ARUP's Laboratory Test Directory

Protein C, Functional : 0030113

Mnemonic: PROT C F

Ordering Recommendation: Recommended test to detect protein C deficiency. Do not order if individual has been on warfarin in the previous 2-4 weeks.
Methodology: Clotting
Performed: Sun-Sat
Reported: 1-2 days
Specimen Required: Collect: Lt. 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.

Remarks:

Unacceptable Conditions: Serum. Non-frozen or hemolyzed specimens.

Stability (collection to initiation of testing): Ambient: 4 hours; Refrigerated: Unacceptable; Frozen at -20°C: 3 months, at -70°C: 6 months
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: 56-144%
10-11 years: 59-143%
12-13 years: 57-142%
14-15 years: 56-162%
16-17 years: 68-154%
18 years and older: 77-173%
Interpretive Data: Patients on warfarin may have decreased protein C values. Patients should be off warfarin therapy for two weeks for accurate measurement of protein C levels. Artificially increased functional protein C values may be due to heparin therapy or the presence of direct thrombin inhibitors or factor Xa inhibitors.
CPT Code(s): 85303
Cross References: Protein C Activity (Protein C Functional)