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For In Vitro Diagnostic Use.

The Rheonix STI TriPlex™ Assay, as performed on the Rheonix Encompass MDx® Workstation, is an automated DNA extraction and multiplex PCR amplification test system intended for the direct, qualitative detection of DNA from Chlamydia trachomatis (CT), and/or Neisseria gonorrhoeae (NG), and/or Trichomonas vaginalis (TV) in male urine specimens collected with the Rheonix Urine Specimen Collection Kit. The test is indicated to aid in the diagnosis of chlamydial urogenital disease, gonococcal urogenital disease and trichomoniasis in asymptomatic male individuals.

The Rheonix Encompass MDx® Workstation and the Rheonix STT TriPlex™ Assay are comprised of an instrument with associated hardware and accessories, disposable microfluidic CARD cartridges, master mixes and reagent components used to extract, amplify, and detect DNA using end point PCR. In addition, all male urine specimens in this system must be collected using the Rheonix Urine Specimen Collection Kit. The process is fully automated with the user intervention required only for loading and unloading the samples and disposable assay components. The Rheonix Encompass MDx Workstation's software automatically interprets test results which may be called as POS (positive), NEG (negative), or IND (indeterminate) for each of the assay's three targets. In addition, if the instrument encounters an error during the performance of the assay, it will report an ERR code. If either an IND or ERR code results, the same specimen should be reanalyzed for the presence of the target for which the indeterminate or error code occurred. Each assay has a built-in process control that assures that the individual steps of the entire process occurred properly. The user may also include external positive and/or negative controls to monitor the assay performance.

The Rheonix STI TriPlex Assay, performed on the Rheonix Encompass MDx Workstation, is an automated DNA extraction and multiplex PCR amplification test system for the direct, qualitative detection of DNA from Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), and Trichomonas vaginalis (TV) in male urine specimens.

Here's an analysis of the acceptance criteria and the study that proves the device meets them:

1. Table of Acceptance Criteria and Reported Device Performance:

The document describes the clinical performance (sensitivity and specificity) against a Patient Infection Status (PIS) derived from FDA-cleared Nucleic Acid Amplification Tests (NAATs). While explicit "acceptance criteria" are not listed as pass/fail values, the reported performance metrics serve as the demonstration that the device is fit for its intended use. For the purpose of this response, I will list the observed clinical performance as the "reported device performance," which implicitly met the FDA's criteria for substantial equivalence.

2. Sample size used for the test set and the data provenance:

• Test Set Sample Size:
  • CT and NG: 1606 evaluable male subjects.
  • TV: 1585 evaluable male subjects (out of 1586, one excluded due to invalid test result).
• Data Provenance:
  • Country of Origin: United States. Specimens were collected at 8 geographically distinct sites in the US.
  • Retrospective or Prospective: Prospective. The study enrolled both symptomatic and asymptomatic subjects, and one first-catch urine specimen was collected from each subject.

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

The ground truth, referred to as "Patient Infection Status (PIS)," was established by multiple FDA-cleared Nucleic Acid Amplification Tests (NAATs), not individual human experts. The document does not specify the number or qualifications of experts involved in running these comparator NAATs or interpreting their results beyond the described adjudication method. It implies that these were standard laboratory procedures using cleared devices.

4. Adjudication method (e.g. 2+1, 3+1, none) for the test set:

The adjudication method used to establish the Patient Infection Status (PIS) for the test set was a 2+1 method:

• For each target (CT, NG, TV), up to three different FDA cleared NAATs were used.
• If the first two NAATs yielded concordant results (both positive or both negative), the PIS was defined accordingly.
• If the first two NAATs were not concordant, a third "tie-breaker" test was used. The PIS was then determined based on the majority rule (2 out of 3 results being either positive or negative).

5. 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:

This device is an automated in vitro diagnostic (IVD) assay for nucleic acid detection, not an AI-assisted imaging device that involves human "readers." Therefore, an MRMC comparative effectiveness study involving human readers and AI assistance was not applicable and not performed. The device itself provides an automated interpretation (Positive, Negative, Indeterminate, or Error).

6. If a standalone (i.e., algorithm only without human-in-the-loop performance) was done:

Yes, a standalone performance study was done. The entire premise of the clinical performance evaluation (Tables 15-17) is a direct comparison of the Rheonix STI TriPlex Assay's automated results (Positive, Negative) against the established Patient Infection Status (PIS). There is no mention of a human-in-the-loop component for the Rheonix system's result interpretation. The workstation's software automatically interprets test results.

7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):

The ground truth used was molecular diagnostic consensus derived from multiple FDA-cleared Nucleic Acid Amplification Tests (NAATs). This is a common and accepted method for establishing ground truth in diagnostic studies for infectious diseases, as NAATs are highly sensitive and specific.

8. The sample size for the training set:

The document does not explicitly specify a "training set" for the clinical performance evaluation in the context of device clearance. Instead, it describes analytical and clinical performance studies demonstrating the device's capability. For an IVD like this, "training" typically refers to the development and optimization phase using internal validation data rather than a distinct, reported "training set" from a pivotal clinical trial. No sample size for a separate training set is provided in this submission summary.

9. How the ground truth for the training set was established:

As noted above, a distinct "training set" with ground truth established in the same manner as a clinical test set is not typically described for IVD device submissions in this way. The analytical performance characteristics (e.g., Limit of Detection, Inclusivity, Specificity, Interference, Carry-over) are established using contrived samples with known concentrations of target organisms and potential interfering substances, which serve as a form of "ground truth" for ensuring the assay's fundamental analytical capabilities during its development and internal validation. The clinical study then validates these capabilities in real-world patient samples against the PIS.

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