XPERT MRSA/SA BLOOD CULTURE ASSAY; GENEXPERT DX SYSTEMS (GX-I, GX-II, GX-IV, GX-XVI); GENEXPERT INFINITY-48 SYSTEM; GENE
Device Facts
| Record ID | K130894 |
|---|---|
| Device Name | XPERT MRSA/SA BLOOD CULTURE ASSAY; GENEXPERT DX SYSTEMS (GX-I, GX-II, GX-IV, GX-XVI); GENEXPERT INFINITY-48 SYSTEM; GENE |
| Applicant | Cepheid |
| Product Code | NQX · Microbiology |
| Decision Date | Jun 20, 2013 |
| Decision | SESE |
| Submission Type | Traditional |
| Regulation | 21 CFR 866.1640 |
| Device Class | Class 2 |
Intended Use
The Cepheid® Xpert® MRSA/SA Blood Culture Assay, performed on the GeneXpert® Instrument Systems, is a qualitative in vitro diagnostic test intended for the detection of Staphylococcus aureus (SA) and methicillin-resistant Staphylococcus aureus (MRSA) DNA directly from positive blood cultures. The assay utilizes automated real-time polymerase chain reaction (PCR) for the amplification of MRSA/SA specific DNA targets and fluorogenic target-specific hybridization probes for the real-time detection of the amplified DNA. The assay is performed directly on positive blood culture samples from BD BACTEC™ Plus Aerobic/F, BacT/ALERT® SA (Standard Aerobic) or VersaTREK REDOX 1® (aerobic) blood culture bottles that are determined by Gram Stain as Gram Positive Cocci in Clusters (GPCC) or as Gram Positive Cocci in singles (GPC). The Xpert MRSA/SA Blood Culture Assay is indicated for use in conjunction with other laboratory tests, such as culture, and clinical data available to the clinician as an aid in the detection of MRSA/SA from positive blood cultures. Subculturing of positive blood cultures is necessary to recover organisms for susceptibility testing or for epidemiological typing. The Cepheid Xpert MRSA/SA Blood Culture Assay is not intended to monitor treatment for MRSA/SA infections.
Device Story
The Xpert MRSA/SA Blood Culture Assay is a rapid, automated molecular diagnostic test for identifying MRSA and SA in positive blood culture bottles. Input consists of a 50 µL aliquot from a positive blood culture bottle showing Gram-positive cocci. The sample is transferred to a single-use, multi-chambered fluidic cartridge containing all necessary reagents. The cartridge is processed on the Cepheid GeneXpert Instrument System, which integrates sample purification, cell lysis via ultrasonic horn, and real-time PCR amplification. The system uses fluorogenic target-specific hybridization probes to detect spa, mecA, and SCCmec sequences. Results are provided in approximately 60 minutes. The device is used in clinical laboratory settings by laboratory personnel. The output is a qualitative result (MRSA/SA detected or not detected) displayed on a connected PC. This information aids clinicians in the rapid identification of MRSA/SA, facilitating timely clinical decision-making and appropriate patient management, though it does not replace standard culture-based susceptibility testing.
Clinical Evidence
Prospective multi-site clinical study (n=792 eligible specimens). Compared to reference culture/susceptibility testing. MRSA: PPA 98.1% (95% CI: 93.3-99.8%), NPA 99.6% (95% CI: 98.7-99.9%). SA: PPA 99.6% (95% CI: 97.7-100%), NPA 99.5% (95% CI: 98.4-99.9%). First-run success rate 96.1%.
Technological Characteristics
Fully-automated real-time PCR; multiplex detection of spa, mecA, and SCCmec targets. Disposable cartridge contains all reagents, ultrasonic lysis, and I-CORE thermocycler. Connectivity: Standalone system with PC interface. Calibration: NIST-traceable thermal/optical calibration. Software: GeneXpert/Xpertise.
Indications for Use
Indicated for qualitative detection of SA and MRSA DNA in positive blood culture bottles (BD BACTEC, BacT/ALERT, VersaTREK) containing Gram-positive cocci (clusters or singles). Intended as an aid in detection; not for monitoring treatment. Requires subculturing for susceptibility testing.
Regulatory Classification
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.
Predicate Devices
Related Devices
- K082140 — XPERT MRSA/SA BLOOD CULTURE ASSAY · Cepheid · Sep 29, 2008
- K190771 — Xpert MRSA/SA Blood Culture, GeneXpert Dx System, GeneXpert Infinity-48s System, GeneXpert Infinity-80 System · Cepheid · Apr 25, 2019
Submission Summary (Full Text)
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130894
#### 510(k) Summary 5.0
# JUN 2 0 2013
As required by 21 CFR Section 807.92(c).
| Submitted by: | Cepheid<br>904 Caribbean Drive<br>Sunnyvale, CA 90489<br>Phone number: (408) 400-8460<br>Fax number: (847) 510-0539 |
|---------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|
| Contact: | Kerry J. Flom, Ph.D. |
| Date of Preparation: | March 29, 2013 |
| Device: | |
| Trade name: | Xpert® MRSA/SA Blood Culture Assay |
| Common name: | Methicillin-resistant Staphylococcus aureus (MRSA) and<br>Staphylococcus aureus (SA) from positive blood culture<br>bottles assay. |
| Type of Test: | Nucleic Acid Amplification Test, DNA, Methicillin-resistant<br>Staphylococcus aureus (MRSA) and Staphylococcus aureus<br>(SA), qualitative |
| Regulation number/ | 866.1640 |
| Classification name/<br>Product code: | Antimicrobial susceptibility test powder<br>NQX |
| Classification<br>Advisory Panel | Microbiology (83) |
| Predicate Devices<br>Name(s): | Xpert MRSA/SA Blood Culture Assay (510(k) #K101879)<br>BD GeneOhm™ StaphSR Assay (510(k) #K071026) |
## Device Description:
The Cepheid Xpert® MRSA/SA Blood Culture Assay (Xpert MRSA/SA Blood Culture Assay) is a rapid, automated DNA test for the simultaneous qualitative detection of MRSA and SA DNA directly from blood culture bottle specimens that are detected as positive for microbial growth and shown to contain Gram Positive Cocci by Gram stain. The primers and probes in the Xpert MRSA/SA Assay detect 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 test 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 dye stability.
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The specimen for testing with the Xpert MRSA/SA Blood Culture Assay consists of an aliquot taken from a positive blood culture bottle. Using one of the disposable fixed 50 µL volume transfer pipettes provided with the test kit, an aliquot of the positive blood culture is transferred into a single-use tube of Elution Reagent, also provided with the kit. The Elution Reagent is briefly vortexed and the entire content is transferred to the "S" chamber of the disposable fluidic cartridge (the Xpert MRSA/SA Blood Culture Assay cartridge), after which the cartridge is ready to place on the instrument.
