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The cobas liat CT/NG nucleic acid test is an automated, qualitative in vitro nucleic acid diagnostic test that utilizes realtime polymerase chain reaction (PCR) for the direction of Chlamydia (CT) and Neisseria gonorthoeae (NG) nucleic acid in male urine and vaginal swabs, all in cobas PCR Media (Roche Molecular Systems, Inc.).

This test is intended as an aid in the diagnosis of urogenital infections in both symptomatic individuals.

The test is performed on the cobas® liat analyzer which automates and integrates sample purification, nucleic acid amplification, and detection of the target sequence in biological samples using real-time PCR assays. The assay targets both the Cryptic plasmid and 23S rRNA of Chlamydia trachomatis and the pivNG and NGR9 of Neisseria gonorrhoeae. An Internal Control (IC) is also included. The IC is present to control for adequate processing of the target bacteria through steps of sample purification, nucleic acid amplification, and to monitor the presence of inhibitors in the PCR processes.

Here's a summary of the acceptance criteria and study details for the cobas® liat CT/NG nucleic acid test, based on the provided document:

1. Table of Acceptance Criteria and Reported Device Performance

The document primarily provides performance metrics rather than explicitly stated acceptance criteria with numerical targets. However, based on the demonstrated performance and the context of a 510(k) submission, the implicit acceptance criteria would be high sensitivity and specificity, indicating reliable detection of CT and NG infections.

2. Sample Size and Data Provenance

• Clinical Study Test Set (Prospectively collected):
  • Total Evaluated Subjects: 4780 (2304 males, 2476 females)
  • Male Urine Specimens: 2302 (from 2302 male subjects)
  • Vaginal Swabs: 2476 (1240 clinician-collected, 1236 self-collected from 2476 female subjects)
  • Data Provenance: Multi-site, prospective study collected at 13 geographically diverse clinical sites across the US.
• Clinical Study Test Set (Archived Specimens - Supplementation):
  • Archived Male Urine Specimens: 163
  • Archived Vaginal Swabs: 90
  • Data Provenance: Prospectively collected samples from a prior clinical trial (K173887).
• Reproducibility Study Test Set: Total 1618 tests (811 vaginal, 807 urine) across 3 external sites. Each panel member tested in triplicate. Low positive (1-2x LoD), moderate positive (3-5x LoD), and negative panel members used.
• Supplemental Precision Study (for CT in urine): 810 evaluable tests on urine panel members (negative, 1x-2x LoD, 3x-5x LoD).

3. Number of Experts and Qualifications for Ground Truth

The ground truth for the clinical study was established using a Patient Infected Status (PIS) or Composite Comparator Algorithm (CCA), which relied on a combination of three FDA-cleared NAATs (NAAT1, NAAT2, and NAAT3). The document does not specify the number of human experts used to establish the ground truth or their qualifications for the clinical study. The "ground truth" was algorithmically derived from the results of the comparator NAATs.

4. Adjudication Method for the Test Set

The adjudication method for the clinical study ground truth (PIS/CCA) followed a rule-based algorithm:

• If NAAT1 and NAAT2 were concordant, that result was the final PIS/CCA.
• If NAAT1 and NAAT2 were discordant, NAAT3 was performed as the tiebreaker.

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

• No, an MRMC comparative effectiveness study was not done. This study assesses the performance of a diagnostic test (the cobas® liat CT/NG nucleic acid test), which is an automated, qualitative in vitro nucleic acid diagnostic test. It replaced human assessment with an automated process, and the comparison was against a PIS/CCA derived from other reference NAATs, not human readers with and without AI assistance. Therefore, there is no effect size for human readers improving with AI.

6. Standalone (Algorithm Only) Performance

• Yes, a standalone (algorithm only) performance study was done. The entire clinical performance evaluation, reproducibility studies, and analytical studies assess the performance of the cobas® liat CT/NG nucleic acid test itself, which is an automated device performing real-time PCR. It is designed to operate without human intervention beyond sample loading and results interpretation from the automated output.

7. Type of Ground Truth Used

• Clinical Study: Patient Infected Status (PIS) or Composite Comparator Algorithm (CCA) derived from the concordant results of FDA-cleared Nucleic Acid Amplification Tests (NAATs).
• Analytical Studies (LoD, Inclusivity, Specificity, Interference): Known concentrations of specific strains or culture subtypes of bacteria/viruses, spiked into negative clinical specimens.

8. Sample Size for the Training Set

The document does not explicitly describe a separate "training set" for an AI/ML model for the cobas® liat CT/NG nucleic acid test. As a nucleic acid diagnostic test (real-time PCR), it operates based on established biochemical principles and does not typically involve machine learning training in the same way an imaging AI algorithm would. All the data presented is for validation and performance evaluation.

9. How Ground Truth for the Training Set Was Established

Since there is no explicitly mentioned "training set" for an AI/ML model in this context, the method for establishing ground truth for such a set is not applicable or described. The clinical performance is evaluated against a PIS/CCA derived from other NAATs, and analytical performance is against known concentrations.

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