FDA 510(k) Search - By Innolitics (SaMD and AI Experts)

The Aptima Combo 2 Assay is a target amplification nucleic acid probe test that utilizes target capture for the in vitro qualitative detection and differentiation of ribosomal RNA (rRNA) from Chlamydia trachomatis (CT) and/or Neisseria gonorrhoeae (GC) to aid in the diagnosis of chlamydial and/or gonococcal disease using the Panther System as specified. On the Panther System, the assay may be used to test the following specimens from symptomatic and asymptomatic individuals: clinician-collected endocervical, PreservCyt® Solution liquid Pap specimens, vaginal, throat, rectal, and male urethral swab specimens; patient-collected vaginal swab specimens1, and female and male urine specimens.

The Aptima Combo 20 Assay is a target amplification nucleic acid probe test that utilizes target capture for the in vitro qualitative detection and differentiation of ribosomal RNA (rRNA) from Chlamydia trachomatis (CT) and/or Neisseria gonorrhoeae (GC) to aid in the diagnosis of chlamydial and/or gonococcal urogenital disease using the Tigris® DTS® Automated Analyzer or semi-automated instrumentation as specified. The assay may be used to test the following specimens from symptomatic individuals: clinician-collected endocervical, vaginal and male urethral swab specimens; and female and male urine specimens. The assay may be used to test the following specimens from asymptomatic individuals: clinician-collected endocervical, vaginal and male urethral swab specimens; patient-collected vaginal swab specimens'; and female and male urine specimens. The assay is also intended for use with the testing of gynecological specimens, from both symptomatic and asymptomatic patients, collected in the PreservCyt® Solution.

Device Description

The Aptima Combo 2 Assay combines the technologies of target capture, TMA, and DKA. Specimens are collected and transferred into their respective specimen transport tubes. The transport solutions in these tubes release the rRNA targets and protect them from degradation during storage. When the Aptima Combo 2 Assay is performed in the laboratory, the target rRNA molecules are isolated from specimens by use of capture oligomers via target capture that utilizes magnetic microparticles. The capture oligomers contain sequences complementary to specific regions of the target molecules as well as a string of deoxyadenosine residues. A separate capture oligomer is used for each target. During the hybridization step, the sequence specific regions of the capture oligomers bind to specific regions of the target molecules. The capture oligomer:target complex is then captured out of solution by decreasing the temperature of the reaction to room temperature. This temperature reduction allows hybridization to occur between the deoxyadenosine region on the capture oligomer and the poly-deoxythymidine molecules that are covalently attached to the magnetic particles. The microparticles, including the captured target molecules bound to them, are pulled to the side of the reaction vessel using magnets and the supernatant is aspirated. The particles are washed to remove residual specimen matrix that may contain amplification reaction inhibitors. After the target capture steps are completed, the specimens are ready for amplification.

Target amplification assays are based on the ability of complementary oligonucleotide primers to specifically anneal and allow enzymatic amplification of the target nucleic acid strands. The Aptima Combo 2 Assay replicates a specific region of the 23S rRNA from CT and a specific region of the 16S rRNA from GC via DNA intermediates. A unique set of primers is used for each target molecule. Detection of the rRNA amplification product sequences (amplicon) is achieved using nucleic acid hybridization. Single-stranded nucleic acid chemiluminescent probes, which are complementary to a region of each target amplicon, are labeled with different acridinium ester molecules. The updated version of the Aptima Combo 2 assay incorporates a second CT probe, complementary to a unique region of the existing CT amplicon. This tandem probe provides detection coverage for the variant strains of C. trachomatis that emerged in 2019. The labeled probes combine with amplicon to form stable hybrids. The Selection Reagent differentiates hybridized from unhybridized probe, eliminating the generation of signal from unhybridized probe. During the detection step, light emitted from the labeled hybrids is measured as photon signals in a luminometer, and are reported as Relative Light Units (RLU). In DKA, differences in the kinetic profiles of the CT and GC labeled probes allow for the differentiation of signal; kinetic profiles are derived from measurements of photon output during the detection read time. The chemiluminescent detection for CT signal has very rapid kinetics and has the "flasher" kinetic type. The chemiluminescent detection reaction for GC signal is relatively slower and has the "glower" kinetic type. Assay results are determined by a cut-off based on the total RLU and the kinetic curve type.

AI/ML Overview

The provided text describes a 510(k) premarket notification for a modified diagnostic device, the Aptima Combo 2 Assay, used for detecting Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC). The modification involves a change in the Probe reagent to improve detection of emerging CT variants.

