Predicate Devices

Reference Devices

Not Found

AI/ML (Artificial Intelligence / Machine Learning)

No
The description focuses on automated real-time PCR and standard laboratory controls, with no mention of AI or ML algorithms for data analysis or interpretation.

Therapeutic

No.

This device is a qualitative in vitro diagnostic test intended for the detection of methicillin-resistant Staphylococcus aureus (MRSA) DNA to aid in the prevention and control of MRSA infections. It is not intended to diagnose, guide, or monitor treatment, which would classify it as a therapeutic device.

Diagnostic

Yes

The "Intended Use / Indications for Use" section explicitly states that the Xpert® MRSA NxG Assay is "a qualitative in vitro diagnostic test intended for the detection of methicillin-resistant Staphylococcus aureus (MRSA) DNA."

SaMD (Software as a Medical Device)

No

The device is an in vitro diagnostic test that utilizes hardware components (GeneXpert Instrument Systems, single-use cartridges, collection devices) and reagents to perform real-time PCR. While software is involved in controlling the instrument and processing results, it is not a standalone software-only medical device.

IVD (In Vitro Diagnostic)

Yes, this device is an IVD (In Vitro Diagnostic).

Here's why:

Intended Use/Indications for Use: The very first sentence explicitly states it is a "qualitative in vitro diagnostic test". It is intended for the detection of MRSA DNA directly from nasal swabs, which are biological specimens taken from the human body. This aligns perfectly with the definition of an in vitro diagnostic device.
Device Description: The description further reinforces this by calling it an "automated real-time polymerase chain reaction (PCR) in vitro diagnostic test". It describes how it analyzes biological samples (nasal swabs) to detect specific markers (MRSA DNA) outside of the body.
Performance Studies: The document details clinical performance studies using human nasal specimens, comparing the device's results to a reference method (culture and susceptibility testing). This is standard practice for validating the performance of IVD devices.
Key Metrics: The document provides key metrics like Sensitivity, Specificity, PPV, and NPV, which are crucial for evaluating the diagnostic accuracy of an IVD.
Predicate Device(s): The mention of a predicate device (BD MAXTM MRSA XT, K133605) indicates that this device is being compared to another legally marketed IVD device, a common step in the regulatory process for IVDs.

All of these points strongly indicate that the Xpert® MRSA NxG Assay is an In Vitro Diagnostic device.

PCCP (Predetermined Change Control Plan) Authorized

N/A

Overview

Intended Use / Indications for Use

The Xpert® MRSA NxG Assay, performed on the GeneXpert® Instrument Systems, is a qualitative in vitro diagnostic test intended for the detection of methicillin-resistant Staphylococcus aureus (MRSA) DNA directly from nasal swabs in patients at risk for nasal colonization. The test utilizes automated real-time polymerase chain reaction (PCR) for the amplification of MRSA-specific DNA targets and fluorogenic target-specific hybridization probes for the real-time detection of the amplified DNA. The Xpert MRSA NxG Assay is intended to aid in the prevention and control of MRSA infections in healthcare settings. The Xpert MRSA NxG Assay is not intended to diagnose, guide, or monitor treatment for MRSA infections, or provide results of susceptibility to methicillin. A negative result does not preclude MRSA nasal colonization. Concomitant cultures are necessary to recover organisms for epidemiological typing or for further susceptibility testing.

Product codes (comma separated list FDA assigned to the subject device)

NQX, OOI

Device Description

The Xpert MRSA NxG Assay is an automated real-time polymerase chain reaction (PCR) in vitro diagnostic test for qualitative detection of methicillin-resistant Staphylococcus aureus (MRSA) directly from nasal swab specimens of patients at risk for colonization with MRSA in a healthcare setting.

The Xpert MRSA NxG Assay is performed on the Cepheid GeneXpert® Instrument Systems (GeneXpert Dx, GeneXpert Infinity-48, GeneXpert Infinity-48s, and GeneXpert Infinity-80 systems). The GeneXpert Instrument System platform automates sample preparation, amplification and real-time detection.

The GeneXpert Instrument Systems require the use of single-use, disposable cartridges (the Xpert MRSA NxG cartridges) that hold the PCR reagents and host the PCR process. Because the cartridges are self-contained and specimens never come into contact with working parts of the instrument modules, cross-contamination between samples is minimized.

The Xpert MRSA NxG Assay includes reagents for the detection of target MRSA DNA. The primers and probes in the Xpert MRSA NxG Assay detect proprietary sequences for the gene for methicillin/oxacillin resistance (mecA and mecC), and staphylococcal cassette chromosome mec (SCCmec), which is inserted into the SA chromosomal attB site. A Sample Processing Control (SPC) and a Probe Check Control (PCC) are internal controls utilized by the GeneXpert Instrument System platform. The SPC is present to control for adequate processing of the target bacteria and to monitor for the presence of inhibitor(s) in the PCR assay to avoid false-negative results. The Probe Check Control verifies reagent rehydration, real-time PCR tube filling in the cartridge, probe integrity, and dye stability.

The single-use, multi-chambered fluidic cartridges are designed to complete sample preparation and real-time PCR for the detection of genomic DNA from methicillinresistant Staphylococcus aureus (MRSA) in 70 minutes or less. The GeneXpert Instrument Systems, comprised of the GeneXpert Dx Systems and the GeneXpert Infinity Systems, have 1 to 80 randomly accessible modules, depending upon the instrument, that are each capable of performing separate sample preparation and real-time PCR and RT-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 RT-PCR and detection.

Nasal swab specimens are collected using the Cepheid Sample Collection Device and are transported to the laboratory or designated GeneXpert testing area. The nasal swab specimen is placed in a tube containing 2 mL of Elution Reagent. Following a brief vortexing of the sample, the entire contents of the Elution Reagent tube are transferred to the sample chamber of the Xpert MRSA NxG cartridge using a transfer pipette. For nasal swab specimens that are collected using Copan Liquid Amies Elution Swab (ESwab) collection and transport system, 300 uL of liquid sample is transferred to a tube containing 2 mL of Elution Reagent. Following a brief vortexing of the sample, the entire contents of the Elution Reagent tube are transferred to the sample chamber of the Xpert MRSA NxG cartridge using a transfer pipette. The user initiates a test from the system user interface and places the cartridge into the GeneXpert instrument platform, which performs hands-off real-time, multiplex PCR for detection of DNA. The results are automatically generated at the end of the process in a report that can be viewed and printed.

