Ordering Recommendation

Acceptable panel to detect and subtype protein C and S deficiencies. Do not order if the 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

Lt. blue (sodium citrate). Refer to Specimen Handling at aruplab.com for hemostasis/thrombosis specimen handling guidelines.

Specimen Preparation

Transfer 4 mL platelet-poor plasma to an ARUP Standard Transport Tube. (Min: 2 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


Electromagnetic Mechanical Clot Detection/Enzyme-Linked Immunosorbent Assay/Microlatex Particle-Mediated Immunoassay




1-5 days

Reference Interval

Test Number
Reference Interval
  Protein C Functional
Age Reference Interval (%)
1-4 days 17-53
5-29 days 20-64
30-89 days 21-65
90-179 days 28-80
180-364 days 37-81
1-6 years 40-92
7-9 years 70-142
10-11 years 68-143
12-13 years 66-162
14-15 years 69-170
16-17 years 70-171
18 years and older 83-168

  Protein S Ag Free
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

Refer to report.

Compliance Category



If Protein C Functional is low, Protein C, Total Antigen will be added. If Protein S Free is low, Protein S Total Antigen will be added. Additional charges apply.

Hotline History


CPT Codes

85303; 85306; if reflexed add 85302; if reflexed, add 85305


Component Test Code* Component Chart Name LOINC
0030113 Protein C Functional 27819-2
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 C, Functional and Protein S Free
Protein C, Functional with Reflex to Protein C, Total and Protein S, Free with Reflex to Protein S, Total