Here's an analysis of the acceptance criteria and the study that proves the device meets them, based on the provided document:

1. Table of Acceptance Criteria and Reported Device Performance

The FDA 510(k) submission process for in vitro diagnostic devices focuses on demonstrating substantial equivalence to a legally marketed predicate device. For modifications to an existing cleared device, the key acceptance criteria revolve around showing that the changes do not negatively impact the assay's performance, safety, and effectiveness, and specifically address the reason for the modification (improved CT variant detection).

While explicit enumerated "acceptance criteria" with numerical thresholds are not presented in a table format as might be seen for a new device, the document implies the following performance criteria were met:

Performance Characteristic	Acceptance Criteria (Implied)	Reported Device Performance (Updated AC2 Assay)
Limit of Detection (LoD) for FI-nvCT	LoD for the Finnish variant of Chlamydia trachomatis (FI-nvCT) should be within acceptable limits (typically very low concentration).	Determined to be less than one IFU per assay in urine, ThinPrep, and simulated swab matrix specimens on both Panther and Tigris systems. Detection capabilities confirmed across multiple CT variants. This indicates high sensitivity for the targeted variants.
Clinical Comparability - CT	High positive and negative percent agreement with the current (predicate) AC2 assay for CT detection. Data should support that the updated assay performs similarly to the predicate on clinical samples.	Positive Percent Agreement (PPA): 100% (95% C.I.: 92.7% - 100%)
Negative Percent Agreement (NPA): 98.9% (95% C.I.: 96.9% - 99.6%)
Overall agreement was >99.0% for CT. This demonstrates strong concordance with the predicate device.
Clinical Comparability - GC	High positive and negative percent agreement with the current (predicate) AC2 assay for GC detection. Data should support that the updated assay performs similarly to the predicate on clinical samples.	Positive Percent Agreement (PPA): 100% (95% C.I.: 92.4% - 100%)
Negative Percent Agreement (NPA): 99.6% (95% C.I.: 98.0% - 99.9%)
Overall agreement was >99.0% for GC. This demonstrates strong concordance with the predicate device, also showing no negative impact on GC detection.
Clinical Panel Agreement (CT/GC)	High agreement (100% or very close) to expected panel results for both wild type CT, FI-nvCT, and GC across various concentrations. Consistency across instruments, lots, operators, days, and runs.	100% (97.6-100%) total CT and GC agreement to the expected panel result for the updated AC2 assay.
For the current AC2 assay, 100% agreement except for the moderate (0.2 IFU/mL) FI-nvCT only panel (98.2% CT agreement, 99.1% GC agreement). This indicates the updated assay improves detection of the FI-nvCT variant while maintaining performance for other targets. Variability was comparable.
Microorganism Cross-Reactivity and Microbial Interference	No significant impact on detection capabilities or analytical specificity from a panel of common microorganisms. No false positives or interference should occur.	None of the 86 microorganisms tested were found to have an impact on the detection capabilities or analytical specificity of the updated version of the AC2 assay. This demonstrates high specificity and robustness against common interfering substances/microorganisms.
Overall Risk Profile	No new hazards introduced, and the overall residual risk does not increase compared to currently marketed products. Risks should be reduced as far as possible and meet pre-defined acceptability criteria.	Based on risk analysis and verification activities, all risks are reduced as far as possible and meet pre-defined acceptability criteria. No hazards fell within "Undesirable" or "Unacceptable" residual risk regions. Device modifications do not introduce any new hazards or increase the overall residual risk.

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

Limit of Detection (LoD) Study:
- Sample Size: 30 replicates of each dilution were tested for each specimen type (urine, ThinPrep, simulated swab matrix). This was done with 3 reagent lots on both Panther and Tigris systems.
- Total replicates: 30 (replicates/dilution) * 3 (specimen types) * 3 (lots) * 2 (systems) = 540 replicates per target organism (CT/GC).
- Data Provenance: In vitro transcripts diluted in negative urine specimens, negative ThinPrep specimens, and simulated swab matrix specimens. This is laboratory-derived analytical data, not directly stated to be from a particular country. It is essentially prospective in nature for validating the new formulation.
Clinical Comparability Study:
- Sample Size: Not explicitly stated as a total count, but implied by the comparison tables below Table 4 and Table 5.
  - CT: 49 CT positive, 273 CT negative, 3 discordant (updated positive, current negative). Total: 325 remnant samples.
  - GC: 47 GC positive, 275 GC negative, 1 discordant (updated positive, current negative). Total: 323 remnant samples.
- Data Provenance: Remnant swab specimens collected from patients undergoing CT and/or GC screening. The origin country is not specified, but it's retrospective use of existing clinical samples.
CT/GC Clinical Panel Agreement Study:
- Sample Size: 20 prepared CT/GC clinical panels. Each panel was tested in triplicate, in two runs per day, on three Panther systems, by two operators, using three lots of reagents over seven days.
- Total tests: 20 (panels) * 3 (replicates) * 2 (runs/day) * 3 (systems) * 2 (operators) * 3 (lots) * 7 (days) = This calculation seems off and yields a very large number. More simply, if each panel was tested in triplicate across the stated conditions, the total number of data points specifically for these panels would be substantial. The document states "Each of the 20 panels were tested in triplicate...over seven days", implying multiple runs under varying conditions, leading to hundreds of data points (e.g., 20 panels * 3 replicates * 2 runs * 3 systems * 3 lots * 2 operators * 7 days if all combinations were run, which is impractical; more likely "across" these variables). Let's interpret "in triplicate...over seven days" as at least 3 runs per panel across variable conditions for a total of 60 tests (20 panels * 3 replicates) per condition (e.g., per system/lot/operator combination). The key is "The results show 100%...total CT and GC agreement to the expected panel result for the updated AC2 assay."
- Data Provenance: Prepared clinical panels containing known concentrations of wild type CT, FI-nvCT, and GC in urine specimens. This is an expertly constructed analytical study, effectively prospective in its execution for validation.