Mentions image processing

Not Found

Mentions AI, DNN, or ML

Not Found

Input Imaging Modality

Not Found

Anatomical Site

Nasal swabs

Indicated Patient Age Range

Not Found

Intended User / Care Setting

healthcare settings.
CLIA Moderate Complexity and High Complexity labs

Description of the training set, sample size, data source, and annotation protocol

Not Found

Description of the test set, sample size, data source, and annotation protocol

Clinical Performance Study 1 (Rayon Swab):

Sample Size: 1103 eligible Rayon swab specimens.
Data Source: Nasal specimens collected from individuals at risk for nasal colonization of methicillin-resistant S. aureus (MRSA) from eight investigational sites within the US and outside of the US.
Annotation Protocol: The device results were compared to a reference method consisting of both a direct culture on MRSA selective chromogenic medium and enriched culture. Enrichment involved Trypticase Soy Broth (TSB) with 6.5% Sodium Chloride followed by subculture on Blood Agar (BA) and MRSA selective chromogenic medium. Identification of presumptive S. aureus colonies was confirmed with Gram stain, and catalase and coagulase testing. MRSA was confirmed by susceptibility testing with a Cefoxitin disk (30µg). The reference method result was considered positive for MRSA if the presence of MRSA was confirmed in either direct culture or enriched culture.

Clinical Performance Study 2 (ESwab):

Sample Size: 846 eligible ESwab specimens.
Data Source: Nasal specimens collected from individuals at risk for nasal colonization of methicillin-resistant S. aureus (MRSA) from six investigational sites within the US.
Annotation Protocol: The device results were compared to a reference method consisting of both a direct culture on MRSA selective chromogenic medium and enriched culture. Enrichment involved Trypticase Soy Broth (TSB) with 6.5% Sodium Chloride followed by subculture on Blood Agar (BA) and MRSA selective chromogenic medium. Identification of presumptive S. aureus colonies was confirmed with Gram stain, and catalase and coagulase testing. MRSA was confirmed by susceptibility testing with a Cefoxitin disk (30µg). The reference method result was considered positive for MRSA if the presence of MRSA was confirmed in either direct culture or enriched culture.

Summary of Performance Studies (study type, sample size, AUC, MRMC, standalone performance, key results)

Study Type: Clinical Performance Studies (prospective, multi-site investigational studies) and Non-Clinical Analytical Studies (Analytical Sensitivity, Analytical Specificity, Microbial Interference, Analytical Reactivity, Interfering Substances Study, Carry-Over Contamination, Reproducibility Study).

Clinical Performance - Rayon Swab:

Sample Size: 1103 eligible Rayon swab specimens.
Standalone Performance: Sensitivity: 91.0%, Specificity: 96.9%, PPV: 78.7%, NPV: 98.9%.
Key Results: The Xpert MRSA NxG Assay demonstrated 91.0% sensitivity and 96.9% specificity relative to the reference culture method.

Clinical Performance - ESwab:

Sample Size: 846 eligible ESwab specimens.
Standalone Performance: Sensitivity: 92.9%, Specificity: 97.6%, PPV: 83.5%, NPV: 99.1%.
Key Results: The Xpert MRSA NxG Assay demonstrated 92.9% sensitivity and 97.6% specificity relative to the reference culture method.

Clinical Performance - Combined Rayon Swab and ESwab:

Sample Size: 1949 total specimens (1103 Rayon + 846 ESwab).
Standalone Performance: Sensitivity: 91.8%, Specificity: 97.2%, PPV: 80.8%, NPV: 98.9%.
Key Results: Data from both collection devices were poolable, showing overall 91.8% sensitivity and 97.2% specificity.

Analytical Sensitivity (Limit of Detection - LoD):

Study Type: Analytical study on 13 individual MRSA strains with two types of swabs.
Key Results:
- Rayon swab: LoD was 302 CFU (at 95% confidence).
- ESwab: LoD was 812 CFU (at 95% confidence).

Analytical Specificity (Cross-reactivity):

Study Type: Analytical study testing 152 potentially cross-reactive microorganisms and human cells.
Key Results: Analytical specificity was 100%, with all tested organisms and human cells reported as "MRSA NOT DETECTED".

Microbial Interference:

Study Type: Analytical study evaluating the inhibitory effects of 9 common commensal bacterial strains.
Key Results: None of the tested microorganisms were found to cross-react or interfere with MRSA detection.

Analytical Reactivity (Inclusivity):

Study Type: Analytical study testing 196 methicillin-resistant Staphylococcus aureus strains.
Key Results: All 196 MRSA strains were correctly reported as "MRSA DETECTED".

Interfering Substances Study:

Study Type: Analytical study evaluating 19 substances that may be present in nasal swab specimens.
Key Results: 16 substances were correctly identified without interference. Potential inhibitory effects (delay in Ct values) were observed with Nasonex 50% (v/v), Flonase 50% (v/v), and Beconase at 40% (v/v) and 50% (v/v), but no false negative results were reported.

Carry-Over Contamination:

Study Type: Analytical study testing negative samples after very high positive samples.
Sample Size: 40 positive and 42 negative samples.
Key Results: All 40 positive samples were correctly reported as "MRSA DETECTED", and all 42 negative samples were correctly reported as "MRSA NOT DETECTED", demonstrating no carry-over contamination.

Reproducibility Study:

Study Type: Multi-site study with 5 samples tested at varying concentrations across 3 sites by 2 operators on 6 days.
Key Results: High reproducibility, with total agreement by sample ranging from 98.6% to 100%. Coefficient of variation for fluorescence signal (Ct values) indicated good reproducibility across sites, days, lots, operators, and within-assay.

Key Metrics (Sensitivity, Specificity, PPV, NPV, etc.)

Rayon Swab:

Sensitivity: 91.0% (95% CI: 84.6-94.9)
Specificity: 96.9% (95% CI: 95.7-97.8)
PPV: 78.7% (95% CI: 71.3-84.7)
NPV: 98.9% (95% CI: 98.0-99.4)

ESwab:

Sensitivity: 92.9% (95% CI: 86.0-96.5)
Specificity: 97.6% (95% CI: 96.2-98.5)
PPV: 83.5% (95% CI: 75.4-89.3)
NPV: 99.1% (95% CI: 98.1-99.5)

Combined Rayon Swab and ESwab:

Sensitivity: 91.8% (95% CI: 87.4-94.8)
Specificity: 97.2% (95% CI: 96.3-97.9)
PPV: 80.8% (95% CI: 75.5-85.2)
NPV: 98.9% (95% CI: 98.3-99.3)

Predicate Device(s): If the device was cleared using the 510(k) pathway, identify the Predicate Device(s) K/DEN number used to claim substantial equivalence and list them here in a comma separated list exactly as they appear in the text. List the primary predicate first in the list.

BD MAXTM MRSA XT [510(k) # K133605]

Reference Device(s): Identify the Reference Device(s) K/DEN number and list them here in a comma separated list exactly as they appear in the text.

