and/or anti-mouse antibodies in certain subjects may lead to an over-estimation of the free protein S level.
Custom Additional Information
See Protein S Deficiency Profile [117754] for additional clinical information.
Specimen Requirements
Specimen
Plasma, frozen
Volume
1 mL
Container
Blue-top (sodium citrate) tube
Collection 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 evacuated 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.
Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.
Stability Requirements
| Temperature | Period |
|---|---|
| Frozen | 28 days |
| Freeze/thaw cycles | Stable x3 |
Reference Range
| Age | Range |
| 1 d | 37–42% |
| 3 d | 40–57% |
| 1 to 11 m | 80–116% |
| 1 to 5 y | 63–120% |
| 6 to10 y | 83–123% |
| 11 to 16 y | 76–127% |
| >16 y | 60–145% |
Storage Instructions
Freeze.
Patient Preparation
Avoid warfarin (Coumadin®) therapy for two weeks and heparin therapy for two 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
References
Gupta A, Tun AM, Gupta K, Tuma F. Protein S Deficiency. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan. 2022 Dec 5. PubMed 31335064
Moore GW. Thrombophilia Screening: Not So Straightforward. Semin Thromb Hemost. 2024 Nov;50(8):1131-1152. PubMed 38733983
STA®- Liatest® Free Protein S Instructions For Use (IFU) [package insert]. July 2022.
Footnotes
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 164519 | Protein S, Free | 27821-8 | 164519 | Protein S, Free | % | 27821-8 |
| Order Code | 164519 | |||||
| Order Code Name | Protein S, Free | |||||
| Order Loinc | 27821-8 | |||||
| Result Code | 164519 | |||||
| Result Code Name | Protein S, Free | |||||
| UofM | % | |||||
| Result LOINC | 27821-8 |