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

The document does not mention the use of human experts (e.g., radiologists) for establishing ground truth for a test set. This is a molecular diagnostic assay, not an imaging device. Ground truth for these studies is typically established by:

Analytical studies: Known concentrations of purified nucleic acids (e.g., in vitro transcripts) or spiked microorganisms.
Clinical comparability: Agreement with a legally marketed predicate device (the "current" AC2 assay) on remnant clinical samples. The predicate device itself was cleared based on its own performance studies.
Clinical panels: Known concentrations of target organisms in simulated or real matrices.

Therefore, the concept of "experts" in the context of ground truth establishment for this specific device would relate to the scientific team involved in designing the analytical panels and interpreting the molecular results, rather than clinical experts adjudicating cases.

4. Adjudication Method for the Test Set

Not applicable in the typical sense for this type of device. There's no "adjudication" of images or clinical cases by multiple readers. The output of the device is a qualitative "positive" or "negative" result based on Relative Light Units (RLU) and kinetic curve type. Equivalence is determined by statistical agreement (percent agreement) between the test device and the predicate or expected panel results.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done

No. An MRMC study is relevant for imaging devices where human readers interpret medical images, often with and without AI assistance, to assess diagnostic performance. This document concerns a molecular diagnostic assay where a laboratory instrument provides a qualitative result. There is no human "reading" of the assay outcome in the same way an image is read.

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done

Yes, implicitly. The performance data presented (LoD, clinical comparability, clinical panel agreement, cross-reactivity) are all "standalone" in the sense that they demonstrate the analytical and clinical performance of the assay system itself (reagent + instrument) without any direct human interpretation of raw data (beyond standard laboratory procedures for operating the instrument and interpreting its final qualitative output, which is not "in-the-loop" AI assistance). The device is intended to provide a diagnostic result directly.

7. The Type of Ground Truth Used

Analytical Studies (LoD, Cross-Reactivity, Microbial Interference): "Spiked" or "known concentration" ground truth. For example, FI-nvCT in vitro transcripts at varying known concentrations, or panels of known microorganisms.
Clinical Comparability: The results from the predicate device (current AC2 assay) on remnant clinical samples served as the de-facto ground truth for evaluating equivalence. While not "absolute" ground truth (like pathology), it's the standard for substantial equivalence in device modifications.
Clinical Panel Agreement: Expected panel result based on known concentrations of spiked organisms. This is a form of engineered, highly controlled ground truth.

8. The Sample Size for the Training Set

The document does not directly disclose the sample size for the training set. This is a common characteristic of medical device submissions, as the focus is on validation (test set performance) rather than the proprietary details of model training (if applicable to this type of assay, though molecular assays often rely on established biochemical principles rather than "training" in the machine learning sense). The development of the reformulated probe reagent would have involved laboratory optimization and characterization experiments, which are analogous to a "training" phase.

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

Since this is a molecular diagnostic assay and not an AI/ML product requiring extensive "training" data, the concept of "ground truth for the training set" isn't directly applicable in the same way. The development process for the reformulated probe would have involved:

Understanding the genetic variants: Identifying the specific mutations in the C. trachomatis variants (e.g., FI-nvCT) that caused detection issues with the previous probe.
Rational design: Designing new probe sequences that would bind effectively to both the original target and the new variants.
Iterative testing and optimization: Extensive laboratory testing of various probe formulations using cultured organisms, synthetic nucleic acids, and potentially some clinical samples to ensure desired performance (sensitivity, specificity, variant detection) during the development phase. This iterative process, guided by known target sequences and laboratory results, serves as the "ground truth" for optimizing the assay components.