Not Found

Predetermined Change Control Plan (PCCP) - All Relevant Information for the subject device only (e.g. presence / absence, what scope was granted / cleared under the PCCP, any restrictions, etc).

Not Found

Regulation Number and Section

§ 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).

Summary

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Image /page/0/Picture/1 description: The image is a black and white logo for the Department of Health & Human Services - USA. The logo is circular in shape, with the text "DEPARTMENT OF HEALTH & HUMAN SERVICES - USA" arranged around the perimeter of the circle. In the center of the circle is an emblem that features a stylized representation of three human profiles facing to the right. The profiles are stacked on top of each other, creating a sense of depth and unity.

Public Health Service

Food and Drug Administration 10903 New Hampshire Avenue Document Control Center - WO66-G609 Silver Spring, MD 20993-0002

November 23, 2016

CEPHEID JIM KELLY, Ph.D. EXECUTIVE DIRECTOR, REGULATORY AFFAIRS 904 CARRIBEAN DRIVE SUNNYVALE CA 94089

Re: K162444 Trade/Device Name: Xpert MRSA NxG Regulation Number: 21 CFR 866.1640 Regulation Name: Antimicrobial test powder Regulatory Class: II Product Code: NQX, OOI Dated: August 30, 2016 Received: August 31, 2016

Dear Dr. Kelly:

We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration. Please note: CDRH does not evaluate information related to contract liability warranties. We remind you, however, that device labeling must be truthful and not misleading.

If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations, Title 21, Parts 800 to 898. In addition, FDA may publish further announcements concerning your device in the Federal Register.

Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Parts 801 and 809); medical device reporting (reporting of medical device-related adverse events) (21 CFR 803); good manufacturing practice requirements as set forth in the quality systems (OS) regulation (21 CFR Part 820); and if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.

1

If you desire specific advice for your device on our labeling regulations (21 CFR Parts 801 and 809), please contact the Division of Industry and Consumer Education at its toll-free number (800) 638 2041 or (301) 796-7100 or at its Internet address

http://www.fda.gov/MedicalDevices/Resourcesfor You/Industry/default.htm. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR Part 807.97). For questions regarding the reporting of adverse events under the MDR regulation (21 CFR Part 803), please go to

http://www.fda.gov/MedicalDevices/Safety/ReportaProblem/default.htm for the CDRH's Office of Surveillance and Biometrics/Division of Postmarket Surveillance.

You may obtain other general information on your responsibilities under the Act from the Division of Industry and Consumer Education at its toll-free number (800) 638-2041 or (301) 796-7100 or at its Internet address

http://www.fda.gov/MedicalDevices/ResourcesforYou/Industry/default.htm.

Sincerely yours,

Ribhi Shawar -S

For Uwe Scherf, M.Sc., Ph.D. Director Division of Microbiology Devices Office of In Vitro Diagnostics and Radiological Health Center for Devices and Radiological Health

Enclosure

2

Indications for Use

510(k) Number (if known) K162444

Device Name Xpert MRSA NxG

Indications for Use (Describe)

The Xpert® MRSA NxG Assay, performed on the GeneXpert® Instrument Systems, is a qualitative in vitro diagnostic test intended for the detection of methicillin-resistant Staphylococcus aureus (MRSA) DNA directly from nasal swabs in patients at risk for nasal colonization. The test utilizes automated real-time polymerase chain reaction (PCR) for the amplification of MRSA-specific DNA targets and fluorogenic target-specific hybridization probes for the real-time detection of the amplified DNA. The Xpert MRSA NxG Assay is intended to aid in the prevention and control of MRSA infections in healthcare settings. The Xpert MRSA NxG Assay is not intended to diagnose, guide, or monitor treatment for MRSA infections, or provide results of susceptibility to methicillin. A negative result does not preclude MRSA nasal colonization. Concomitant cultures are necessary to recover organisms for epidemiological typing or for further susceptibility testing.

Type of Use (Select one or both, as applicable)
-------------------------------------------------

X Prescription Use (Part 21 CFR 801 Subpart D)

Over-The-Counter Use (21 CFR 801 Subpart C)

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510(k) Summary

As required by 21 CFR Section 807.92(c).

| Submitted by: | Cepheid
904 Caribbean Drive
Sunnyvale, CA 90489
Phone number: (847) 228-3299
Fax number: (847) 890-6589 |
|-------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Contact: | Scott A. Campbell, PhD, MBA |
| Date of Preparation: | November 8, 2016 |
| Device: | |
| Trade name: | Xpert® MRSA NxG |
| Common name: | Xpert MRSA NxG Assay |
| Type of Test: | Qualitative real-time polymerase chain reaction (PCR) assay
for the amplification and detection of methicillin-resistant
Staphylococcus aureus (MRSA) DNA. |
| Regulation number/
Classification name/
Product code: | 866.1640 /System, Nucleic acid amplification test, DNA,
methicillin resistant Staphylococcus aureus , Direct
specimen/NQX
862.2570/Instrumentation for clinical multiplex test
systems/OOI |
| Classification
Advisory Panel | Microbiology (83) |
| Prescription Use | Yes |
| Predicate Device
Assay: | BD MAXTM MRSA XT
[510(k) # K133605] |

4

Device Description:

The Xpert MRSA NxG Assay is an automated real-time polymerase chain reaction (PCR) in vitro diagnostic test for qualitative detection of methicillin-resistant Staphylococcus aureus (MRSA) directly from nasal swab specimens of patients at risk for colonization with MRSA in a healthcare setting.

The Xpert MRSA NxG Assay is performed on the Cepheid GeneXpert® Instrument Systems (GeneXpert Dx, GeneXpert Infinity-48, GeneXpert Infinity-48s, and GeneXpert Infinity-80 systems). The GeneXpert Instrument System platform automates sample preparation, amplification and real-time detection.

The GeneXpert Instrument Systems require the use of single-use, disposable cartridges (the Xpert MRSA NxG cartridges) that hold the PCR reagents and host the PCR process. Because the cartridges are self-contained and specimens never come into contact with working parts of the instrument modules, cross-contamination between samples is minimized.

The Xpert MRSA NxG Assay includes reagents for the detection of target MRSA DNA. The primers and probes in the Xpert MRSA NxG Assay detect proprietary sequences for the gene for methicillin/oxacillin resistance (mecA and mecC), and staphylococcal cassette chromosome mec (SCCmec), which is inserted into the SA chromosomal attB site. A Sample Processing Control (SPC) and a Probe Check Control (PCC) are internal controls utilized by the GeneXpert Instrument System platform. The SPC is present to control for adequate processing of the target bacteria and to monitor for the presence of inhibitor(s) in the PCR assay to avoid false-negative results. The Probe Check Control verifies reagent rehydration, real-time PCR tube filling in the cartridge, probe integrity, and dye stability.

