Protein S Deficiency

Junior (College 3rd year) ・Healthcare&Medicine ・MLA ・3 Sources

The liver and endothelial cells synthesise a vitamin K-dependent glycoprotein called Protein S which they store in the platelets. In the natural anticoagulant system, one of the roles of protein S is to function as a cofactor for Activated Protein C (APC). Protein S-APC complex proteolytically inactivates procoagulant factor Va to factor V, and procoagulant factor VIIIa to VIII as the coagulation flowchart below shows. Another function of protein S is to act directly as an anticoagulant independent of APC by inhibiting the formation of tenase complexes and prothrombin. Protein S exists either free in plasma or complexed to C4b-binding protein. Scientists discovered protein S in 1977 in Seattle, Washington (Comp et al. 2082).

Reason and Circumstances for Testing

2 to 6% of people with venous thrombosis have a congenital autosomal dominant disorder called protein S deficiency. Patients with congenital protein S deficiency have ten times the risk of having venous thrombosis compared to healthy persons. Patients with this disease also experience possible arterial thrombosis, recurrent miscarriage, and complications of pregnancy like preeclampsia, stillbirth and intrauterine growth restriction (Fourrier et al. 816)
Fourrier et al. (817) argue that according to the levels of free protein S antigen, total protein S antigen, and the activity of protein S in plasma, there are three types of protein S deficiency. The dysfunctional (Type II) Protein S deficiency is less common than protein S deficiencies Type I and III. Type III protein S deficiency is however partly due to mutations in the binding region of C4b-BP within the protein S. We often do the test to relatives of diagnosed protein S deficient patients and to explain causes of repeated miscarriages.

Patient Criteria and Sample Types

Make sure the patient is not under treatment with warfarin for two weeks as it lowers protein S, and avoid therapy with heparin for two days before the test. We do not draw the specimen with a heparinized catheter or heparin lock. The analysis is performed on a fresh frozen plasma sample or on whole blood collected in a light blue top tube that is buffered with 3.2% sodium citrate (Comp et al. 2082).

Method and Principle of the Test

The test is on the principle of latex immunoassay. Collect citrated plasma samples by double centrifugation. Collect blood in a blue-topped tube that contains 3.2% sodium citrate. Make sure to adjust the volume of citrate if a patient’s hematocrit is above 55%. Ensure a proper blood to the anticoagulant ratio, by ensuring the collection tubes are filled (Schwartz et al. 1297).
Mix the samples immediately by gently inverting the tubes more than five times to ensure the anticoagulant and the blood mix adequately. Centrifuge for ten minutes and then remove two-thirds of plasma carefully using a plastic transfer pipette without disturbing the cells Deliver the plasma to a plastic transport tube, cap the top, and then centrifuge for ten more minutes. With a second plastic pipette, remove the plasma careful not to disturb the platelets at the bottom of the tube. Transfer the pipetted plasma into a LabCorp PP transpak frozen purple tube and tighten the screw cap. Immediately freeze the plasma and keep it frozen till tested (Schwartz et al. 1297).

Interpretation and Result Analysis

In the average population, the values of protein S vary widely and are sex and age-dependent. Free protein S antigen is the initial test for protein S deficiency and when below age-sex standard range, we do total plasma protein S antigen (Schwarz et al. 1298). Table 1.1 shows the different heterozygous protein S deficiencies. Homozygous protein S deficiencies are rare.

1.1 Heterozygous Protein S Deficiencies

Table 1.2 has normal ranges for protein S antigen levels for different sexes and age. According to Schwarz et al., measurement of free protein S antigen levels, total protein S antigen levels, and protein S activity are used differentiating the various congenital protein S deficiencies (1299). If any of them is low, then a protein S deficiency exists and is distinguished using the above table.

Works Cited

Comp, P. C., et al. ""Familial protein S deficiency is associated with recurrent thrombosis. Journal of Clinical Investigation 74.6 (1984): 2082.
Fourrier, François, et al. ""Septic shock, multiple organ failure, and disseminated intravascular coagulation: compared patterns of antithrombin III, protein C, and protein S deficiencies. Chest 101.3 (1992): 816-823.
Schwarz, Hans Peter, et al. ""Plasma protein S deficiency in familial thrombotic disease. Blood64.6 (1984): 1297-1300.

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