One 4.5 mL light blue top tube (sodium citrate). Collect by careful venipuncture to avoid tissue fluid contamination or hemolysis. Do not use needles smaller than 23 gauge. Fill tube to maximum draw, at least 90% full. Mix by gentle inversion. Call the Special Coagulation Department (541.687.2134 x4612) when urgent testing is needed in order to assure STAT testing. If patient HCT is >55%, collection into an adjusted volume of anticoagulant is required. Call the Routine Coagulation Department (541.687.2134 x4665) for instructions.
Refrigerate and keep capped in original tube if specimen will be received at the laboratory within 8 hours. If not, centrifuge to produce platelet-poor plasma, transfer to a plastic vial, and freeze immediately. Label with patient name, test, and ‘citrate.’ If multiple tests are ordered, freeze a separate aliquot for each test. Send to the laboratory within one week. NOTE: Separated plasma is stable for Protein C testing up to 48 hours if refrigerated. Freezing the specimen is recommended if it will not be received at the laboratory within 8 hours, in order to assure reliability of plasma for other coagulation testing which is often ordered on combination with this test.
Rapid processing is recommended, as Protein C testing is often shared with other more labile tests. Protein C is stable 8 hour ambient, 48 hours refrigerated, or 1 month frozen.
3 mL whole blood or 2 mL plasma.
1.8 whole blood or 0.5 mL plasma.
Original tube refrigerated if received at the laboratory within 8 hours; citrated plasma frozen on dry ice.
Coumadin therapy may depress Protein C levels. Do not screen for Protein C deficiency in patients who are taking coumadin. Levels obtained 2-3 months after acute thrombosis and when off anticoagulation for at least 2 weeks provide a true basal level. See also: Coagulation Study, Thrombosis Evaluation, Venous (25911) .