The assay is performed on the Cepheid GeneXpert Instrument Systems, which automate and integrate sample purification, nucleic acid amplification of the target sequences in simple or complex samples using real-time PCR. The systems consist of an instrument, personal computer, and preloaded software for running the tests and viewing the results. The GeneXpert Instrument Systems require the use of single-use disposable cartridges that hold the PCR reagents and host the PCR process. Because the cartridges are self-contained, crosscontamination between samples is minimized. In this platform, additional sample preparation, amplification, and real-time detection are all fully-automated and completely integrated. The Xpert MRSA/SA Blood Culture Assay performed on the GeneXpert Instrument Systems provides results in approximately 60 minutes.
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 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 purpose of this submission is to submit documentation to support proposed improvements to the current assay and changes to the Intended Use.
## Device Intended Use:
The Cepheid® Xpert® MRSA/SA Blood Culture Assay, performed on the GeneXpert® Instrument Systems, is a qualitative in vitro diagnostic test intended for the detection of Staphylococcus aureus (SA) and methicillin-resistant Staphylococcus aureus (MRSA) DNA directly from positive blood cultures. The assay utilizes automated real-time polymerase chain reaction (PCR) for the amplification of MRSA/SA specific DNA targets and fluorogenic targetspecific hybridization probes for the real-time detection of the amplified DNA. The assay is performed directly on positive blood culture samples from BD BACTEC™ Plus Aerobic/F, BacT/ALERT® SA (Standard Aerobic) or VersaTREK REDOX 1® (aerobic) blood culture bottles that are determined by Gram Stain as Gram Positive Cocci in Clusters (GPCC) or as Gram Positive Cocci in singles (GPC). The Xpert MRSA/SA Blood Culture Assay is indicated for use in conjunction with other laboratory tests, such as culture, and clinical data available to the clinician as an aid in the detection of MRSA/SA from positive blood cultures. Subculturing of positive blood cultures is necessary to recover organisms for susceptibility testing or for epidemiological typing. The Cepheid Xpert MRSA/SA Blood Culture Assay is not intended to monitor treatment for MRSA/SA infections.
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## Substantial Equivalence:
The Xpert MRSA/SA Blood Culture Assay is substantially equivalent to the BD GeneOhm™ StaphSR Assay (510(k) #K071026) and to the current Xpert MRSA/SA Blood Culture Assay (510(k) #K101879). All assays detect SA and MRSA from positive blood cultures and determine the presence of the target organisms through real-time PCR amplification and fluorogenic target-specific hybridization detection. A multi-center study was conducted to determine the performance characteristics of the device relative to the reference culture results and susceptibility testing (the current standard of care), and relative to the predicate devices. The test results showed the Xpert MRSA/SA Blood Culture Assay to be substantially equivalent to the current standard of care and the predicate devices.
Table 5.1 shows the similarities and differences between the Xpert MRSA/SA Blood Culture Assay and predicate assays.
| Table 5.1 |
|----------------------------------------------------------------------------|
| Similarities and Differences Between the Xpert MRSA/SA Blood Culture Assay |
| and the Predicate Devices |
| Similarities | | | |
|--------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------|---------------------------------------------------|
| Item | New Device<br>Xpert MRSA/SA Blood Culture Assay | Predicate Devices | |
| | | Current Xpert MRSA/SA Blood Culture Assay<br>(510(k) #K101879) | BD GeneOhm™<br>StaphSR Assay<br>(510(k) #K071026) |
| Intended Use | Rapid detection of MRSA and SA | Same | Same |
| Indication for Use | Identification of MRSA and SA colonization | Same | Same |
| Specimen Type | Positive Blood Culture | Same | Same |
| Technological Principles | Fully-automated nucleic acid amplification (DNA); real-time PCR | Same | Same |
| DNA Target Sequence | Sequence incorporating the insertion site ( <i>attB</i> ) of Staphylococcal Cassette Chromosome <i>mec</i> (SCC <i>mec</i> ) for detection of MRSA. | Same | Same |
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| | | Similarities | | |
|------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--|
| | New Device | Predicate Devices | | |
| Item | Xpert MRSA/SA<br>Blood Culture Assay | Current Xpert<br>MRSA/SA Blood<br>Culture Assay<br>(510(k) #K101879) | BD GeneOhm™<br>StaphSR Assay<br>(510(k) #K071026) | |
| Clinical<br>Comparison<br>Results: | Xpert MRSA/SA Blood<br>Culture Assay<br>Performance vs.<br>Reference Culture :<br>MRSA:<br>Positive % Agreement:<br>98.1%<br>Negative % Agreement:<br>99.6%<br>SA:<br>Positive % Agreement:<br>99.6%<br>Negative % Agreement:<br>99.5% | Xpert MRSA/SA Blood<br>Culture Assay<br>Performance vs.<br>Reference Culture :<br>MRSA:<br>Positive % Agreement:<br>100.0<br>Negative % Agreement:<br>100.0<br>SA:<br>Positive % Agreement:<br>100.0<br>Negative % Agreement:<br>99.4 | BD GeneOhm™<br>StaphSR Assay<br>Performance vs.<br>Reference Culture<br>methods :<br>MRSA:<br>Positive %<br>Agreement: 100.0<br>Negative %<br>Agreement: 98.2 -<br>100.0<br>SA:<br>Positive %<br>Agreement: 98.8 -<br>100.0<br>Negative %<br>Agreement: 96.5 -<br>100.0<br>[Data obtained from<br>the BD GeneOhm<br>StaphSR Assay<br>510(k) Summary] | |
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| | | Differences | | |
|------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------|--|
| Item | New Device<br>Xpert MRSA/SA Blood Culture Assay | Predicate Devices<br>Current Xpert MRSA/SA Blood Culture Assay<br>(510(k) #K101879) | BD GeneOhm™<br>StaphSR Assay<br>(510(k) #K071026) | |
| Test Cartridge | Same as current Xpert assay. | Disposable single-use, multi-chambered fluidic cartridge. | Disposable single-use PCR tube | |
| Instrument<br>System | Cepheid GeneXpert Dx Systems and GeneXpert Infinity Systems | Cepheid GeneXpert Dx System | Cepheid SmartCycler | |
| | | Differences | | |
| | New Device | Predicate Devices | | |
| Item | Xpert MRSA/SA<br>Blood Culture Assay | Current Xpert<br>MRSA/SA Blood<br>Culture Assay<br>(510(k) #K101879) | BD GeneOhm™<br>StaphSR Assay<br>(510(k) #K071026) | |
| Sample<br>Preparation | Self-contained and<br>automated after mixed<br>specimen is added to<br>cartridge. All other<br>reagents are contained<br>in the cartridge. | Self-contained and<br>automated after mixed<br>specimen and two<br>single-dose reagents are<br>added to cartridge. | Manual | |
| Probes | Same as current Xpert<br>assay. | TaqMan® Probes | Molecular Beacons | |
| Internal<br>Controls | Same as current Xpert<br>assay. | Sample processing<br>control (SPC) and probe<br>check control (PCC). | One internal reagent<br>control and external<br>positive and negative<br>controls required per run | |
| DNA Target<br>Sequence | Same as current Xpert<br>assay. | Sequence specific to<br>methicillin/oxacillin<br>resistance (mecA gene) | N/A | |
| Users | Same as current Xpert<br>assay. | Operators with no<br>clinical lab experience<br>to experienced clinical<br>laboratory<br>technologists. | CLIA High Complexity<br>Laboratory Users | |
| DNA Target<br>Sequence | Same as current Xpert<br>assay. | Sequence specific to<br>Staphylococcus aureus<br>species (spa gene) | Sequence specific to<br>Staphylococcus aureus<br>species (nuc gene) | |
| Ability to<br>identify<br>correctly<br>"Empty<br>Cassette<br>Variants" | Same as current Xpert<br>assay. | Yes, sequence specific<br>to Staphylococcus<br>aureus species (mecA<br>gene) | No | |
| Rapid test<br>results | Approximately 60<br>minutes to result. | Approximately 50<br>minutes to result. | Approximately 60-75<br>minutes to result. | |
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## Non-Clinical Studies:
## Analytical Inclusivity (Reactivity)
Two hundred fifty (250) SA strains (47 MSSA and 203 MRSA) from multiple sources were tested using the Xpert MRSA/SA Blood Culture Assay. Selections were made to represent the primary lineages with emphasis placed on the specific clonal complexes within which MRSA is predominantly observed. Lineages that contain MRSA and MSSA, as well as those that contain MSSA exclusively were included. When characterized by pulsed-field gel electrophoresis (PFGE), numerous USA types including USA100, the most common healthcare-acquired strain and USA300 and USA400, the most common communityacquired strains were also included.1 Strains representing "Empty Cassette" variants and heterogeneous strains identified as borderline oxacillin-resistant Staphylococcus aureus or BORSA were also tested.
