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Confirmation and characterization of protein C deficiency.
Individuals with heterozygous PC deficiency may have low normal PC levels.6 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. Elevated factor VIII levels, as can be seen in acute phase reaction, can normalize the aPTT and effectively reduce PC levels.7 PC levels can be falsely low in patients with the factor VLeiden mutation. 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.6 Heparin therapy up to 1 unit/mL does not affect PC levels.6 This test should not be used for patients receiving thrombin inhibitors such as hirudin and argatroban.7
See Protein C Deficiency Profile [283655] for more clinical information.
1. Adcock DM, Kressin DC, Marlar RA. Effect of 3.2% vs 3.8% sodium citrate concentration on routine coagulation testing. Am J Clin Pathol. 1997 Jan; 107(1):105-110. PubMed 8980376
2. Reneke J, Etzell J, Leslie S, Ng VL, Gottfried EL. Prolonged prothrombin time and activated partial thromboplastin time due to underfilled specimen tubes with 109 mmol/L (3.2%) citrate anticoagulant. Am J Clin Pathol. 1998 Jun; 109(6):754-757. PubMed 9620035
3. National Committee for Clinical Laboratory Standardization. Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays; Approved Guideline. 5th ed. Villanova: NCCLS; 2008. Document H21-A5:28(5)
4. Gottfried EL, Adachi MM. Prothrombin time and activated partial thromboplastin time can be performed on the first tube. Am J Clin Pathol. 1997 Jun; 107(6):681-683. PubMed 9169665
5. McGlasson DL, More L, Best HA, Norris WL, Doe RH, Ray H. Drawing specimens for coagulation testing: Is a second tube necessary? Clin Lab Sci. 1999 May-Jun; 12(3):137-139. PubMed 10539100
6. Adcock DM, Bethel MA, Macy PA. Coagulation Handbook.
Aurora, Colo: Esoterix−Colorado Coagulation; 2006.
7. Van Cott EM, Laposata M. Coagulation. In: Jacobs DS, DeMott WR, Oxley DK, eds. Laboratory Test Handbook With Key Word Index. Hudson, Ohio: Lexi-Comp; 2001:327-358.
