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Lab Manual for Moffitt-Long and Mount Zion

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Protein C, Activity

Item Value
Approval req'd? No
Available Stat? No
Test code PRC
Test group Protein C
Performed by Parnassus Hematology
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.

Patient should not be receiving aprotinin which will result in underestimation of Protein C.

If "Protein C" is requested without further specification a protein C activity will be performed.

For patients with Hct's ≥ 55% please contact Hematology (x3-1747) 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 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UCSF Rejection Criteria Samples collected in outdated blue top vacutainer.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
Processing notes Deliver sample asap to Hematology for processing.

Test specimens within four hours of collection or freeze plasma in a plastic tube at -20C.

If Protein C Antigen is ordered on the same specimen, 4.5 mL suffices for both tests.
Units %
Normal range
Infant 0-6 months Not determined (See Additional information)
Child 6 months - 16 years Not determined (See Additional information)
> 16 years 76-146%
Turn around times 2-4 weeks
Additional information There is no published pediatric reference range for Protein C activity, which generally parallels the level of Protein C Antigen. The following table gives age-adjusted reference ranges for Protein C antigen for a full term infant:

Day 1 Day 5 Day 30 Day 90 Day 180
17-53% 20-64% 21-65% 28-80% 37-81%


Reference: Andrew M. Et al. Development of the Human Coagulation System in the Full Term Infant. Blood July 1987, 70(1):165-172

The following table gives age-adjusted reference ranges for Protein C antigen for a child:
1-5 years 6-10 years 11-16 years
40-92% 45-93% 55-111%


Reference: Andrew M. Et al. Maturation of the Hemostatic System During Childhood. Blood October 1992, 80 (8): 1998-2005.

Results may be altered by coumadin like Rx and presence of Aprotinin.

A low level of protein C may be associated with an inherited deficiency or with secondary causes such as warfarin therapy, acute venous thrombosis, recent surgery, liver disease, vitamin K deficiency, disseminated intravascular coagulation, and L-asparaginase therapy.

Aprotinin in the sample can result in under-estimation of the protein C level.

If unusual findings are noted a pathologist review and interpretation may be performed and separately billed for
LOINC code 27819-2
Last Updated 4/1/2014 11:38:07 AM
Entry Number 793
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