(62 days)
The D-dimer (DDMR) method on the Stratus® CS STAT fluorometric analyzer is an in vitro diagnostic test for the quantitative measurement of cross-linked fibrin degradation products (D-dimer) in human citrated or heparinized plasma. The Stratus® CS DDMR method is intended for use as an aid in the diagnosis of venous thromboembolism (VTE) [deep vein thrombosis (DVT) or pulmonary embolism (PE)].
The Stratus® CS DDMR procedure is a two-site sandwich assay based upon solid phase Radial Partition Immunoassay (RPIA) technology. In this procedure, dendrimer linked monoclonal antibody is added to the center portion of a square piece of glass fiber paper in the DDMR TestPak. This antibody recognizes a distinct antigenic site on the D-dimer molecule. Sample is then added onto the paper where it reacts with the immobilized antibody. After a short incubation, a conjugate consisting of enzyme-labeled monoclonal antibody directed against a second distinct antigenic site on the D-dimer molecule is pipetted onto the reaction zone of the paper. During this second incubation period, enzyme-labeled antibody reacts with the bound D-dimer, forming an antibody-antigenlabeled antibody sandwich. The unbound labeled antibody is later eluted from the field of view of the Stratus® CS analyzer by applying a substrate wash solution to the center of the reaction zone. By including substrate for the enzyme within the wash solution, initiation of enzyme activity occurs simultaneously with the wash. The enzymatic rate of the bound fraction increases directly with the concentration of D-dimer in the sample. The reaction rate can then be measured by an optical system that monitors the reaction rate via front surface fluorescence. All data analysis functions are performed by the microprocessor within the analyzer.
Here's an analysis of the provided text regarding the Stratus® CS D-Dimer Assay:
1. Table of Acceptance Criteria and Reported Device Performance
The document does not explicitly state "acceptance criteria" in a numerical target for sensitivity, specificity, or NPV. Instead, it presents the device's performance characteristics in a clinical study. We can infer that these reported values were deemed acceptable for market clearance.
| Metric | Reported Device Performance (%) |
|---|---|
| Sensitivity | 94 |
| Specificity | 52 |
| NPV | 95 |
The cutoff used for these performance metrics was 450 ng/mL.
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size: 832 VTE patients were included in the clinical study.
- Data Provenance: Not explicitly stated. The document doesn't specify the country of origin or whether the data was retrospective or prospective.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications
This information is not provided in the given document. The document only mentions a "Clinical Study Summary" without detailing the methodology of ground truth establishment, including the number or qualifications of experts.
4. Adjudication Method for the Test Set
This information is not provided in the given document.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done
This information is not provided in the given document. The study described focuses on the standalone performance of the device rather than a comparative effectiveness study with human readers, with or without AI assistance.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
Yes. The reported performance characteristics (sensitivity, specificity, NPV) are for the Stratus® CS D-Dimer Assay as a standalone diagnostic test. The description of the device's operation (solid phase Radial Partition Immunoassay (RPIA) technology, optical system, microprocessor for data analysis) indicates it's an automated process without direct human intervention in the result generation.
7. The Type of Ground Truth Used
The ground truth used was the diagnosis of Venous Thromboembolism (VTE) for patients (DVT or PE). The document implies a clinical reference standard, where patients were definitively diagnosed as having VTE or not, against which the D-dimer assay results were compared. However, the specific method for establishing this clinical diagnosis (e.g., imaging, clinical probability scores) is not detailed.
8. The Sample Size for the Training Set
The document does not provide information on a separate training set. The reported clinical study appears to be the primary study for performance evaluation, and it mentions a single "VTE Patients" sample size of 832. For diagnostic devices like this, calibration and internal validation often happen during development, but a distinct "training set" in the machine learning sense is not explicitly described.
9. How the Ground Truth for the Training Set Was Established
Since no separate training set is explicitly mentioned or detailed, this information is not provided.
§ 864.7320 Fibrinogen/fibrin degradation products assay.
(a)
Identification. A fibrinogen/fibrin degradation products assay is a device used to detect and measure fibrinogen degradation products and fibrin degradation products (protein fragments produced by the enzymatic action of plasmin on fibrinogen and fibrin) as an aid in detecting the presence and degree of intravascular coagulation and fibrinolysis (the dissolution of the fibrin in a blood clot) and in monitoring therapy for disseminated intravascular coagulation (nonlocalized clotting in the blood vessels).(b)
Classification. Class II (performance standards).