The single-use, multi-chambered fluidic cartridges are designed to complete sample preparation and real-time PCR for the detection of genomic DNA from methicillinresistant Staphylococcus aureus (MRSA) in 70 minutes or less. The GeneXpert Instrument Systems, comprised of the GeneXpert Dx Systems and the GeneXpert Infinity Systems, have 1 to 80 randomly accessible modules, depending upon the instrument, that are each capable of performing separate sample preparation and real-time PCR and RT-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 RT-PCR and detection.

Nasal swab specimens are collected using the Cepheid Sample Collection Device and are transported to the laboratory or designated GeneXpert testing area. The nasal swab specimen is placed in a tube containing 2 mL of Elution Reagent. Following a brief vortexing of the sample, the entire contents of the Elution Reagent tube are transferred to the sample chamber of the Xpert MRSA NxG cartridge using a transfer pipette. For nasal

5

swab specimens that are collected using Copan Liquid Amies Elution Swab (ESwab) collection and transport system, 300 uL of liquid sample is transferred to a tube containing 2 mL of Elution Reagent. Following a brief vortexing of the sample, the entire contents of the Elution Reagent tube are transferred to the sample chamber of the Xpert MRSA NxG cartridge using a transfer pipette. The user initiates a test from the system user interface and places the cartridge into the GeneXpert instrument platform, which performs hands-off real-time, multiplex PCR for detection of DNA. The results are automatically generated at the end of the process in a report that can be viewed and printed.

Device Intended Use:

The Xpert® MRSA NxG Assay, performed on the GeneXpert® Instrument Systems, is a qualitative in vitro diagnostic test intended for the detection of methicillin-resistant Staphylococcus aureus (MRSA) DNA directly from nasal swabs in patients at risk for nasal colonization. The test utilizes automated real-time polymerase chain reaction (PCR) for the amplification of MRSA-specific DNA targets and fluorogenic target-specific hybridization probes for the real-time detection of the amplified DNA. The Xpert MRSA NxG Assay is intended to aid in the prevention and control of MRSA infections in healthcare settings. The Xpert MRSA NxG Assay is not intended to diagnose, guide, or monitor treatment for MRSA infections, or provide results of susceptibility to methicillin. A negative result does not preclude MRSA nasal colonization. Concomitant cultures are necessary to recover organisms for epidemiological typing or for further susceptibility testing.

Substantial Equivalence:

The Xpert MRSA NxG Assay is substantially equivalent to the BD MAX™M MRSA XT assay [510(k) #K133605]. The performance of the Xpert MRSA NxG Assay was evaluated in two multi-site prospective clinical studies in which the performance of the Xpert MRSA NxG Assay was determined relative to culture and susceptibility testing. The results of the studies demonstrated that the performance of the Xpert MRSA NxG Assay is substantially equivalent to the predicate device.

Table 8-1 shows the similarities and differences between the Xpert MRSA NxG Assay and the predicate device.

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Similarities
Item	Device	Predicate Device
	Cepheid Xpert MRSA NxG
Assay	BD MAX™ MRSA XT Assay
510(k) Number	To be assigned	K133605
Regulation	Same	866.1640
Product Code	Same	NQX
Device Class	Same	II
Intended Use	The Xpert® MRSA NxG Assay,
performed on the GeneXpert®
Instrument Systems, is a
qualitative in vitro diagnostic test
intended for the detection of
methicillin-resistant
Staphylococcus aureus (MRSA)
DNA directly from nasal swabs
in patients at risk for nasal
colonization. The test utilizes
automated real-time polymerase
chain reaction (PCR) for the
amplification of MRSA-specific
DNA targets and fluorogenic
target-specific hybridization
probes for the real-time detection
of the amplified DNA. The Xpert
MRSA NxG Assay is intended to
aid in the prevention and control
of MRSA infections in
healthcare settings. The Xpert
MRSA NxG Assay is not
intended to diagnose, guide, or
monitor treatment for MRSA
infections, or provide results of
susceptibility to methicillin. A
negative result does not preclude
MRSA nasal colonization.
Concomitant cultures are
necessary to recover organisms
for epidemiological typing or for
further susceptibility testing.	The BD MAX™ MRSA XT assay
performed on the BD MAX™
System is an automated
qualitative in vitro diagnostic test
for the direct detection of
methicillin-resistant
Staphylococcus aureus (MRSA)
DNA from nasal swabs in
patients at risk for nasal
colonization. The test utilizes
real-time polymerase chain
reaction (PCR) for the
amplification of MRSA DNA and
fluorogenic target-specific
hybridization probes for the
detection of the amplified DNA.
The BD MAX™ MRSA XT assay
is intended to aid in the
prevention and control of MRSA
infections in healthcare settings.
It is not intended to
diagnose MRSA infections nor
guide or monitor treatment for
MRSA infections. A negative
result does not preclude nasal
colonization. Concomitant
cultures are necessary to recover
organisms for epidemiological
typing or for further susceptibility
testing.
Similarities
Item	Device	Predicate Device
	Cepheid Xpert MRSA NxG Assay	BD MAX™ MRSA XT Assay
Mode of Detection of Methicillin Resistance in S. aureus	Same	Presence of SCCmec cassette at orfX junction (specific to S. aureus) and mecA or mecC genes
Specimen Type	Same	Nasal swabs
Technological Principles	Same	Nucleic acid amplication (DNA); real-time PCR; fluorogenic target-specific hybridization probes
Assay Controls	Same	Specimen Processing Control (SPC)
Assay Results	Same	Qualitative
Laboratory Users	Same	CLIA Moderate Complexity and High Complexity labs

Table 8-1: Comparison of Similarities and Differences of the Xpert MRSA NxG Assay with the Predicate Device

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Primary Differences
Item	New Device	Predicate Device
	Cepheid Xpert MRSA NxG
Assay	BD MAX™ MRSA XT
Assay
Instrument System	Cepheid GeneXpert
Instrument System	BD MAX System
Early assay
termination function	Yes
(for positive samples)	No

The Xpert MRSA NxG Assay has the same general intended use as the predicate device and has the same technological characteristics as the predicate device. The differences between the Xpert MRSA NxG Assay and the predicate device do not raise different questions of safety and effectiveness. The clinical study demonstrates that the Xpert MRSA NxG Assay is acceptable for its intended use with inexperienced lab users and is substantially equivalent to the predicate device described above.

