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The REAADS Protein S Antigen Test Kit is an in vitro diagnostic assay for the quantitative determination of Total and Free Protein S levels in human plasma (as a percentration) by enzyme-linked immunosorbent assay (ELISA). Plasma levels of Protein S may be used in conjunction with the results from other assays as an aid in diagnosing congenital or acquired Protein S deficiencies associated with thrombotic disease.

The REAADS Protein S Antigen Test Kit is a sandwich enzyme linked immunosorbent assay (ELISA). A capture antibody specific for human Protein S is coated to 96-microwell polystyrene plate. Diluted patient plasma is incubated in the wells, allowing any available Protein S to bind to the anti-human Protein S antibody on the microwell surface. The plates are washed to remove any unbound plasma molecules. Bound Protein S is quantitated using an HRP conjugated anti-human Protein S detection antibody. Any unbound conjugated antihuman Protein S is washed away after an incubation period. A chromogenic substrate of tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2) is added to develop a colored reaction. The intensity of the color is measured spectrophotometrically at 450nm in optical density (O.D.) units. Protein S relative percent concentrations in patient plasma are determined against a curve prepared from a reference plasma provided with the kit. Results obtained from diluted plasma samples not pretreated with polyethylene glycol (PEG) represent the Total Protein S concentration from that sample. To measure Free Protein S, PEG is added to plasma samples prior to beginning the assay to precipitate the Protein S-C4b binding protein complex. The supernatant fraction containing Free Protein S may be tested along with the untreated plasma sample. Both Total (untreated) and Free (PEG-treated) Protein S concentrations are determined following the same assay procedure described using separate reference curves.

1. Table of Acceptance Criteria and Reported Device Performance:

2. Sample Size Used for the Test Set and Data Provenance:

   • Sample Size: Not specified in the provided text, only referred to as "clinical samples."
   • Data Provenance: Not specified in the provided text. It is unclear if it's retrospective or prospective or the country of origin.

3. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications:

   • Not applicable. The study compares the new device to existing legally marketed predicate devices, not against expert-established ground truth for diagnosis/classification.

4. Adjudication Method for the Test Set:

   • Not applicable. The study is a comparative performance study against predicate devices, not one requiring adjudication of diagnostic outcomes.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study:

   • No, a MRMC study was not done. The study compares the performance of the new device against predicate devices using quantitative measurements of Protein S levels.

6. Standalone Performance (Algorithm only without human-in-the-loop performance):

   • Yes, this is a standalone performance study. The REAADS Protein S Antigen Test Kit is an in vitro diagnostic assay that produces quantitative results directly. Human intervention is involved in conducting the assay and interpreting the results in a clinical context, but the performance evaluation here specifically focuses on the accuracy of the assay itself in determining Protein S levels compared to existing methods.

7. Type of Ground Truth Used:

   • The "ground truth" for this study is the results obtained from legally marketed predicate devices: the Helena Protein S Antigen Rocket EID Method and the Helena Free Protein S Reagent. The study aims to demonstrate substantial equivalence to these established methods.

8. Sample Size for the Training Set:

   • Not applicable. This is not a machine learning model, so there is no "training set." The device is a laboratory assay.

9. How the Ground Truth for the Training Set Was Established:

   • Not applicable, as there is no training set for this type of device.

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