(28 days)
The Xpert® SA Nasal Complete test performed on the GeneXpert® Instrument Systems is a qualitative in vitro diagnostic test designed for detection of Staphylococcus aureus (SA) and methicillin-resistant Staphylococcus aureus (MRSA) from nasal swabs in patients at risk for nasal colonization. The test utilizes automated real-time polymerase chain reaction (PCR) to detect MRSA/SA DNA. The Xpert SA Nasal Complete test is intended to aid in the prevention and control of MRSA/SA infections in healthcare settings. The Xpert SA Nasal Complete test is not intended to diagnose, guide or monitor treatment for MRSA/SA infections, or provide results of susceptibility to methicillin. A negative result does not preclude MRSA/SA nasal colonization. Concomitant cultures are necessary to recover organisms for epidemiological typing or for further susceptibility testing.
The Xpert SA Nasal Complete test is an automated in vitro diagnostic DNA test for the qualitative, simultaneous detection of Staphylococcus aureus (SA) and methicillin-resistant Staphylococcus aureus (MRSA) directly from nasal swabs. The specimen is collected on a double swab, one of which is placed in a tube containing elution reagent. Following brief vortexing, the eluted material is transferred to different, uniquely-labeled chamber of the disposable fluidic cartridge (the Xpert SA Nasal Complete cartridge). The user initiates a test from the user interface of the GeneXpert® Instrument Systems and places the cartridge with sample into the GeneXpert® Instrument System platform, which performs hands-off real-time, multiplex polymerase chain reaction (PCR) for detection of S. aureus (including MRSA) DNA.
In the GeneXpert® Instrument Systems (comprised of the GeneXpert® Dx Systems, GeneXpert® System with Touchscreen, and GeneXpert® Infinity Systems), sample preparation, amplification, and real-time detection are all fully-automated and completely integrated. The platform requires the use of single-use disposable cartridges that hold the PCR reagents and host the PCR process. Because the cartridges are self-contained, cross-contamination between samples is minimized.
Depending on the specific instrument, the GeneXpert® Instrument Systems may contain 1–80 modules, each of which are randomly accessible and capable of performing separate sample preparation and real-time PCR tests. Each module contains a syringe drive for dispensing fluids (i.e., the syringe drive activates the plunger that works in concert with the rotary valve in the cartridge to move fluids between chambers), an ultrasonic horn for lysing cells or spores, and a proprietary I-CORE thermocycler for performing real-time PCR and detection.
The Xpert SA Nasal Complete test kit includes reagents for the simultaneous detection of SA and MRSA targets. The primers and probes provided in the Xpert SA Nasal Complete test kit detects nucleic acid sequences of the staphylococcal protein A (spa), the gene for methicillin/oxacillin resistance (mecA), and staphylococcal cassette chromosome (SCCmec) inserted in the SA chromosomal attB site.
The Xpert SA Nasal Complete cartridge includes a sample processing control (SPC) to control for adequate processing of the target bacteria and to monitor the presence of inhibitor(s) in the PCR assay. The Probe Check Control (PCC) verifies reagent rehydration, PCR tube filling in the cartridge, probe integrity, and dve stability.
The Xpert SA Nasal Complete test performed on the GeneXpert® Instrument Systems provides results in approximately 65 minutes.
Each instrument in the GeneXpert® Instrument family is equipped with a Windows OS-based personal computer that is preloaded with software applications for running the tests and viewing the results, as described in Table 1.
Acceptance Criteria and Study Details for Xpert SA Nasal Complete (K243070)
This submission (K243070) seeks to modify the existing Xpert SA Nasal Complete device (K100822) to include the GeneXpert® Infinity Systems instruments in its compatible instrument family. The study described focuses on demonstrating equivalent performance on the new instrument systems.
1. Table of Acceptance Criteria and Reported Device Performance
The provided document doesn't explicitly state quantitative acceptance criteria for clinical performance (e.g., sensitivity, specificity) for this specific 510(k) submission (K243070). This is likely because the core assay and its clinical performance were extensively validated and accepted during the original clearance of K100822, and this submission focuses on adding new compatible instruments while demonstrating equivalent performance.