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Non-Clinical Studies:

Analytical Sensitivity (Limit of Detection)

Studies were performed to determine the analytical sensitivity or Limit of Detection (LoD) of the Xpert MRSA NxG Assay using two different collection kits (the Cepheid Sample Collection Device P/N 900-0370 or Copan P/N 139CFA, referred to as the "rayon swab" and the ESwab collection kit, Copan P/N 480C or Becton Dickinson P/N 220245 referred to as the "ESwab" refer to Section 6.3). The LoD is the lowest concentration of sample (reported as CFU/swab or CFU/mL in Elution Reagent) that can be reproducibly distinguished from negative samples 95% of the time with 95% confidence. This study determined the lowest concentration of methicillin-resistant Staphylococcus aureus (MRSA) cells diluted into simulated nasal matrix that can be detected using the Xpert MRSA NxG Assay The simulated nasal matrix consisted of 5% (w/v) porcine mucin and 1% (v/v) human whole blood in a 1X Phosphate Buffered Saline (PBS) solution with 15% (v/v) glycerol.

The analytical sensitivity of the Xpert MRSA NxG Assay was assessed following the guidance in Clinical and Laboratory Standards Institute (CLSI) document EP17-A2 using two lots of reagents tested across three testing days with thirteen (13) individual MRSA strains and the two types of swabs (rayon swab and ESwab). The 13 individual strains represent SCCmec types I, II, III, IV, IVa, V, VI, VIII, IX, X and XI. These strains in the LoD study represent the most common healthcare-acquired (USA100) and most common community-acquired (USA400) MRSA strains that are characterized by pulsedfield gel electrophoresis (PFGE). Strains that contained heterogeneous subpopulations with respect to their oxacillin resistance phenotype were also included in the study.

The LoD was established by testing five concentration levels with two reagent lots. The LoD and 95% confidence interval (CI) were then estimated for each lot using logistic regression analysis. The logistic regression analysis does not rely on a single concentration but utilizes the logit function to incorporate the information from all levels tested in the model. The point estimates were calculated using a method of maximum likelihood estimates (MLE) of the logistic regression model parameters. The maximum estimated LoD observed per strain from the logistic regression analysis was used to establish the LoD claim. The LoD point estimates and 95% upper and lower confidence intervals for each MRSA SCCmec type tested are summarized in Table 8-2 and Table 8-3.

The results of this study indicate that the Xpert MRSA NxG Assay will produce a positive MRSA result 95% of the time with 95% confidence for a nasal swab (Rayon) containing 302 CFU (Table 8-2).

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| MRSA Strain | PFGE IDª | LOD Estimate
(Logistic Regression) (CFU/Swab) | | | LoD Estimate
In Elution
Reagent
(CFU/mL) |
|-----------------|----------|--------------------------------------------------|-----------------------|-----------------|---------------------------------------------------|
| | | Lower 95%
CI | LoD Point
Estimate | Upper 95%
CI | |
| Type I | USA500 | 72 | 91 | 136 | 46 |
| Type II | USA100 | 127 | 161 | 236 | 81 |
| Type III | unknown | 50 | 64 | 96 | 32 |
| Type IVa | USA400 | 46 | 58 | 84 | 29 |
| Type IV (Fin 7) | unknown | 256 | 302 | 392 | 151 |
| Type IVa | USA300 | 143 | 182 | 282 | 91 |
| Type V | USA1000 | 85 | 102 | 138 | 51 |
| Type VI | USA800 | 32 | 42 | 64 | 21 |
| Type VII | unknown | 95 | 128 | 235 | 64 |
| Type VIII | unknown | 139 | 163 | 233 | 82 |
| Type IX | unknown | 142 | 169 | 227 | 85 |
| Type X | unknown | 86 | 97 | 119 | 49 |
| Type XI (mecC) | unknown | 219 | 266 | 358 | 133 |

Table 8-2: 95% Confidence Intervals for Analytical LoD - MRSA (Ravon swab)

a. PFGE = Pulsed-field gel electrophoresis

The results of this study indicate that the Xpert MRSA NxG Assay will produce a positive MRSA result 95% of the time with 95% confidence for a nasal swab (ESwab) containing 812 CFU (Table 8-3).

| | PFGE IDª | LoD Estimate
(Logistic Regression) (CFU/swab) | | | LoD Estimate
In Elution |
|-----------------|----------|--------------------------------------------------|-----------------------|-----------------|----------------------------|
| MRSA Strain | | Lower
95% CI | LoD Point
Estimate | Upper
95% CI | Reagent
(CFU/mL) |
| Type I | USA500 | 285 | 343 | 469 | 45 |
| Type II | USA100 | 184 | 218 | 293 | 28 |
| Type III | unknown | 215 | 254 | 338 | 33 |
| Type IVa | USA400 | 134 | 167 | 245 | 22 |
| Type IV (Fin 7) | unknown | 656 | 812 | 1145 | 106 |
| Type IVa | USA300 | 470 | 563 | 733 | 73 |
| Type V | USA1000 | 378 | 465 | 671 | 61 |
| Type VI | USA800 | 71 | 89 | 128 | 12 |
| Type VII | unknown | 201 | 245 | 338 | 32 |
| Type VIII | unknown | 520 | 631 | 851 | 82 |
| Type IX | unknown | 311 | 377 | 533 | 49 |
| Type X | unknown | 149 | 166 | 215 | 22 |
| Type XI (mecC) | unknown | 597 | 734 | 998 | 96 |

Table 8-3: 95% Confidence Intervals for Analytical LoD — MRSA (ESwab)

a. PFGE = Pulsed-field gel electrophoresis

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Analytical Specificity (Cross-reactivity)

The analytical specificity of the Xpert MRSA NxG Assay was evaluated by testing a panel of one hundred and fifty-two potentially cross-reactive microorganisms that are methicillin-susceptible Staphylococcus aureus (MSSA), organisms phylogenetically related to Staphylococcus aureus (SA), and members of the nasal commensal microflora (e.g., other bacteria, viruses, and yeast) with the potential to cross-react with the Xpert MRSA NxG Assay. The one hundred and fifty two organisms tested were identified as either gram-positive (104), gram-negative (25), yeast (3), viruses (17), or Gram reaction indeterminate (3). Of these organisms, eighty-four were characterized as follows: twenty-three (23) were methicillin-susceptible, coagulase-negative Staphylococcus (MSCoNS). five (5) were methicillin-resistant, coagulase-negative Staphylococcus (MRCoNS), forty-seven (47) were methicillin-susceptible Staphylococcus aureus (MSSA), including two (2) empty cassette MSSA, and seven (7) borderline oxacillinresistant Staphylococcus aureus (BORSA) strains. Human cells were also tested in the study.

