The Cepheid® Xpert Flu Assay is an automated, multiplex real-time RT-PCR assay intended for the in vitro qualitative detection and differentiation of influenza B and 2009 H1N1 influenza viral RNA. The Xpert Flu Assay uses nasal aspirates/washes and nasopharyngeal swab specimens collected from patients with signs and symptoms of respiratory infection in conjunction with clinical and epidemiological risk factors. The Xpert Flu Assay is intended as an aid in the diagnosis of influenza.

Negative results do not preclude influenza virus infection and should not be used as the sole basis for treatment or other patient management decisions.

Performance characteristics for influenza A were established during the 2009-2010 influenza season when 2009 H1N1 influenza was the predominant influenza A virus in circulation. When other influenza A viruses are emerging, performance characteristics may vary.

If infection with a novel influenza A virus is suspected based on current clinical and epidemiological screening criteria recommended by public health authorities, specimens should be collected with appropriate infection control precautions for novel virulent influenza viruses and sent to state or local health department for testing. Viral culture should not be attempted in these cases unless a BSL 3+ facility is available to receive and culture specimens.

Device Description

The Xpert Flu Assay is a rapid, automated in vitro diagnostic test for qualitative detection and differentiation of influenza A, influenza B and influenza A, subtype 2009 HINI. The assay is performed on the Cepheid GeneXpert Instrument Systems. The GeneXpert Instrument Systems automate and integrate sample purification, nucleic acid amplification, and detection of the target sequence in simple or complex samples using real-time PCR and RT-PCR assays. The 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 and specimens never come into contact with working parts of the instrument modules, cross-contamination between samples is eliminated.

The Xpert Flu Assay includes reagents for the detection and differentiation of influenza A, influenza B and influenza A, subtype 2009 H1N1 directly from nasal aspirates/washes (NA/W) and nasopharyngeal (NP) swab specimens from patients with signs and symptoms of respiratory infection. A Sample Processing Control (SPC) and a Probe Check Control (PCC) are also included. The SPC is present to control for adequate processing of the target viruses and to monitor the presence of inhibitors in the PCR reaction. The Probe Check Control (PCC) verifies reagent rehydration, PCR tube filling in the cartridge, probe integrity and dye stability.

The liquid specimen (NA/W) or swab specimen (NP) is collected according to the institution's standard procedures and placed into Universal Transport Medium (3mL UTM tubes). Following a brief mixing by inverting the UTM tube five times, the eluted material and one single-use reagent (Reagent 1), that is provided with the assay, are transferred to different, uniquely-labeled chambers of the disposable fluidic cartridge (the Xpert Flu cartridge). The user initiates a test from the system user interface and places the cartridge into the GeneXpert instrument platform, which performs hands-off reverse transcription and real-time, multiplex polymerase chain reaction (PCR) for detection of DNA. In this platform, additional sample preparation, amplification, and real-time detection are all fully-automated and completely integrated.

The single-use, multi-chambered fluidic cartridges are designed to complete sample preparation and real-time RT-PCR for detection and differentiation of influenza A, influenza B and influenza A, subtype 2009 H1N1 in 75 minutes. The GeneXpert Instrument Systems have 1 to 48 randomly accessible modules 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.

AI/ML Overview

Acceptance Criteria and Device Performance Study for Xpert Flu Assay

This report details the acceptance criteria and the study proving the Cepheid Xpert Flu Assay meets these criteria, based on the provided 510(k) summary (K103766).

1. Table of Acceptance Criteria and Reported Device Performance

The 510(k) summary does not explicitly state pre-defined quantitative acceptance criteria for sensitivity and specificity. Instead, the clinical study results are presented as the "performance characteristics" and are compared against a reference method. It's implied that achieving high agreement with the reference method across various influenza types and specimen types constitutes acceptable performance for substantial equivalence.