All strains were tested in triplicate using 10 ul of stationary phase cell suspension diluted 1 million-fold. Colony forming units per assay (CFU/test) were determined by plate counts in triplicate. All results were reported correctly by the Xpert MRSA/SA Blood Culture Assay, except one specimen. The Xpert MRSA/SA Blood Culture Assay incorrectly identified one (1) SA strain (LGA251) as MSSA instead of MRSA. LGA251 contains a novel mecA gene representing a divergent mecA homologue (mecALGA25)) located in a novel staphylococcal chromosome mec element, designated SCCmec type XI. The mecA primers and probes in the MRSA/SA Blood Culture Assay will not detect the novel mecA gene in this strain due to mutations in the primer/probe binding regions. The mecA gene in this strain is only 70% homologous to the mecA gene in other known MRSA strains.
#### Limit of Detection
Studies were performed to determine the two-sided 95% confidence intervals for the analytical limit of detection (LoD) of SA cells and methicillin-resistant SA (MRSA) cells diluted into a blood culture matrix that can be detected by the Xpert MRSA/SA Blood Culture Assay. The matrix consisted of SA-free whole blood and MSSE (methicillinsusceptible Staphylococcus epidermidis) cells at 10° CFU/mL added to blood culture medium. The limit of detection is defined as the lowest number of colony forming units (CFU) per sample that can be reproducibly distinguished from negative samples with 95% confidence or the lowest concentration at which 19 of 20 replicates were positive.
For MRSA. 20 replicates were evaluated at each MRSA concentration tested (CFU/test) for 10 individual isolates representing SCCmec types I, II, III, IVa, IVd, V, VI, VII, and VIII. When characterized by pulsed-field gel electrophoresis (PFGE), USA100, the most common healthcare-acquired strain and USA400, one of the most common communityacquired strains were represented.
Cooper, J E and Feil, E J. 2006. The phylogeny of Staphylococcus aureus - which genes make the best intra-species markers? Microbiology 152:1297 - 1305.
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For SA, 20 replicates were evaluated at each SA concentration (CFU/test) for 3 individual SA isolates. USA types USA900 and USA1200 were represented.
Point estimates and confidence intervals were determined by probit regression using data (i.e., the number of positive results per number of replicates at each level) spanning a range of CFU/test loadings. The confidence intervals were determined using maximum likelihood estimates on the probit model parameters using the large sample variancecovariance matrix. The LoD point estimates and 95% upper and lower confidence intervals for each SA and each MRSA SCCmec type tested are summarized in Tables 5.2 and 5.3.
| SA Strain<br>ID | PFGE ID | Confirmed<br>LoD<br>(CFU/test)<br>[at least 19/20<br>positive] | LoD Estimate (Probit Regression<br>Analysis) (CFU/test) | | |
|-----------------|----------|----------------------------------------------------------------|---------------------------------------------------------|--------------|-----------------|
| | | | Lower<br>95% CI | LoD Estimate | Upper<br>95% CI |
| 102-04a | USA 1200 | 100 (19/20) | 60.4 | 74.5 | 101.6 |
| 29213b | unknown | 150 (19/20) | 120.1 | 138.2 | 172.7 |
| N7129a | USA900 | 300 (19/20) | 224.2 | 255.2 | 314.8 |
## Table 5.2: LoD and 95% Confidence Intervals - SA
Strain Source:
· American Type Culture Collection (ATCC), Manassas, VA., USA
Centers for Disease Control and Prevention (CDC), Atlanta, GA., USA
| MRSA Strain ID | PFGE ID | Confirmed LoD<br>(CFU/test)<br>[at least 19/20<br>positive] | LoD Estimate (Probit Regression Analysis)<br>(CFU/test) | Lower 95%<br>CI | LoD Estimate | Upper<br>95% CI |
|-------------------------|----------|-------------------------------------------------------------|---------------------------------------------------------|-----------------|--------------|-----------------|
| Type I (64/4176)a | USA500 | 350 (19/20) | | 332.3 | 366.8 | 433.5 |
| Type II (N315)b | USA100e | 175 (19/20) | | 113.7 | 137.0 | 178.1 |
| Type III (11373)b | unknown | 225 (19/20) | | 191.9 | 222.6 | 273.9 |
| Type IVa (MW2)b | USA400e | 350 (19/20) | | 313.1 | 356.1 | 427.0 |
| Type V (ST59)c | USA1000e | 250 (19/20) | | 218.2 | 243.1 | 282.3 |
| Type VI (HDE288)d,f | USA800e | 250 (19/20) | | 222.2 | 246.0 | 385.0 |
| Type VII (JCSC6082)a | unknown | 300 (19/20) | | 264.1 | 288.0 | 347.1 |
| Type VIII (WA MRSA-16)c | unknown | 400 (19/20) | | 348.7 | 386.7 | 499.1 |
| Type II (BK2464)b | USA100g | 125 (19/20) | | 94.3 | 116.1 | 162.0 |
| Type IVd (BK2529)b,f | USA500g | 200 (19/20) | | 120.8 | 148.8 | 202.5 |
## Table 5.3. LoD and 95% Confidence Intervals - MRSA
Strain Source:
"Teruyo Ito, Department of Bacteriology, School of Medicine Juntendo University, Tokyo, Japan
Barry Kreiswirth, Director Public Health Research Institute (PHRI), Newark, NJ., USA
"Geoffrey Coombs, Department of Microbiology and Infectious Diseases, Royal Perth Hospital, Perth WA
1 Herminia de Lancaste, Laboratory of Molecular Genetics, Instituto de Tecnologia (ITQB), Universidade Nova de Lisboa, Oeiras, Portugal
6K, Bonnstetter, et al., J Clin Micro 2007, p. 141-146; L. McDougal, et al., J Clin Micro 2003, p. 51 13-5120
THeterogeneous oxacillin-resistant isolates
8Barry Kreiswirth, personal communication
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The results of this study indicate that the Xpert MRSA/SA Blood Culture Assay will produce a positive SA result 95% of the time in a positive blood culture aliquot (50 µL) containing 300 CFU and a positive MRSA result 95% of the time for a positive blood culture aliquot (50 µL) containing 400 CFU.