Evaluation of BORSA Strains: The seven well-characterized borderline oxacillinresistant Staphylococcus aureus (BORSA) strains that were tested included one "empty cassette" MSSA strain. Methicillin-resistant Staphylococcus aureus is resistant to all ßlactam drugs (with the exception of ceftaroline) through the alternative penicillin-binding protein PBP2a encoded by mecA or mecC. BORSA strains do not carry mecA/mecC gene, but exhibit an oxacillin minimum inhibitory concentration (MIC) > 2 and 106 CFU/mL for bacteria and >105 TCIDe6/mL for viruses. Human cells were tested at 10° cells/mL.

All microorganisms and the human cells were reported as MRSA NOT DETECTED by the Xpert MRSA NxG Assay. For the panel of one hundred and fifty-two potentially cross-reactive microorganisms and human cells evaluated in the study, the analytical specificity of the Xpert MRSA NxG Assay was 100%.

In silico analysis indicates that the Xpert MRSA NxG Assay may produce positive results with strains of Staphylococcus argenteus, a recently described species of Staphylococcus that is closely related to S. aureus, that carry an SCCmec cassette and mecA or mecC.

Microbial Interference

A study was conducted to assess the inhibitory effects of commensal microorganisms in nasal swab specimens on the performance of the Xpert MRSA NxG Assay. A panel of nine (9) bacterial strains, reported to be present in 10% or more of nasal cavities of healthy subjects, were evaluated using the Xpert MRSA NxG Assay (Table 8-4).

The nine commensal bacteria were spiked into the simulated nasal matrix at

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approximately 1.0 x 10° CFU/ mL in Elution Reagent and tested in the presence of MRSA (cross-reactivity) or in the absence of MRSA (interference). Two MRSA strains (Table 8-5) were used in this study and these strains prepared at approximately 3X LoD and tested in replicates of four. None of the potentially interfering microorganisms evaluated in the study were found to cross-react or interfere with the detection of any of the MRSA strains using the Xpert MRSA NxG Assay.

Strain	Strain ID
Staphylococcus aureus (MSSA)	15280
Staphylococcus epidermidis (MSSE)	ATCC 35984
Corynebacterium bovis	ATCC 7715
Streptococcus mutans	ATCC 25175
Proteus vulgaris	ATCC 29905
Haemophilus influenzae	ATCC 9007
Neisseria meningitidis	ATCC 700111
Moraxella catarrhalis	ATCC 43628
Streptococcus pneumoniae	ATCC 6303

Table 8-4: Commensal Bacterial Strains Tested in Microbial Interference

Table 8-5: MRSA Strains

Target	Strain ID
MRSA ( mecA )	MRSA Type II (NRSA70,N315)
MRSA ( mecC )	MRSA Type XI LGA251

Analytical Reactivity (Inclusivity)

One hundred and ninety-six methicillin-resistant Staphylococcus aureus strains were tested in this study. The strains tested represented Cooper and Feil Groups 1A, 1B, and 2, SCCmec types and subtypes (I, IA, II, III, IIIA, III-Hg, IV, IVa, IVb, IVc, IVc, V, VI, VII, VIII, IX, X and XI), - sequence types (STs), spa-types, PFGE types, and clonal complexes (CC). Known USA100, USA200, USA300, USA400, USA500, USA600, USA700. USA800. USA1000. USA1100. IBERIAN strains, heteroresistant strains, and novel mecC strain MRSALGA251 were also included in this study. A "challenge panel" of 59 well characterized MRSA strains that have Minimum Inhibitory Concentrations (MIC) for cefoxitin/oxacillin that span the measurable dynamic range were also included in this study. Oxacillin MIC values for these 59 strains ranged from 0.5 to >32 µg/mL.

All 196 MRSA strains were correctly reported as MRSA DETECTED using the Xpert MRSA NxG Assay.

Interfering Substances Study

Nineteen substances that may be present in nasal swab specimens with the potential to interfere with the performance of the Xpert MRSA NxG Assay were evaluated. The

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potentially interfering substances included mucous, human blood, nasal sprays or drops, nasal gels, nasal corticosteroids, FluMist, oral nasal anesthetics or analgesics, nasal antibiotics, antibacterials and antivirals. The substances, active ingredients, and concentrations tested are listed in Table 8-6. All interfering substances, with the exception of mucin, were initially tested at 50% (v/v) in a simulated nasal matrix for Negative (simulated matrix only) and MRSA-positive samples. Mucin was tested at 7% (w/v) in simulated nasal matrix for Negative (simulated matrix only) and MRSA-positive samples.

Buffer Controls (negative and positive) without interfering substances were included.

Positive samples were tested per interfering substance with two clinical MRSA strains. SCCmec Type II (mecA) and SCCmec Type XI (mecC1GA251), spiked at approximately 3X analytical LoD in simulated nasal matrix.

Replicates of eight positive and negative samples with each interfering substance were evaluated in this study. Negative samples in the presence of potentially interfering substance were tested to determine the impact on the performance of the sample processing control (SPC).

The effect of each potentially interfering substance on positive and negative samples was assessed by comparing the target cycle threshold (Ct) values generated in the presence of the potentially interfering substance to the Ct values of the buffer controls in the absence of the potentially interfering substance.

The positive and negative samples for 16 potentially interfering substances were correctly identified. Potentially inhibitory effects were observed in positive samples tested with Nasonex 50% (v/v), Flonase 50% (v/v), and Beconase at 40% (v/v) and 50% (v/v) due to delay in Ct values; however, none of the substances reported false negative test results. No interference was observed in positive samples tested with Nasonex 40% (v/v), Flonase 40% (v/v), and Beconase at 30% (v/v). This is addressed in Section 16, Limitations, in the package insert.

| Substance | Active Ingredient | Concentration
Tested |
|-----------------------------------|----------------------------------------------------------------------|-------------------------|
| Mucous (Mucin) | Porcine mucin representing densely
glycosylated proteins (mucous) | 7% (w/v) |
| Blood | Blood (Human) | 50% (v/v) |
| Aneferin Decongestant Spray | 0.05% Oxymetazoline Hydrochloride | 50% (v/v) |
| Azelastin Antihistamine Spray | 0.1% Azelastine Hydrochloride | 50% (v/v) |
| NasalCrom Allergy Symptom | 5.2 mg Cromolyn Sodium | 50% (v/v) |
| Neo-Synephrine Decongestant Spray | 0.5% Phenylephrine Hydrochloride | 50% (v/v) |
| Saline Nasal Moisturizing Spray | 0.65% Sodium Chloride | 50% (v/v) |