In summary, the submission demonstrates that the modified Aptima Combo 2 Assay maintains or improves its performance compared to the predicate device, particularly in its ability to detect emerging CT variants, without compromising its overall accuracy or introducing new risks. The studies are analytical and comparative, appropriate for a molecular diagnostic device modification rather than an imaging AI solution.

Summary

Regulation Number and Section

§ 866.3393 Device to detect nucleic acids from non-viral microorganism(s) causing sexually transmitted infections and associated resistance marker(s).

(a)
Identification. A device to detect nucleic acids from non-viral microorganism(s) causing sexually transmitted infections and associated resistance marker(s) is an in vitro diagnostic device intended for the detection and identification of nucleic acids from non-viral microorganism(s) and their associated resistance markers in clinical specimens collected from patients suspected of sexually transmitted infections. The device is intended to aid in the diagnosis of non-viral sexually transmitted infections in conjunction with other clinical and laboratory data. These devices do not provide confirmation of antibiotic susceptibility since mechanisms of resistance may exist that are not detected by the device.(b)
Classification. Class II (special controls). The special controls for this device are:(1) The intended use for the labeling required under § 809.10 of this chapter must include a detailed description of targets the device detects, the results provided to the user, the clinical indications appropriate for test use, and the specific population(s) for which the device is intended.
(2) Any sample collection device used must be FDA-cleared, -approved, or -classified as 510(k) exempt (standalone or as part of a test system) for the collection of specimen types claimed by this device; alternatively, the sample collection device must be cleared in a premarket submission as a part of this device.
(3) The labeling required under § 809.10(b) of this chapter must include:
(i) A detailed device description, including reagents, instruments, ancillary materials, all control elements, and a detailed explanation of the methodology, including all pre-analytical methods for processing of specimens;
(ii) Detailed discussion of the performance characteristics of the device for all claimed specimen types based on analytical studies, including Limit of Detection, inclusivity, cross-reactivity, interfering substances, competitive inhibition, carryover/cross contamination, specimen stability, within lab precision, and reproducibility, as appropriate;
(iii) Detailed descriptions of the test procedure, the interpretation of test results for clinical specimens, and acceptance criteria for any quality control testing;
(iv) Limiting statements indicating that:
(A) A negative test result does not preclude the possibility of infection;
(B) The test results should be interpreted in conjunction with other clinical and laboratory data available to the clinician;
(C) Reliable results are dependent on adequate specimen collection, transport, storage, and processing. Failure to observe proper procedures in any one of these steps can lead to incorrect results; and
(D) If appropriate (
e.g., recommended by the Centers for Disease Control and Prevention, by current well-accepted clinical guidelines, or by published peer reviewed research), that the clinical performance is inferior in a specific clinical subpopulation or for a specific claimed specimen type; and(v) If the device is intended to detect antimicrobial resistance markers, limiting statements, as appropriate, indicating that:
(A) Negative results for claimed resistance markers do not indicate susceptibility of detected microorganisms, as resistance markers not measured by the assay or other potential mechanisms of antibiotic resistance may be present;
(B) Detection of resistance markers cannot be definitively linked to specific microorganisms and the source of a detected resistance marker may be an organism not detected by the assay, including colonizing flora;
(C) Detection of antibiotic resistance markers may not correlate with phenotypic gene expression; and
(D) Therapeutic failure or success cannot be determined based on the assay results, since nucleic acid may persist following appropriate antimicrobial therapy.
(4) Design verification and validation must include:
(i) Detailed device description documentation, including methodology from obtaining sample to result, design of primer/probe sequences, rationale for target sequence selection, and computational path from collected raw data to reported result (
e.g., how collected raw signals are converted into a reported result).(ii) Detailed documentation of analytical studies, including, Limit of Detection, inclusivity, cross-reactivity, microbial interference, interfering substances, competitive inhibition, carryover/cross contamination, specimen stability, within lab precision, and reproducibility, as appropriate.
(iii) Detailed documentation and performance results from a clinical study that includes prospective (sequential) samples for each claimed specimen type and, when determined to be appropriate by FDA, additional characterized clinical samples. The study must be performed on a study population consistent with the intended use population and compare the device performance to results obtained from FDA accepted comparator methods. Documentation from the clinical studies must include the clinical study protocol (including a predefined statistical analysis plan) study report, testing results, and results of all statistical analyses.
(iv) A detailed description of the impact of any software, including software applications and hardware-based devices that incorporate software, on the device's functions.