## Linearity
Not applicable, the Xpert MRSA/SA Blood Culture Assay is a qualitative assay.
## Analytical Specificity (Exclusivity)
One hundred and one (101) strains were collected, quantitated, and tested using the Xpert MRSA/SA Blood Culture Assay. Of the 101 strains tested, 91 cultures were obtained from the American Type Culture Collection (ATCC), 1 was obtained from Culture Collection, University of Göteborg, Sweden (CCUG), 1 was obtained from Teruyo Ito. Juntendo University, Tokyo, Japan, 1 carbapenemase (KPC) producing Klebsiella pneumoniae strain was obtained from National Collection of Type Cultures (NCTC), UK and 7 strains were obtained from the Network on Antimicrobial Resistance in SA (NARSA). These strains represent species phylogenetically related to SA or those potentially encountered in the hospital environment.
The organisms tested were identified as either Gram positive (74), Gram negative (24), or yeast (3). Methicillin-sensitive, coagulase negative Staphylococcus, MSCoNS (27) and methicillin- resistant, coagulase negative Staphylococcus, MRCoNS (12) were included. The organisms were further classified as either aerobic (94) or anaerobic (7).
Three replicates of each isolate were tested at 1.7 - 3.2 McFarland units. Under the conditions of the study, all isolates were reported MRSA NEGATIVE; SA NEGATIVE; none of the isolates were detected by the Xpert MRSA/SA Blood Culture Assay. The analytical specificity was 100%.
### Potentially Interfering Substances
Substances that may be present in blood cultures with potential to interfere with the Xpert MRSA/SA Blood Culture Assay were tested in the interfering substance study. Potentially interfering substances include, but are not limited to, anticoagulated whole blood with ACD, EDTA, Heparin, and Sodium Citrate, human plasma, three blood culture media bottles (Becton Dickinson BACTEC™ Plus Aerobic/F, BioMérieux BacT/ALERT SA (Standard Aerobic), and TREK Diagnostics VersaTREK REDOXI (Aerobic), bilirubin, y-globulin, hemoglobin, triglycerides, and sodium polyanetholesulfonate (SPS). Bilirubin, y-globulin, hemoglobin, and triglycerides were tested at concentrations approximately one log higher than reference levels. SPS was tested at a 10 fold higher concentration than found in blood culture media. Negative samples (n=8) were tested in each substance to determine the effect on the performance of the sample processing control (SPC). Positive samples (n=8) were tested per substance with two clinical isolates each of MSSA (29213 and 102-04) and MRSA (SCCmec types II and HII) spiked near the analytical LoD determined for each isolate. All results were compared to positive and negative buffer controls. All negative specimens were correctly reported "MRSA NEGATIVE; SA NEGATIVE" using the Xpert MRSA/SA Blood Culture Assay. None of the
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potentially interfering substances had a statistically significant inhibitory effect on SPC performance in negative samples (p-value =>0.05). All of the positive MSSA specimens were correctly reported "MRSA NEGATIVE; SA POSITIVE" using the Xpert MRSA/SA Blood Culture Assay. All of the positive MRSA specimens were correctly reported "MRSA POSITIVE: SA POSITIVE" using the Xpert MRSA/SA Blood Culture Assay. None of the potentially interfering substances resulted in a Ct difference of ≥1 cycle relative to the buffer controls and no false-negative results were reported.
## Clinical Studies
## Clinical Comparison Study
· Performance characteristics of the Xpert MRSA/SA Blood Culture Assay were determined in a multi-site prospective study at eight US institutions by comparing the Xpert MRSA/SA Blood Culture Assay with culture.
Subjects included individuals whose routine care called for blood culture testing. If the blood culture sample was positive for microbial growth and the Gram stain showed Gram positive cocci (singles or in clusters), the sample was eligible for inclusion in the clinical study, and aliquots of leftover culture material were obtained for testing by the Xpert MRSA/SA Blood Culture Assay. Culture and Gram stain procedures, and patient management continued at the sites per the standard practice. Susceptibility testing was performed in accordance with the CLSI documents M2-A11 and M100-S22. Cefoxitin disc was used as a surrogate for detecting methicillin/oxacillin resistance.
Performance of the Xpert MRSA/SA Blood Culture Assay was calculated relative to the reference culture results.
### Overall Results
A total of 792 specimens were tested for MRSA and SA by Xpert MRSA/SA Blood Culture Assay and culture.
The Xpert MRSA/SA Blood Culture Assay identified 98.1% of the specimens positive for MRSA and 99.6% of the specimens negative for MRSA relative to culture.
The Xpert MRSA/SA Blood Culture Assay identified 99.6% of the specimens positive for SA and 99.5% of the specimens negative for SA relative to the reference culture method. The performance of the Xpert MRSA/SA Blood Culture Assay is summarized in Table 5.4.
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| | | Culture | | | |
|-------------------|-------------------------------------------------------------------------------------|---------|-----------|------------------|-------|
| | | MRSA+ | SA+/MRSA- | Neg/No<br>Growth | Total |
| Xpert | MRSA+ | 103 | 2 | 1 | 106 |
| | SA+/MRSA- | 2 | 128 | 2 | 132 |
| | SA- | 0 | 1 | 553 | 554 |
| | Total | 105 | 131 | 556 | 792 |
| Xpert Performance | MRSA:<br>PPA: 98.1% (103/105, 95% CI: 93.3-99.8) | | | | |
| | NPA: 99.6% (684/687, 95% CI: 98.7-99.9 ) | | | | |
| | SA: | | | | |
| | PPA: 99.6% (235/236, 95% CI: 97.7-99.9 )<br>NPA: 99.5% (553/556, 95% CI: 98.4-99.9) | | | | |
Table 5.4. MRSA/SA Performance vs. Reference Culture
Of the Xpert MRSA/SA Blood Culture Assay runs on eligible specimens, 96.1% (764/795) were successful on the first attempt. The remaining 31runs gave indeterminate results on the first attempt (1 "INVALID", 22 "ERROR" and 8 "NO RESULT"). Thirty of the 31 indeterminate cases were retested; one specimen was not retested. Twenty-eight of the 30 indeterminate cases that were retested yielded valid results upon repeat assay. The overall rate of assay success was 99.6% (792/795).
