Test Details
Methodology
Enzyme immunoassay (EIA)
Result Turnaround Time
2 - 4 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.
Use
This test is used for confirmation and characterization of protein C 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
Individuals with heterozygous PC deficiency may have low normal PC levels.7 Treatment with warfarin decreases the levels of vitamin K-dependent factors including PC. PC levels start to drop after six hours of warfarin treatment and do not regain pretreatment levels until generally two weeks after cessation of therapy. PC levels can become depleted as the result of activation of coagulation, limiting the utility of testing for congenital PC deficiency during the immediate convalescent period after a thrombotic event.7
This procedure may be considered by Medicare and other carriers as investigational and, therefore, may not be payable as a covered benefit for patients.
Custom Additional Information
See Protein C Deficiency Profile [283655] for more 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, except when the sample is collected using a winged (ie, "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 underfilling 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
Protein C levels tend to be lower in newborns but typically reach adult ranges by six months of age.6 Levels in some children remain low until 16 years of age.6
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
Footnotes
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 080465 | Protein C Antigen | 27820-0 | 080465 | Protein C Antigen | % | 27820-0 |
| Order Code | 080465 | |||||
| Order Code Name | Protein C Antigen | |||||
| Order Loinc | 27820-0 | |||||
| Result Code | 080465 | |||||
| Result Code Name | Protein C Antigen | |||||
| UofM | % | |||||
| Result LOINC | 27820-0 |