Table 8-6. Potential Interfering Nasal Substances Tested

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| Substance | Active Ingredient | Concentration
Tested |
|------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------|
| Zicam Nasal Gel
(Upper Respiratory Allergy
Symptom Relief) | 4x, 12x, 30x Luffa
operculata 12x, 30x
Galphimia glauca
12x, 30x, 200x Histaminum
hydrochloricum 12x, 30x, 200x Sulphur | 50% (v/v) |
| Nasonex (Nasal Allergy
Symptom Medication, inhaled | 0.05% Mometasone Furoate Monohydrate | 40%(v/v),
50% (v/v)a |
| Flonase | 0.05% Fluticasone Propionate | 40% (v/v),
50% (v/v)a |
| FluMist | Live intranasal influenza virus vaccine | 50% (v/v) |
| Finafta Multioral | 7.5% Benzocaine | 50% (v/v) |
| TobraDex | 0.3% Tobramycin, 0.1% Dexamethasone | 50% (v/v) |
| Bactroban | 2% Mupirocin | 50% (v/v) |
| Relenza | 5 mg Zanamivir | 50% (v/v) |
| Beconase® AQ | 0.05% or 3.6x10-5 g Beclomethasone | 30% (v/v),
40% (v/v)a,
50% (v/v)a |
| Nasacort® AQ | 0.06% or 4.4x10-5 g Triamcinolone
acetonide | 50% (v/v) |
| Rhinocort aqua® | 0.06% or 4.4x10-5 g Budesonide | 50% (v/v) |
| Flunisolide Nasal Solution USP,
0.025% | 0.03% or 1.9x10-5 g Flunisolide | 50% (v/v) |

a. Potential inhibitory effect observed for the concentration tested due to delay in Ct values.

Carry-Over Contamination

A study was conducted to demonstrate that single-use, self-contained GeneXpert cartridges prevent carry-over contamination in negative samples tested following very high MRSA-positive samples in the same GeneXpert module. The study consisted of a negative sample processed in the same GeneXpert module immediately following a very high positive sample. The MRSA-negative samples were composed of MSSE prepared in a simulated nasal matrix at a concentration ≥1.0 x 10 CFU/mL in the Elution Reagent. The MRSA-positive samples were composed of MRSA in a simulated nasal matrix at a concentration ≥1 x 10' CFU/mL in the Elution Reagent. The testing scheme was repeated 40 times between 2 GeneXpert instruments (one module per instrument) for a total of 41 runs per instrument (20 high positive samples per instrument and 21 negative samples per instrument). All 40 positive samples were correctly reported as MRSA DETECTED. All 42 negative samples were correctly reported as MRSA NOT DETECTED.

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Linearity

Not applicable, the Xpert MRSA NxG Assay is a qualitative assay.

Clinical Studies

Clinical Performance

Performance characteristics of the Xpert MRSA NxG Assay were determined in two separate prospective, multi-site investigational studies using nasal specimens collected from individuals at risk for nasal colonization of methicillin-resistant S. aureus (MRSA). In the first study, eight investigational sites within the US and outside of the US tested the Xpert MRSA NxG Assay with nasal swabs collected using the Cepheid Sample Collection Device (Rayon Swab). In the second study, six investigational sites within the US tested the Xpert MRSA NxG Assay with nasal swabs collected using the Liquid Amies Elution Swab (ESwab) Collection and Transport System. Not more than one specimen per subject was included in the studies and analyses.

The Xpert MRSA NxG Assay results were compared to reference culture and susceptibility results.

The comparative reference method consisted of both a direct culture on MRSA selective chromogenic medium and enriched culture. Enrichment of the specimen was performed in Trypticase Soy Broth (TSB) with 6.5% Sodium Chloride followed by subculture of the TSB 6.5% NaCl on to Blood Agar (BA) and MRSA selective chromogenic medium. Identification of presumptive S. aureus colonies from BA and MRSA colonies from the selective chromogenic medium plates was confirmed with Gram stain, and catalase and coagulase testing. MRSA was confirmed by susceptibility testing with a Cefoxitin disk (30µg). The reference method result was considered positive for MRSA if the presence of MRSA was confirmed in either direct culture or enriched culture.

Results Obtained with the Xpert MRSA NxG Assay in Comparison to the Reference Method using the Rayon Swab

A total of 1103 eligible Rayon swab specimens were tested by the Xpert MRSA NxG Assay and by the reference method. Relative to the reference method, the Xpert MRSA NxG Assay demonstrated a sensitivity and specificity of 91.0% and 96.9%, respectively (Table 8-7). For the population tested, the MRSA positive predictive value (PPV) was 78.7% and the negative predictive value (NPV) was 98.9%.

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	Reference Method
	MRSA	Positive	Negative	Total
Xpert MRSA NxG	Positive	111	30a	141
	Negative	11b	951	962
	Total	122	981	1103
Sensitivity: 91.0% (95% CI: 84.6-94.9)
Specificity: 96.9% (95% CI: 95.7-97.8)
PPV: 78.7% (95% CI: 71.3-84.7)
NPV: 98.9% (95% CI: 98.0-99.4)

Table 8-7: Xpert MRSA NxG Assay with Rayon Swab vs. Reference Method

a. 30/30 specimens with Xpert MRSA NxG false positive results were also

MRSA culture negative upon repeat subculture of the enrichment broth. b. 11/11 specimens with Xpert MRSA NxG false positive results were MRSA culture positive upon repeat subculture of the enrichment broth.

Results Obtained with the Xpert MRSA NxG Assay in Comparison to the Reference Method using the ESwab

A total of 846 eligible ESwab specimens were tested by the Xpert MRSA NxG Assay and by the reference method. Relative to the reference method, the Xpert MRSA NxG Assay demonstrated a sensitivity and specificity of 92.9% and 97.6%, respectively (Table 8-8). For the population tested. the MRSA positive predictive value (PPV) was 83.5% and the negative predictive value (NPV) was 99.1%.

	Reference Method
	MRSA	Positive	Negative	Total
Xpert MRSA
NxG	Positive	91	18a	109
	Negative	7b	730	737
	Total	98	748	846
Sensitivity: 92.9% (95% CI: 86.0-96.5)
Specificity: 97.6% (95% CI: 96.2-98.5)
PPV: 83.5% (95% CI: 75.4-89.3)
NPV: 99.1% (95% CI: 98.1-99.5)

Table 8-8: Xpert MRSA NxG Assay with ESwab vs. Reference Method

a. 17/18 specimens with Xpert MRSA NxG false positive results were also MRSA culture negative after repeat of subculture of the enrichment broth.

b. 6/7 specimens with Xpert MRSA NxG false negative results were MRSA culture positive after repeat subculture of the enrichment broth.

Results Obtained with the Xpert MRSA NxG Assay in Comparison to the Reference Method for the Rayon Swab and ESwab Combined

Table 8-9 shows the sensitivity and specificity analyses of the combined Xpert MRSA NxG Assay results with Rayon Swab and ESwab relative to the reference method.

