Ordering Recommendation

Recommended test to detect protein S deficiency. Do not order if individual has been on warfarin therapy in the previous 2-4 weeks.

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation

Light Blue (Sodium Citrate). Refer to Specimen Handling at aruplab.com for hemostasis/thrombosis specimen handling guidelines.

Specimen Preparation

Transfer 1.5 mL platelet-poor plasma to an ARUP Standard Transport Tube. (Min: 1 mL)

Storage/Transport Temperature

CRITICAL FROZEN. Separate specimens must be submitted when multiple tests are ordered.

Unacceptable Conditions

Serum. EDTA plasma, clotted or hemolyzed specimens.


Ambient: 4 hours; Refrigerated: Unacceptable; Frozen at -20°C: 3 months, at -70°C: 6 months


Microlatex Particle-Mediated Immunoassay




1-3 days

Reference Interval

Age Male Female
1-89 days 15-55% 15-55%
90-179 days 35-92% 35-92%
180-364 days 45-115% 45-115%
1-5 years 62-120% 62-120%
6-9 years 62-130% 62-130%
10-17 years 60-140% 60-140%
18 years and older 74-147% 55-123%

Interpretive Data

Patients on warfarin may have decreased free protein S values. Patients should be off warfarin therapy for two weeks for accurate measurement of free protein S levels. Decreased levels of free protein S are also associated with DIC, liver disease, pregnancy, and inflammatory syndromes.

Compliance Category



Hotline History


CPT Codes



Component Test Code* Component Chart Name LOINC
0098894 Protein S Ag Free 27821-8
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


Protein S Free, Antigen