However, based on the studies conducted, the implicit acceptance criteria relate to demonstrating equivalent performance on the new GeneXpert Infinity Systems compared to the predicate device run on previously cleared GeneXpert systems.
| Acceptance Criteria (Implied) | Reported Device Performance |
|---|---|
| Prepared cartridge hold time: Maximum acceptable hold time verified. | 4 hours (maximum acceptable hold time verified). |
| Functional testing: 100% agreement of reportable results for both contrived positive (MRSA) and negative samples. | 100% agreement of reportable results. |
| Functional testing: No statistically significant differences in Ct values observed between assay runs on GeneXpert Dx Systems and GeneXpert Infinity Systems. | No statistically significant differences in Ct values observed. |
| Overall Performance: Performance claims of the Xpert SA Nasal Complete test not impacted by modifications. | Assessment determined performance claims were not impacted. |
2. Sample Size Used for the Test Set and Data Provenance
The document describes two types of studies impacting the acceptance criteria:
-
Prepared Cartridge Hold Time Study:
- Sample Size: Not explicitly stated. The study involved verifying a maximum acceptable hold time. This would typically involve testing multiple samples at various time points within and beyond the proposed hold time.
- Data Provenance: Not specified, but likely laboratory-based controlled studies.
-
Functional Testing:
- Sample Size: Not explicitly stated. The study used "both contrived positive (MRSA added to negative matrix) and negative (negative matrix only) samples." It also notes "Each target of the Xpert SA Nasal Complete test was analyzed." This implies a sufficient number of samples to represent positive and negative outcomes for both SA and MRSA targets.
- Data Provenance: Not specified, but based on the description of "contrived positive" and "negative matrix," it is a retrospective laboratory-based study using controlled samples. The materials used (e.g., negative matrix) would be laboratory-sourced.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications
Not Applicable for this particular submission. The ground truth for the functional testing was established by the nature of the contrived samples:
- Contrived positive samples: MRSA added to negative matrix, meaning the positive status was known and intentionally created.
- Negative samples: Negative matrix only, meaning the negative status was known and intentionally created.
This type of study does not require human expert interpretation to establish the ground truth of the samples.
4. Adjudication Method for the Test Set
Not Applicable. As the ground truth was established by the deliberate creation of contrived positive and negative samples, no adjudication by human experts was required to determine the true status of the samples.
5. If a Multi Reader Multi Case (MRMC) Comparative Effectiveness Study Was Done
No, a MRMC comparative effectiveness study was not done. This submission (K243070) is for a device modification to expand compatible instruments rather than to assess human reader improvement with AI assistance. The device in question is an automated in vitro diagnostic test that provides a qualitative result (positive/negative) directly, without requiring human interpretation for its primary output.
6. If a Standalone (i.e. algorithm only without human-in-the-loop performance) Was Done
Yes, a standalone performance study was effectively done. The Xpert SA Nasal Complete test is an automated nucleic acid amplification test (NAAT). The "functional testing" described assesses the device's ability to correctly identify contrived positive and negative samples when run on the new GeneXpert Infinity Systems instruments, independently determining the presence or absence of the target DNA. This is a standalone performance evaluation of the device itself.
7. The Type of Ground Truth Used
The ground truth used for the functional testing was established by the deliberate creation of contrived samples. This includes:
- Contrived positive samples: MRSA added to a negative matrix, where the presence of the pathogen (MRSA) is known and controlled.
- Negative samples: Negative matrix only, where the absence of the pathogen is known and controlled.
This methods ensures a definitive and known ground truth.
8. The Sample Size for the Training Set
Not applicable/Not explicitly stated. The Xpert SA Nasal Complete test is a PCR-based diagnostic with specific primers and probes for target DNA. It is not typically a machine learning/AI model that undergoes "training" in the traditional sense with a distinct training set. The assay's design (primers, probes, thermocycling protocols) would have been developed and optimized during its initial development, but this isn't referred to as a "training set" in the context of this type of device. The current submission is a modification focusing on instrument compatibility.
9. How the Ground Truth for the Training Set Was Established
Not applicable. As noted above, the concept of a "training set" and its associated ground truth establishment is not directly relevant to this PCR-based diagnostic device in the context of this submission. The assay's analytical performance and target specificity are inherent to its biochemical design.
§ 866.1640 Antimicrobial susceptibility test powder.
(a)
Identification. An antimicrobial susceptibility test powder is a device that consists of an antimicrobial drug powder packaged in vials in specified amounts and intended for use in clinical laboratories for determining in vitro susceptibility of bacterial pathogens to these therapeutic agents. Test results are used to determine the antimicrobial agent of choice in the treatment of bacterial diseases.(b)
Classification. Class II (performance standards).