Search Results

The STA® - Liatest® D-Di kit is an immuno-turbidimetric assay for the quantitative determination of D-dimer in venous plasma (in 3.2% sodium citrate) for use on STA-R®, STA Compact® and STA Satellite® analyzers by professional laboratory personnel. The STA® - Liates® D-Di is intended for use in conjunction with a clinical pretest probability (PTP) assessment model to exclude pulmonary embolism (PE) and as an aid in the diagnosis of deep venous thrombosis (DVT) in outpatients suspected of PE or DVT.

STA® - Liatest® D-Di kit contains: 6 x 5-ml vials of ready-for-use Tris buffer and 6 x 6-ml vials of a suspension of microlatex particles coated with two different mouse monoclonal anti-human D-dimer antibodies (8D2 and 2.1.16) stabilized with bovine albumin.

The test principle is based on the change in turbidity of a microparticle suspension that is measured by photometry. A suspension of latex microparticles, coated by covalent bonding with monoclonal antibodies specific for D-dimer is mixed with the test plasma for which the D-dimer level is to be assayed. An antigen-antibody reaction takes place, leading to an agglutination of the latex microparticles which causes an increase in turbidity of the reaction medium. This increase in turbidity is reflected by an increase in absorbance, the latter being measured photometrically. The increase in absorbance is a function of the D-dimer level present in the test sample.

Here's a breakdown of the acceptance criteria and the study details for the STA® - Liatest® D-Di device, based on the provided document:

Acceptance Criteria and Reported Device Performance

The acceptance criteria for the STA® - Liatest® D-Di device are implicitly tied to its ability to
safely rule out Pulmonary Embolism (PE) in patients with low or moderate pretest probability (PTP).
The key performance metric for exclusion of PE is the Negative Predictive Value (NPV).

Study Details

1. Sample Size used for the test set and the data provenance:

   • Total Test Set Sample Size: 1130 samples of patients with a low or moderate PTP.
     • Prospective Study Population: 1060 samples.
     • US Banked Samples (retrospective): 70 samples.
   • Data Provenance: The study involved multiple centers across the United States, Europe, and Canada for the prospective data. The banked samples were from the US. The overall study is a mix of prospective and retrospective data.

2. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
   The document does not specify the number or qualifications of experts used to establish the ground truth. The ground truth was established through a combination of imaging procedures for positive PE cases and a 3-month follow-up for negative PE cases.

3. Adjudication method for the test set:
   The document does not explicitly describe a specific adjudication method for the test set results. Diagnosis of PE was based on imaging or clinical follow-up. For patients with suspected PE, those with positive D-dimer results were considered for an imaging procedure. Patients with negative D-dimer results were considered not to have PE and were assigned to a three-month follow-up. This implies a diagnostic pathway rather than a direct adjudication process by a panel of experts on each case.

4. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:
   No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done. This device is an in-vitro diagnostic assay (D-dimer test) and not an AI-assisted diagnostic imaging device that would typically involve human readers. Therefore, the concept of human readers improving with or without AI assistance is not applicable here.

5. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:
   Yes, a standalone performance study was done for the STA® - Liatest® D-Di device. The reported sensitivity, specificity, NPV, and PPV are for the device's performance alone in determining D-dimer levels and, in conjunction with PTP, for PE exclusion. While the device is "intended for use in conjunction with a clinical pretest probability (PTP) assessment model," the performance metrics presented specifically reflect the diagnostic accuracy of the D-dimer assay within that pathway.

6. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):
   The ground truth was established through a combination of imaging procedures (for positive PE cases) and outcomes data (3-month follow-up for negative PE cases).

7. The sample size for the training set:
   The document does not specify a separate training set sample size. The study focuses on demonstrating the performance of the device in a clinical setting based on a defined test set. For an in-vitro diagnostic like this, the "training" (e.g., assay optimization, establishing parameters) is typically internal to the manufacturer's development process and not part of the clinical performance study reported for regulatory submission in the same way an AI model's training set would be.

8. How the ground truth for the training set was established:
   As no separate "training set" is described in the context of this regulatory submission, how its ground truth was established is not provided. The ground truth for the test set was established as described in point 6.

Ask a specific question about this device