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Reference Method
	MRSA	Positive	Negative	Total
Xpert MRSA
NxG	Positive	202	48	250
	Negative	18	1681	1699
	Total	220	1729	1949
Sensitivity: 91.8% (95% CI: 87.4-94.8)
Specificity: 97.2% (95% CI: 96.3-97.9)
PPV: 80.8% (95% CI: 75.5-85.2)
NPV: 98.9% (95% CI: 98.3-99.3)

Table 8-9: Xpert MRSA NxG Assay with Rayon Swab and ESwab Combined vs. Reference Methodª

a. Using the data from Tables 8-7 and 8-8, the Fisher's Exact Test (p-value = 0.81 for sensitivity and p-value = 0.46 for specificity) demonstrated that the data are poolable across collection devices (Rayon Swab and ESwab).

Reproducibility Study

A panel of five samples with varying concentrations of MRSA was tested four times per day on six different days by two different operators, at three sites (5 samples x 4 times/day x 6 days x 2 operators x 3 sites). Three lots of Xpert MRSA NxG Assay cartridges were used, with each representing two days of testing. The Xpert MRSA NxG Assay was performed according to the Xpert MRSA NxG Assay procedure. Each of the 5 samples was prepared in simulated nasal matrix at the concentration levels in Table 8-10. Results are summarized in Table 8-11.

Table 8-10: Reproducibility Panel

Panel Sample	Concentration Level
Neg	True negative (no target)
ModPos1, MRSA Type XI (mecC)	Moderate positive (~2-3x LoD)
LowPos1, MRSA Type XI (mecC)	LOD (~1x LoD)
ModPos2, MRSA Type II (mecA)	Moderate positive (~2-3x LoD)
LowPos2, MRSA Type II (mecA)	LoD (~1x LoD)

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	Site Operator				Site Operator				Site Operator
Sample	Op 1	Op 2	Site	Op 1	Op 2	Site	Op 1	Op 2	Site	% Total
Agreement by
Sample
Neg	100%
(24/24)	100%
(24/24)	100%
(48/48)	100%
(24/24)	100%
(24/24)	100%
(48/48)	100%
(24/24)	100%
(24/24)	100%
(48/48)	100%
(144/144)
ModPos1	100%
(24/24)	100%
(24/24)	100%
(48/48)	100%
(24/24)	100%
(24/24)	100%
(48/48)	100%
(24/24)	100%
(24/24)	100%
(48/48)	100%
(144/144)
LowPos1	100%
(24/24)	100%
(24/24)	100%
(48/48)	100%
(24/24)	100%
(24/24)	100%
(48/48)	100%
(24/24)	100%
(24/24)	100%
(48/48)	100%
(144/144)
ModPos2	100%
(24/24)	100%
(24/24)	100%
(48/48)	100%
(24/24)	100%
(24/24)	100%
(48/48)	100%
(24/24)	100%
(24/24)	100%
(48/48)	100%
(144/144)
LowPos2	95.8%
(23/24)	100%
(24/24)	97.9%
(47/48)	100%
(24/24)	100%
(24/24)	100%
(48/48)	100%
(24/24)	95.8%
(23/24)	97.9
(47/48)	98.6%
(142/144)

Table 8-11: Summary of Reproducibility Results: % Agreement by Study Site/Operator

The reproducibility of the Xpert MRSA NxG Assay was also evaluated in terms of the fluorescence signal expressed in Ct values for each target detected. The mean, standard deviation (SD), and coefficient of variation (CV) between-sites, between-days, betweenlots, between-operators and within-assay for each panel member are presented in Table 8-12.

| Sample | Assay
Channel
(Analyte) | Nb | Mean
Ct | Between-
Site | | Between-
Day | | Between-
Lot | | Between-
Operator | | Within-
Assay | | Total | |
|---------|-------------------------------|-----|------------|------------------|------------|-----------------|------------|-----------------|------------|----------------------|------------|------------------|------------|-------|------------|
| | | | | SD | CV
(%)c | SD | CV
(%)c | SD | CV
(%)c | SD | CV
(%)c | SD | CV
(%)c | SD | CV
(%)c |
| Neg | SPC | 144 | 32.3 | 0.0 | 0.0 | 0.0 | 0.0 | 0.3 | 0.9 | 0.3 | 0.8 | 0.8 | 2.3 | 0.8 | 2.6 |
| | mec | 144 | 29.9 | 0.0 | 0.0 | 0.0 | 0.0 | 0.4 | 1.4 | 0.0 | 0.0 | 1.1 | 3.5 | 1.1 | 3.8 |
| ModPos1 | SCC | 144 | 32.6 | 0.0 | 0.0 | 0.0 | 0.0 | 0.5 | 1.5 | 0.0 | 0.0 | 1.0 | 3.0 | 1.1 | 3.3 |
| | mec | 144 | 31.7 | 0.0 | 0.0 | 0.0 | 0.0 | 0.4 | 1.4 | 0.0 | 0.0 | 1.0 | 3.2 | 1.1 | 3.5 |
| LowPos1 | SCC | 144 | 34.3 | 0.0 | 0.0 | 0.0 | 0.0 | 0.5 | 1.5 | 0.0 | 0.0 | 0.9 | 2.7 | 1.1 | 3.1 |
| | mec | 144 | 31.2 | 0.0 | 0.0 | 0.3 | 0.9 | 0.2 | 0.5 | 0.0 | 0.0 | 0.9 | 3.0 | 1.0 | 3.1 |
| ModPos2 | SCC | 144 | 32.8 | 0.0 | 0.0 | 0.3 | 0.8 | 0.3 | 1.0 | 0.0 | 0.0 | 0.9 | 2.7 | 1.0 | 3.0 |
| | mec | 144 | 32.7 | 0.0 | 0.0 | 0.4 | 1.1 | 0.0 | 0.0 | 0.2 | 0.6 | 1.0 | 3.0 | 1.1 | 3.2 |
| LowPos2 | SCC | 144 | 34.4 | 0.0 | 0.0 | 0.4 | 1.1 | 0.0 | 0.0 | 0.1 | 0.3 | 1.0 | 3.0 | 1.1 | 3.3 |

Table 8-12: Summary of Reproducibility Data4

a. There were a total of 12 indeterminate results over the study (11 reported as "Error" and 1 as "Invalid"). All 12 produced valid test results upon repeat.

b. Results with non-zero Ct values out of 144.

c. (%) is contribution of variance of component to overall CV.

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Conclusions

The results of the nonclinical analytical and clinical performance studies summarized above demonstrate that the Xpert MRSA NxG Assay is substantially equivalent to the predicate device.