## Reproducibility Study
Reproducibility of the Xpert MRSA/SA Assay was evaluated at three sites using samples comprised of cultured material spiked into a simulated matrix. The samples were prepared at concentration levels representing high negative (below LoD), low positive (~1 X LoD) and moderate positive (~2-3X LoD) for both MRSA and MSSA. Two different strains of MRSA were used. Negative panel members were also included and were comprised of Staphylococcus epidermidis spiked into a simulated matrix. A panel of 11 samples was tested on five different days by two different operators three times per day at three sites (11 samples x 2 operators x 5 days x 3 replicates per day x 3 sites). One lot of Xpert MRSA/SA reagents was included in the study. Xpert MRSA/SA Assays were performed according to the Xpert MRSA/SA Assay procedure. The rate of agreement for each panel member is presented in Table 5.5.
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| Sample | Site 1/<br>GX Dx | Site 2/<br>Inf-80 | Site 3/<br>Inf-48 | % Total Agreement |
|-----------------------------|-------------------|-------------------|-------------------|--------------------|
| MRSA-1 high neg (below LOD) | 56.7%<br>(17/30) | 60.0%<br>(18/30) | 66.7%<br>(20/30) | 61.1%<br>(55/90) |
| MRSA-1 low pos (~1X LOD) | 100.0%<br>(30/30) | 100.0%<br>(30/30) | 100.0%<br>(30/30) | 100.0%<br>(90/90) |
| MRSA-1 mod pos (~2-3X LOD) | 100.0%<br>(30/30) | 100.0%<br>(30/30) | 100.0%<br>(29/29) | 100.0%<br>(89/89)a |
| MRSA-2 high neg (below LOD) | 43.3%<br>(13/30) | 53.3%<br>(16/30) | 70.0%<br>(21/30) | 55.6%<br>(50/90) |
| MRSA-2 low pos (~1X LOD) | 100.0%<br>(30/30) | 100.0%<br>(30/30) | 100.0%<br>(30/30) | 100.0%<br>(90/90) |
| MRSA-2 mod pos (~2-3X LOD) | 100.0%<br>(30/30) | 100.0%<br>(30/30) | 100.0%<br>(30/30) | 100.0%<br>(90/90) |
| MSSA high neg (below LOD) | 60.0%<br>(18/30) | 48.3%<br>(14/29) | 70.0%<br>(21/30) | 59.6%<br>(53/89)b |
| MSSA low pos (~1X LOD) | 96.7%<br>(29/30) | 100.0%<br>(30/30) | 96.7%<br>(29/30) | 97.8%<br>(88/90) |
| MSSA mod pos (~2-3X LOD) | 100.0%<br>(30/30) | 100.0%<br>(30/30) | 100.0%<br>(30/30) | 100.0%<br>(90/90) |
| Negative-1 | 100%<br>(30/30) | 100%<br>(30/30) | 100%<br>(30/30) | 100%<br>(90/90) |
| Negative-2 | 100%<br>(30/30) | 100%<br>(30/30) | 100%<br>(30/30) | 100%<br>(90/90) |
Table 5.5. Summary of Reproducibility Results - Agreement by Study Site/Instrument
"One sample indeterminate after initial and retest.
One sample mistakenly not run.
The reproducibility of the Xpert MRSA/SA Assay was also evaluated in terms of the fluorescence signal expressed in cycle threshold (Ct) values for each target detected. The mean, standard deviation (SD), and coefficient of variation (CV) between-sites, betweenlots, between-days, and between-runs for each panel member are presented in Table 5.6.
{11}------------------------------------------------
| Table 5.6. Summary of Reproducibility Data | | | | | | | | | | | | | | | |
|--------------------------------------------|--------|----------|---------|--------------|------------|------------------------|-----------|-----------------|-----------|------------------|------------|------|-----------|------|-----------|
| Target | Sample | Conc | Agree/N | Agrmt<br>(%) | Mean<br>Ct | Between-<br>Instrument | | Between-<br>Day | | Between-<br>Run1 | Within-Run | | Total | | |
| | | | | | | SD | CV<br>(%) | SD | CV<br>(%) | SD | CV<br>(%) | SD | CV<br>(%) | SD | CV<br>(%) |
| spa | MRSA-1 | high neg | 55/90 | 61.1 | 35.6 | 0.18 | 0.5 | 0.21 | 0.6 | 0.00 | 0.0 | 0.95 | 2.7 | 0.99 | 2.8 |
| | MRSA-1 | low pos | 90/90 | 100.0 | 32.8 | 0.27 | 0.8 | 0.00 | 0.0 | 0.00 | 0.0 | 0.62 | 1.9 | 0.67 | 2.1 |
| | MRSA-1 | mod pos | 89/89 | 100.0 | 31.2 | 0.11 | 0.4 | 0.00 | 0.0 | 0.00 | 0.0 | 0.58 | 1.9 | 0.59 | 1.9 |
| | MRSA-2 | high neg | 50/90 | 55.6 | 35.3 | 0.15 | 0.4 | 0.00 | 0.0 | 0.00 | 0.0 | 0.99 | 2.8 | 1.00 | 2.8 |
| | MRSA-2 | low pos | 90/90 | 100.0 | 32.3 | 0.11 | 0.4 | 0.00 | 0.0 | 0.13 | 0.4 | 0.63 | 1.9 | 0.65 | 2.0 |
| | MRSA-2 | mod pos | 90/90 | 100.0 | 30.7 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.55 | 1.8 | 0.55 | 1.8 |
| | MSSA | high neg | 53/89 | 59.6 | 36.3 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 1.26 | 3.5 | 1.26 | 3.5 |
| | MSSA | low pos | 88/90 | 97.8 | 33.5 | 0.07 | 0.2 | 0.18 | 0.5 | 0.00 | 0.0 | 0.89 | 2.7 | 0.91 | 2.7 |
| | MSSA | mod pos | 90/90 | 100.0 | 31.7 | 0.08 | 0.2 | 0.20 | 0.6 | 0.17 | 0.6 | 0.48 | 1.5 | 0.56 | 1.8 |
| | NEG-1 | Neg | 90/90 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | NEG-2 | Neg | 90/90 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| mec | MRSA-1 | high neg | 55/90 | 61.1 | 35.8 | 0.00 | 0.0 | 0.36 | 1.0 | 0.00 | 0.0 | 0.83 | 2.3 | 0.91 | 2.5 |
