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Venous photoplethysmography and bi-directional Doppler for venous and arterial vonous protoproxity and for screening for the absence of deep venous thrombosis (DVT) in the lower limb.

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This 510(k) submission describes the expansion of indications for use for the Rheo Dopplex® II device to include "screening for the absence of deep venous thrombosis (DVT) in the lower limb." The provided documents contain a summary of the clinical study conducted to support this new indication.

Here's an analysis of the acceptance criteria and study information:

1. Table of Acceptance Criteria and Reported Device Performance

The submission does not explicitly state specific acceptance criteria for sensitivity, specificity, and predictive values. However, it reports the device performance in these metrics. Without explicitly stated acceptance criteria, it's impossible to determine if the reported device performance met predefined targets. The reported values are presented as descriptive statistics from the study.

Note: The low specificity and positive predictive value (PPV) might be a concern in some contexts, but without explicit acceptance criteria, it's difficult to comment on whether these values were considered acceptable by the regulatory body for the intended use of screening for the absence of DVT. High sensitivity and NPV are often prioritized for screening devices where missing a condition could have severe consequences.

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

The provided text does not specify the sample size used for the test set in the clinical studies.

The data provenance is also not explicitly stated (e.g., country of origin). The studies are described as "Clinical data to support this expanded Indications for Use," implying they were conducted to gather evidence for this specific submission. It is not mentioned whether the studies were retrospective or prospective.

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

The document states that the clinical data included "studies comparing the Rheo Dopplex® II with duplex imaging and venography for the confirmation of the absence of a DVT in the lower limb."

• Ground Truth Modalities: Duplex imaging and venography are mentioned as the reference standards for DVT confirmation.
• Number of Experts: The number of experts involved in interpreting the duplex imaging and venography results, or in establishing the ground truth, is not specified.
• Qualifications of Experts: The qualifications of any experts involved are not specified.

4. Adjudication Method for the Test Set

The adjudication method for establishing the ground truth from duplex imaging and venography is not described in the provided text.

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

There is no mention of a multi-reader multi-case (MRMC) comparative effectiveness study comparing human readers with and without AI assistance. The Rheo Dopplex® II is a device for physiological measurement (venous photoplethysmography and bi-directional Doppler), not an AI-powered diagnostic imaging system that aids human readers in image interpretation. Therefore, this type of study would not be applicable.

6. Standalone (Algorithm Only Without Human-in-the-Loop Performance) Study

The performance metrics (Sensitivity, Specificity, NPV, PPV) described are for the standalone performance of the Rheo Dopplex® II device. The clinical data directly compares the device's output to established reference standards (duplex imaging and venography) for DVT confirmation. There is no indication of a human-in-the-loop component in how these performance metrics were derived.

7. Type of Ground Truth Used

The ground truth used was established by referencing duplex imaging and venography. These are established clinical diagnostic methods used for confirming the presence or absence of deep venous thrombosis.

8. Sample Size for the Training Set

The document does not mention a "training set". Given that the Rheo Dopplex® II is a physiological measurement device and not described as an AI/ML-based system, the concept of a separate "training set" and "test set" in the context of machine learning model development is likely not applicable here. The "clinical data" described would typically refer to data used for validation/testing of the device's performance against a reference standard.

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

As stated above, a "training set" is not referenced for this device. The ground truth for the clinical studies (validation/testing) was established using duplex imaging and venography.

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