(79 days)
The AmpliVue® GAS Assay is an in vitro diagnostic test for the qualitative detection of Group A 8hemolytic Streptococcus (Streptococcus pyogenes) nucleic acids isolated from throat swab specimens obtained from patients with signs and symptoms of pharyngitis, such as sore throat.
The AmpliVue® GAS Assay is intended for use in hospital, reference or state laboratory settings. The device is not intended for point-of-care use.
The AmpliVue® GAS Assay combines simple processing, an isothermal amplification technology named helicase-dependent amplification (HDA), and a self-contained disposable amplicon device, for the detection of GAS from throat swab specimens obtained from patients with signs and symptoms of pharyngitis, such as sore throat.
Patient specimen on a throat swab is transferred to a Lysis Tube and subjected to heat treatment at 95℃ for 10 minutes. The heat-treated sample is diluted 10-fold in a Dilution Tube, and then transferred to a Reaction Tube. The reaction tube contains a lyophilized mix of HDA reagents including primers specific for the amplification of the DNase B (sdaB) gene sequence. The assay also includes a process control that monitors sample processing, confirms the integrity of the assay reagents and cassette detection, and assays for HDA inhibitors that may be present within a specimen. After completion of the HDA reaction tube is transferred to a cassette for detection with the test result displayed as test and/or control lines in the window of the cassette.
Here's a breakdown of the acceptance criteria and the study that proves the device meets them, based on the provided text:
1. Table of Acceptance Criteria and Reported Device Performance
Acceptance Criteria for Excluding Follow-up Culture for Negative Results (as stated by FDA):
| Criterion | Device Performance (AmpliVue® GAS Assay) | Meets Criteria? |
|---|---|---|
| Overall sensitivity ≥98%, with the lower bound of the 95% CI of ≥93% from ≥ 100 positive specimens | Overall Sensitivity: 98.4% (189/192) | |
| 95% CI: (95.5%-99.5%) | ||
| (189 positive specimens, which is ≥100) | Yes | |
| Overall NPV >99%, with the lower bound of the 95% CI of >97% extrapolated based on 30% prevalence | Overall NPV (at 30% prevalence): 99.3% | |
| Lower bound of 95% CI (at 30% prevalence): 97.9% | Yes | |
| Each testing site demonstrates an NPV of ≥98% and an approximately even distribution of samples is observed among the sites | Lowest site NPV: 98.7% (Site 5) | |
| (Sample distribution appears somewhat even, with sites ranging from 100 to 500 samples) | Yes |
Clinical Performance (Overall All Sites):
| Metric | Reported Performance (95% CI) |
|---|---|
| Sensitivity | 98.4% (95.5%-99.5%) |
| Specificity | 95.0% (93.5%-96.2%) |
2. Sample Size Used for the Test Set and Data Provenance
- Test Set Sample Size: 1191 prospectively collected fresh throat swab specimens.
- Data Provenance: From five distinct geographical sites across the United States. The study was conducted from February to March 2014, making it a prospective study.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications
The document does not explicitly state the number of experts or their specific qualifications (e.g., "radiologist with 10 years of experience") used to establish the ground truth.
The ground truth was established by "Composite Culture," which involved:
- Culturing the swab specimens at the testing sites.
- Culturing the transport fluid at a central location.
- A "specimen was considered positive if culture from either the swab or the transport fluid was positive for Group A ß-hemolytic Streptococcus."
While culture is a standard method, the text does not detail who performed or interpreted these cultures, or their specific expertise.
4. Adjudication Method for the Test Set
The document does not explicitly describe an "adjudication method" in the traditional sense of multiple expert readers reviewing cases.
However, for discordant results (AmpliVue® GAS Assay vs. Composite Culture), additional testing was performed:
- For the 50 specimens that were AmpliVue® GAS Assay positive but Composite Culture negative, "31 of these specimens were positive for GAS when tested with an additional FDA-cleared molecular device, 18 were negative. One specimen was unavailable for discordant testing."
- For the 3 specimens that were AmpliVue® GAS Assay negative but Composite Culture positive, "two were negative when tested with an additional FDA-cleared molecular device."
This "additional FDA-cleared molecular device" acts as a form of secondary assessment for discordant cases, though it's not a human adjudication process.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not performed. This study focuses on the standalone performance of the AmpliVue® GAS Assay against a composite culture ground truth, not on how human readers' performance might improve with or without AI assistance.
6. Standalone Performance (Algorithm Only Without Human-in-the-Loop)
Yes, a standalone performance study was done. The AmpliVue® GAS Assay is an in vitro diagnostic test that provides a qualitative result (positive/negative) based on the detection of nucleic acids. The clinical performance data presented (sensitivity and specificity) represent the performance of the device itself, without human interpretation or intervention in the diagnostic decision once the test is run and visually read. The result is "visually read" from lines on a cassette, which is an output of the algorithm.
7. Type of Ground Truth Used
The ground truth used for the clinical studies was Composite Culture for Group A ß-hemolytic Streptococcus. This method involved:
- Primary culture of throat swab specimens.
- Culture of transport fluid.
- A sample was deemed positive if either culture (swab or transport fluid) was positive.
8. Sample Size for the Training Set
The document does not provide information regarding a "training set" or its sample size. This is typical for a diagnostic assay submission that focuses on clinical validation of a fixed algorithm rather than iterative machine learning model development. The assay uses specific primers and probes for the GAS sdaB gene sequence, which implies a pre-defined molecular design rather than a data-driven training process in the AI/ML sense.
9. How the Ground Truth for the Training Set Was Established
As no training set is described in the context of an AI/ML model, the establishment of ground truth for a training set is not applicable to this submission. The assay's design (primers, probes) would have been developed based on existing biological knowledge of the GAS genome.
§ 866.2680
Streptococcus spp. nucleic acid-based assay.(a)
Identification. AStreptococcus spp. nucleic acid-based assay is a qualitative in vitro diagnostic device intended to simultaneously detect and identify variousStreptococcus spp. nucleic acids extracted directly from clinical specimens. The device detects specific nucleic acid sequences for organism identification. The identification aids in the diagnosis of diseases caused by bacteria belonging to the genusStreptococcus and provides epidemiological information on these diseases. Pathogenic streptococci are associated with infections, such as sore throat, impetigo (an infection characterized by small pustules on the skin), urinary tract infections, rheumatic fever, and kidney disease.(b)
Classification. Class II (special controls). The special controls for this device are:(1) Premarket notification submissions must include detailed device description documentation, including the device components, ancillary reagents required but not provided, and a detailed explanation of the methodology including primer/probe sequence, design, and rationale for sequence selection.
(2) Premarket notification submissions must include detailed documentation from the following analytical and clinical performance studies: Analytical sensitivity (Limit of Detection), reactivity, inclusivity, precision, reproducibility, interference, cross reactivity, carry-over, and cross contamination.
(3) Premarket notification submissions must include detailed documentation from a clinical study. The study, performed on a study population consistent with the intended use population, must compare the device performance to results obtained from well-accepted reference methods.
(4) Premarket notification submissions must include detailed documentation for device software, including, but not limited to, software applications and hardware-based devices that incorporate software.
(5) Premarket notification submissions must include database implementation methodology, construction parameters, and quality assurance protocols, as appropriate.
(6) The device labeling must include limitations regarding the need for culture confirmation of negative specimens, as appropriate.
(7) A detailed explanation of the interpretation of results and acceptance criteria must be included in the device's 21 CFR 809.10(b)(9) compliant labeling.
(8) Premarket notification submissions must include details on an end user device training program that will be offered while marketing the device, as appropriate.