| | MRSA-1 | low pos | 90/90 | 100.0 | 33.4 | 0.12 | 0.4 | 0.19 | 0.6 | 0.00 | 0.0 | 0.55 | 1.6 | 0.59 | 1.8 |
| | MRSA-1 | mod pos | 89/89 | 100.0 | 31.9 | 0.08 | 0.2 | 0.00 | 0.0 | 0.00 | 0.0 | 0.46 | 1.4 | 0.47 | 1.5 |
| | MRSA-2 | high neg | 50/90 | 55.6 | 35.8 | 0.00 | 0.0 | 0.34 | 0.9 | 0.00 | 0.0 | 1.03 | 2.9 | 1.08 | 3.0 |
| | MRSA-2 | low pos | 90/90 | 100.0 | 32.8 | 0.11 | 0.3 | 0.00 | 0.0 | 0.16 | 0.5 | 0.51 | 1.6 | 0.54 | 1.7 |
| | MRSA-2 | mod pos | 90/90 | 100.0 | 31.5 | 0.00 | 0.0 | 0.16 | 0.5 | 0.00 | 0.0 | 0.49 | 1.5 | 0.51 | 1.6 |
| | MSSA | high neg | 53/89 | 59.6 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | MSSA | low pos | 88/90 | 97.8 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | MSSA | mod pos | 90/90 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | NEG-1 | Neg | 90/90 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | NEG-2 | Neg | 90/90 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| SCC | MRSA-1 | high neg | 55/90 | 61.1 | 37.2 | 0.20 | 0.5 | 0.37 | 1.0 | 0.35 | 1.0 | 0.82 | 2.2 | 0.98 | 2.6 |
| | MRSA-1 | low pos | 90/90 | 100.0 | 34.5 | 0.19 | 0.5 | 0.23 | 0.7 | 0.00 | 0.0 | 0.59 | 1.7 | 0.66 | 1.9 |
| | MRSA-1 | mod pos | 89/89 | 100.0 | 33.0 | 0.16 | 0.5 | 0.00 | 0.0 | 0.00 | 0.0 | 0.45 | 1.4 | 0.48 | 1.5 |
| | MRSA-2 | high neg | 50/90 | 55.6 | 36.8 | 0.23 | 0.6 | 0.24 | 0.6 | 0.10 | 0.3 | 1.00 | 2.7 | 1.06 | 2.9 |
| | MRSA-2 | low pos | 90/90 | 100.0 | 33.7 | 0.11 | 0.3 | 0.00 | 0.0 | 0.26 | 0.8 | 0.57 | 1.7 | 0.64 | 1.9 |
| | MRSA-2 | mod pos | 90/90 | 100.0 | 32.4 | 0.00 | 0.0 | 0.09 | 0.3 | 0.00 | 0.0 | 0.45 | 1.4 | 0.46 | 1.4 |
| | MSSA | high neg | 53/89 | 59.6 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | MSSA | low pos | 88/90 | 97.8 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | MSSA | mod pos | 90/90 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | NEG-1 | Neg | 90/90 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | NEG-2 | Neg | 90/90 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| SPC | MRSA-1 | high neg | 55/90 | 61.1 | 32.7 | 0.00 | 0.0 | 0.00 | 0.0 | 0.20 | 0.6 | 0.65 | 2.0 | 0.68 | 2.1 |
| | MRSA-1 | low pos | 90/90 | 100.0 | 33.0 | 0.00 | 0.0 | 0.16 | 0.5 | 0.10 | 0.3 | 0.61 | 1.8 | 0.63 | 1.9 |
| | MRSA-1 | mod pos | 89/89 | 100.0 | 33.0 | 0.27 | 0.8 | 0.00 | 0.0 | 0.00 | 0.0 | 0.83 | 2.5 | 0.87 | 2.6 |
| | MRSA-2 | high neg | 50/90 | 55.6 | 33.1 | 0.23 | 0.7 | 0.00 | 0.0 | 0.10 | 0.3 | 0.85 | 2.6 | 0.89 | 2.7 |
| | MRSA-2 | low pos | 90/90 | 100.0 | 32.9 | 0.15 | 0.5 | 0.00 | 0.0 | 0.00 | 0.0 | 0.78 | 2.4 | 0.79 | 2.4 |
| | MRSA-2 | mod pos | 90/90 | 100.0 | 32.8 | 0.00 | 0.0 | 0.23 | 0.7 | 0.00 | 0.0 | 0.66 | 2.0 | 0.70 | 2.1 |
| | MSSA | high neg | 53/89 | 59.6 | 32.8 | 0.18 | 0.5 | 0.15 | 0.5 | 0.00 | 0.0 | 0.74 | 2.2 | 0.77 | 2.4 |
| | MSSA | low pos | 88/90 | 97.8 | 32.9 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.72 | 2.2 | 0.72 | 2.2 |
| | MSSA | mod pos | 90/90 | 100.0 | 33.0 | 0.00 | 0.0 | 0.31 | 0.9 | 0.00 | 0.0 | 0.69 | 2.1 | 0.76 | 2.3 |
| | NEG-1 | Neg | 90/90 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | NEG-2 | Neg | 90/90 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
Summary of Reproducibility Data Table 56
Agreement, Conc-concentration, CV=coefficient of variation, NA=Not Applicable for negative samples, SD=standard deviation Note: The variance estimate from some ically negative, which can occur if the variability due to those factors is very small. When this occurs, the variability as measured with SD and CV is set to 0.
1 A run is defined as the three samples per panel member run by one operator at one site on one day.
## Instrument System Precision Study
An in-house precision study was conducted to compare the performance of the GeneXpert Dx, the Infinity-48 and the Infinity-80 Instrument Systems using samples comprised of cultured material spiked into a simulated matrix. The samples were prepared at concentration levels representing high negative (below LoD), low positive (~1X LoD) and moderate positive (~2-3X LoD) for both MRSA and MSSA. Two different strains of MRSA were used. Negative panel members were also included and were comprised of Staphylococcus epidermidis spiked into a
{12}------------------------------------------------
simulated matrix. A panel of 11 specimens was tested on 12 different days by two different operators four times per day per instrument (11 specimens x 12 days x 4 replicates per day x 3 instruments). One lot of Xpert MRSA/SA reagents was included in the study. Xpert MRSA/SA Assays were performed according to the Xpert MRSA/SA Assay procedure. The rate of agreement for each panel member is presented in Table 5.7.
