INNOVANCE Free PS Ag Assay

Easy, specific, and stable protein S antigen testing

The Siemens Healthineers INNOVANCE Free PS Ag and Protein S Ac assays support differentiation between type I and type II protein S deficiencies. Combined with other Siemens Healthineers thrombophilia assays, the INNOVANCE Free PS Ag assay completes your lab's thrombophilia testing portfolio. Now you can obtain a broad thrombophilia testing solution from a single, trusted supplier, streamlining your ordering and administration processes. Benefit from excellent result correlation across Siemens Healthineers hemostasis testing platforms.

Several methods currently exist for determination of protein S. Functional assays such as protein S Ac assays measure protein S activity. In contrast, immunoassays measure different types of protein S antigen. Free protein assays measure free protein S only, while total protein S assays measure both free and bound protein S antigen. According to latest guidelines, the initial assay for congenital PS deficiency should be the free PS antigen assay.

• Before testing for protein S deficiency, causes of acquired deficiencies and for interfering factors should be assessed. Testing for congenital protein S deficiency on patients with acquired conditions is recommended to be deferred.
• Protein S deficiency was classified into three phenotypes (type I, II, and III) by Bertina in 1991 (during the ISTH-SSC meeting).
• A free protein S Ag assay is recommended as the initial assay for congenital Protein S deficiency. A total Protein S Ag assay can be performed to differentiate between type I and type III deficiency but is recognized to provide little clinical information. Protein S activity testing in a patient with a normal free protein S Ag result may be useful in case of strong clinical suspicion, to identify Protein S type II deficiency. Protein S activity is measured with a protein S Ac assay, an activated protein C (APC)-cofactor activity test using the factor Xa-pathway. It uses Russell’s viper venom (RVV) as a factor X-activator by adding protein S-deficient plasma and APC.
• If an abnormal value is obtained, testing must be repeated after at least 4 weeks for confirmation.
• There are different types of protein S activity and antigen assays^1,2 that generate different result levels. Samples from a given patient should always be measured with the same type of assay.
• The current protein S type II deficiency is an APC-cofactor deficiency. A deficiency in TFPIα-cofactor activity (single or pleiotropic with APC-cofactor) was recently described. To date, no cases of these subtypes have been reported. Moreover, its association with venous thromboembolism is not yet established.