| Sample | GX Dx | Inf-48 | Inf-80 | % Total Agreement |
|-----------------------------|-------------------|-------------------|-------------------|---------------------|
| MRSA-1 high neg (below LOD) | 50.0%<br>(48/96) | 51.6%<br>(49/95) | 35.4%<br>(34/96) | 45.6%<br>(131/287)a |
| MRSA-1 low pos (~1X LOD) | 96.9%<br>(93/96) | 99.0%<br>(95/96) | 99.0%<br>(95/96) | 98.3%<br>(283/288) |
| MRSA-1 mod pos (~2-3X LOD) | 100.0%<br>(96/96) | 100.0%<br>(96/96) | 99.0%<br>(95/96) | 99.7%<br>(287/288) |
| MRSA-2 high neg (below LOD) | 80.2%<br>(77/96) | 78.1%<br>(75/96) | 80.2%<br>(77/96) | 79.5%<br>(229/288) |
| MRSA-2 low pos (~1X LOD) | 100.0%<br>(96/96) | 100.0%<br>(96/96) | 100.0%<br>(96/96) | 100.0%<br>(288/288) |
| MRSA-2 mod pos (~2-3X LOD) | 100.0%<br>(96/96) | 100.0%<br>(96/96) | 99.0%<br>(95/96) | 99.7%<br>(287/288) |
| MSSA high neg (below LOD) | 76.0%<br>(73/96) | 71.9%<br>(69/96) | 81.3%<br>(78/96) | 76.4%<br>(220/288) |
| MSSA low pos (~1X LOD) | 96.9%<br>(93/96) | 99.0%<br>(95/96) | 100.0%<br>(96/96) | 98.6%<br>(284/288) |
| MSSA mod pos (~2-3X LOD) | 100.0%<br>(96/96) | 100.0%<br>(96/96) | 100.0%<br>(96/96) | 100.0%<br>(288/288) |
| Negative-1 | 100.0%<br>(96/96) | 100.0%<br>(96/96) | 100.0%<br>(96/96) | 100.0%<br>(288/288) |
| Negative-2 | 100.0%<br>(96/96) | 100.0%<br>(96/96) | 100.0%<br>(96/96) | 100.0%<br>(288/288) |
Table 5.7: Summary of Precision Results - Agreement by Instrument
One sample was indeterminate after initial and retest.
The precision study results were 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-instruments, between-days, and between-runs for each panel member are presented in Table 5.8.
{13}------------------------------------------------
| | | | | Tamle 3.0. Outlimary of I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 | | | | | | | | | | | |
|--------|--------|----------|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------|------------|------|----------|-----|----------|-----|------------|-------|---------|------|
| Target | Sample | Сопс | Agree/N | Agrmt<br>(%) | Mean<br>Ct | Between- | | Between- | | Between- | | Within-Run | | Total | |
| | | | | | | Instrument | | Day | | Run' | | | | | |
| | | | | | | SD | CV | SD | CV | SD | CV | SD | CV | SD | CV |
| | | | | | | | (%) | | (%) | | (%) | | (%) | | (%) |
| spa | MRSA-I | high neg | 131/287 | 45.6 | 34.4 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 1.09 | 3.2 | 1.09 | 3.2 |
| | MRSA-I | low pos | 283/288 | 98.3 | 32.9 | 0.02 | 0.1 | 0.16 | 0.5 | 0.00 | 0.0 | 0.78 | 2.4 | 0.80 | 2.4 |
| | MRSA-1 | mod pos | 287/288 | 99.7 | 32.0 | 0.06 | 0.2 | 0.10 | 0.3 | 0.00 | 0.0 | 0.62 | 1.9 | 0.63 | 2.0 |
| | MRSA-2 | high neg | 229/288 | 79.5 | 36.2 | 0.14 | 0.4 | 0.00 | 0.0 | 0.00 | 0.0 | 1.19 | 3.3 | 1.35 | 3.7 |
| | MRSA-2 | low pos | 288/288 | 100.0 | 32.4 | 0.03 | 0.1 | 0.00 | 0.0 | 0.00 | 0.0 | 0.57 | 1.8 | 0.62 | 1.9 |
| | MRSA-2 | mod pos | 287/288 | 99.7 | 31,1 | 0.12 | 0.4 | 0.00 | 0.0 | 0.00 | 0.0 | 0.49 | 1.6 | 0.21 | 1.7 |
| | MSSA | high neg | 220/288 | 76.4 | 36.4 | 0.2 1 | 0.6 | 0.00 | 0.0 | 0.00 | 0.0 | 1.36 | 3.7 | । 'ਤੇਖੋ | 4.4 |
| | MSSA | low pos | 284/288 | 98.6 | 33.8 | 0.09 | 0.3 | 0.18 | 0:5 | 0.00 | 0.0 | 0.87 | 2.6 | 0.90 | 2.7 |
| | MSSA | mod pos | 288/288 | 100.0 | 32.2 | 0.08 | 0.3 | 0.00 | 0.0 | 0.00 | 0.0 | 0.70 | 2.2 | 0.74 | 2.3 |
| | NEG-I | Neg | 288/288 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | NEG-2 | Neg | 288/288 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | MRSA-I | high neg | 131/287 | 45.6 | 34.5 | 0.00 | 0.0 | 0.11 | 0.3 | 0.00 | 0.0 | 0.86 | 2.5 | 0.87 | 2.5 |
| mec | MRSA-I | low pos | 283/288 | 98.3 | 33.4 | 0.07 | 0.2 | 0.14 | 0.4 | 0.00 | 0.0 | 0.61 | 1.8 | 0.63 | 1.9 |
| | MRSA-I | mod pos | 287/288 | 99.7 | 32.5 | 0.08 | 0.2 | 0.00 | 0.0 | 0.00 | 0.0 | 0.55 | 1.7 | 0.56 | 1.7 |
| | MRSA-2 | high neg | 229/288 | 79.5 | 35.9 | 0.00 | 0.0 | 0.28 | 0.8 | 0.00 | 0.0 | 1.02 | 2.8 | 1 .06 | 2.9 |
| | MRSA-2 | low pos | 288/288 | 100.0 | 32.8 | 0.06 | 0.2 | 0.00 | 0.0 | 0.00 | 0.0 | 0.49 | ાં .ડ | 0.53 | 1.6 |
| | MRSA-2 | mod pos | 287/288 | 99.7 | 31.5 | 0.14 | 0. ર | 0.05 | 0.2 | 0.00 | 0.0 | 0.45 | 1.4 | 0.47 | રે |
| | MSSA | high neg | 220/288 | 76.4 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | MSSA | low pos | 284/288 | 98.6 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | MSSA | mod pos | 288/288 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | NEG-I | Neg | 288/288 | 1 00.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | NEG-2 | Neg | 288/288 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | MRSA-1 | high neg | 131/287 | 45.6 | 36.7 | 0.18 | 0.5 | 0.00 | 0.0 | 0.00 | 0.0 | 1 .5 l | 4.1 | 1.52 | 4.1 |
| | MRSA-I | low pos | 283/288 | 98.3 | 34.7 | 0.00 | 0.0 | 0.20 | 0.6 | 0.00 | 0.0 | 1.11 | 3.2 | 1,13 | 3.2 |
| SCC | MRSA-1 | mod pos | 287/288 | 99.7 | 33.7 | 0.12 | 0.3 | 0.00 | 0.0 | 0.00 | 0.0 | 0.78 | 2.3 | 0.78 | 2.3 |
| | MRSA-2 | high neg | 229/288 | 79.5 | 37.3 | 0.00 | 0.0 | 0.32 | 0.8 | 0.00 | 0.0 | 1.03 | 2.8 | 1.17 | 3.1 |
| | MRSA-2 | low pos | 288/288 | 1 00.0 | 34.2 | 0.02 | 0.1 | 0.00 | 0.0 | 0.00 | 0.0 | 0.44 | 1.3 | 0.50 | । .ડ |
| | MRSA-2 | mod pos | 287/288 | 99.7 | 33.0 | 0.12 | 0.4 | 0.03 | 0.1 | 0.00 | 0.0 | 0.49 | 1.5 | 0.50 | 1.5 |
| | MSSA | high neg | 220/288 | 76.4 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | MSSA | low pos | 284/288 | ૭૪.6 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | MSSA | mod pos | 288/288 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | NEG-1 | Neg | 288/288 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| | NEG-2 | Neg | 288/288 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| SPC | MRSA-1 | high neg | 131/287 | 45.6 | 33.4 | 0.00 | 0.0 | 0.17 | 0.5 | 0.00 | 0.0 | 0.84 | 2.5 | 0.86 | 2.6 |
| | MRSA-I | low pos | 283/288 | 98.3 | 33.4 | 0.10 | 0.3 | 0.21 | 0.6 | 0.00 | 0.0 | 0.77 | 2.3 | 0.80 | 2.4 |
| | MRSA-1 | mod pos | 287/288 | 99.7 | 33.4 | 0.08 | 0.2 | 0.15 | 0.5 | 0.00 | 0.0 | 0.72 | 2.2 | 0.74 | 2.2 |
| | MRSA-2 | high neg | 229/288 | 79.5 | 33.4 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.82 | 2.4 | 0.82 | 2.4 |
| | MRSA-2 | low pos | 288/288 | 100.0 | 33.4 | 0.02 | 0. I | 0.00 | 0.0 | 0.00 | 0.0 | 0.73 | 2.2 | 0.77 | 2.3 |
| | MRSA-2 | mod pos | 287/288 | 99.7 | 33.3 | 0.00 | 0.0 | 0.09 | 0.3 | 0.00 | 0.0 | 0.74 | 2.2 | 0.75 | 2.2 |
| | MSSA | high neg | 220/288 | 76.4 | 33.4 | 0.00 | 0.0 | 0.20 | 0.6 | 0.00 | 0.0 | 0.83 | 2.5 | 0.85 | 2.6 |
| | MSSA | low pos | 284/288 | 98.6 | 33.5 | 0.00 | 0.0 | 0.00 | 0.0 | 0.00 | 0.0 | 0.86 | 2.6 | 0.87 | 2.6 |
| | MSSA | mod pos | 288/288 | 100.0 | 33.1 | 0.11 | 0.3 | 0.00 | 0.0 | 0.00 | 0.0 | 0.75 | 2.2 | 0.77 | 2.3 |
| | NEG-1 | Neg | 288/288 | 100.0 | 33.4 | 0.00 | 0.0 | 0.13 | 0.4 | 0.00 | 0.0 | 0.85 | 2.6 | 0.87 | 2.6 |
| | NEG-2 | Neg | 288/288 | 100.0 | 33.5 | 0.00 | 0.0 | 0.02 | 0.1 | 0.00 | 0.0 | 0.84 | 2.5 | 0.84 | 2.5 |
Table 58. Summary of Precision Data
Agrow=Agreement, Conc=concentration, CV=coefficient of variation, N/A=Not Applicable for negative samples, SD=standard deviation
Note: The variance estimate from some factors may be numerically negative, which can occur if the variability due to those factors is very small. When this occurs, the variability as measured with SD and CV is set to 0.
I A run is defined as the four samples per panel member run by one operator at one site on one day.
## Conclusions
The results of the nonclinical analytical and clinical performance studies summarized above demonstrate that the Xpert MRSA/SA Blood Culture Assay is substantially equivalent to the predicate devices.
{14}------------------------------------------------
Image /page/14/Picture/0 description: The image shows the logo for the U.S. Department of Health and Human Services. The logo is a circular seal with the words "DEPARTMENT OF HEALTH & HUMAN SERVICES - USA" around the perimeter. Inside the circle is an emblem of an eagle with three lines representing the bird's body and wings.
#### DEPARTMENT OF HEALTH & HUMAN SERVICES
Public Health Service
Food and Drug Administration 10903 New Hampshire Avenue Document Control Center - WO66-G60 Silver Spring, MD 20993-0002
RAINER ZIERMANN, PH.D. VICE PRESIDENT, CLINICAL AFFAIRS CEPHEID 904 CARRIBEAN DRIVE SUNNYVALE CA 94089
June 20, 2013
Re: K130894
Trade/Device Name: Xpert MRSA/SA Blood Culture Assay Regulation Number: 21 CFR 866.1640 Regulation Name: Antimicrobial susceptibility test powder Regulatory Class: II Product Code: NOX Dated: March 29, 2013 Received: April 02, 2013
Dear Dr. Ziermann:
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 (QS) regulation (21 CFR Part 820); and if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050. .
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Page 2-Dr. Ziermann
If you desire specific advice for your device on our labeling regulations (2) CFR Parts 801 and 809), please contact the Division of Small Manufacturers, International and Consumer Assistance 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. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21CFR 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 Small Manufacturers, International and Consumer Assistance 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,
Uwe Scherf - S for
Sally A. Hojvat, M.Sc., Ph.D. Director, Division of Microbiology Devices Office of In Vitro Diagnostics and Radiological Health Center for Devices and Radiological Health
Enclosure
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#### Indications for Use ·4.0
### Indications for Use Form
510(k) Number (if known): k130894
Device Name: Xpert® MRSA/SA Blood Culture Assay
Indications for Use:
The Cepheid Xpert® MRSA/SA Blood Culture Assay, performed on the GeneXpert® Instrument Systems, is a qualitative in vitro diagnostic test intended for the detection of Staphylococcus aureus (SA) and methicillin-resistant Staphylococcus aureus (MRSA) DNA directly from positive blood cultures. The assay utilizes automated real-time polymerase chain reaction (PCR) for the amplification of MRSA/SA specific DNA targets and fluorogenic target-specific hybridization probes for the real-time detection of the amplified DNA. The assay is performed directly on positive blood culture samples from BD BACTEC™ Plus Aerobic/F, BacT/ALERT® SA (Standard Aerobic) or VersaTREK REDOX 1® (aerobic) blood culture bottles that are determined by Gram stain as Gram Positive Cocci in Clusters (GPCC) or as Gram Positive Cocci in singles (GPC). The Xpert MRSA/SA Blood Culture Assay is indicated for use in conjunction with other laboratory tests, such as culture, and clinical data available to the clinician as an aid in the detection of MRSA/SA from positive blood cultures. Subculturing of positive blood cultures is necessary to recover organisms for susceptibility testing or for epidemiological typing. The Cepheid Xpert MRSA/SA Blood Culture Assay is not intended to monitor treatment for MRSA/SA infections.
| Prescription Use _X_ | AND/OR | Over-The-Counter Use |
|-----------------------------|--------|------------------------|
| (Part 21 CFR 801 Subpart D) | | (21 CFR 801 Subpart C) |
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Concurrence of CDRH, Office of In Vitro Diagnostic Devices (OI…