Based on the clinical performance study, the device performance is reported as follows:

Clinical Performance on Prospective Nasal Aspirates/Washes (NA/W)

Target	Performance Measure	Acceptance/Reference Method Performance
Influenza A	Sensitivity	85.7% (95% CI: 42.1-99.6)
	Specificity	99.1% (95% CI: 97.4-99.8)
2009 H1N1	Sensitivity	100% (95% CI: 39.8-100)
	Specificity	98.8% (95% CI: 97.0-99.7)
Influenza B	Sensitivity	100% (95% CI: 65.2-100)
	Specificity	99.4% (95% CI: 98.1-99.9)

Clinical Performance on Prospective Nasopharyngeal (NP) Swabs

Target	Performance Measure	Acceptance/Reference Method Performance
Influenza A	Sensitivity	100% (95% CI: 59.0-100)
	Specificity	98.3% (95% CI: 96.0-99.4)
2009 H1N1	Sensitivity	100% (95% CI: 47.8-100)
	Specificity	99.0% (95% CI: 97.0-99.8)
Influenza B	Sensitivity	87.5% (95% CI: 47.3-99.7)
	Specificity	99.7% (95% CI: 98.1-100)

Clinical Performance on Archived NA/W Specimens (vs. FDA Cleared Molecular Comparator)

Target	Performance Measure	Accepatance/Reference Method Performance
Influenza A	Positive Agreement	99.4% (95% CI: 96.6-100)
	Negative Agreement	100% (95% CI: 98.6-100)
2009 H1N1	Positive Agreement	98.4% (95% CI: 94.4-99.8)
	Negative Agreement	99.7% (95% CI: 98.1-100)
Influenza B	Positive Agreement	100% (95% CI: 91.2-100)
	Negative Agreement	100% (95% CI: 99.0-100)

Clinical Performance on Archived NP Swabs (vs. Viral Culture + DFA)

Target	Performance Measure	Acceptance/Reference Method Performance
Influenza A	Positive Agreement	97.5% (95% CI: 92.7-99.5)
	Negative Agreement	100% (95% CI: 89.1-100)
2009 H1N1	Positive Agreement	100% (95% CI: 95.7-100)
	Negative Agreement	100% (95% CI: 94.5-100)
Influenza B	Positive Agreement	93.8% (95% CI: 79.2-99.2)
	Negative Agreement	99.2% (95% CI: 95.4-100)

Clinical Performance on Archived NP Swabs (vs. FDA Cleared Molecular Comparator)

Target	Performance Measure	Acceptance/Reference Method Performance
Influenza A	Positive Agreement	98.1% (95% CI: 89.7-100)
	Negative Agreement	99.2% (95% CI: 95.5-100)
2009 H1N1	Positive Agreement	100% (95% CI: 88.1-100)
	Negative Agreement	99.3% (95% CI: 96.2-100)
Influenza B	Positive Agreement	93.8% (95% CI: 69.8-99.8)
	Negative Agreement	100% (95% CI: 97.7-100)

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

Prospective Specimens:

NA/W specimens: 342
NP swab specimens: 297

Archived Specimens:

NA/W specimens: 425
NP swab specimens: 150 (compared to viral culture + DFA), 177 (compared to FDA cleared molecular assay)

Data Provenance: The clinical study was conducted at six institutions in the U.S. and Australia. The study included both prospective and archived specimens.

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

The document does not explicitly state the number of experts or their specific qualifications (e.g., radiologist with X years of experience) used to establish the ground truth. However, the ground truth for "viral culture followed by direct fluorescent assay (DFA)" is a standard laboratory method, implying trained laboratory personnel perform these tests, which typically require specific certifications and experience. Sequencing results for influenza A positive specimens were also used as part of the ground truth.

4. Adjudication Method for the Test Set

The concept of an "adjudication method" (like 2+1, 3+1) is typically associated with studies where multiple human readers interpret results, and disagreement is resolved by an adjudicator. This is not directly applicable to a molecular diagnostic assay where results are objectively determined by instrumentation.

The document describes sequencing being performed for all influenza A positive specimens (identified by viral culture/DFA or the FDA cleared molecular assay) to differentiate subtypes. This acts as a confirmatory "adjudication" step for influenza A subtyping.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done

No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done. This study is for a diagnostic assay, not an AI-assisted human reading task.

6. If a Standalone (i.e. algorithm only without human-in-the loop performance) was done

Yes, a standalone performance study was done. The Xpert Flu Assay is an automated, multiplex real-time RT-PCR assay intended for in vitro qualitative detection and differentiation of influenza viral RNA. The performance characteristics described in the "Clinical Performance Study" sections (Pgs. 14-21) are for the device (Xpert Flu Assay) operating independently, generating its own results. There is no human interpretation of imaging or other complex data involved in generating the primary test result from the assay itself.

7. The Type of Ground Truth Used

The ground truth used for the clinical performance study varied based on the specimen type and whether it was prospective or archived:

Prospective specimens: Viral culture followed by direct fluorescent assay (DFA) was the primary comparator. This is a recognized laboratory standard.
Archived specimens (where viral culture was not performed prior to freezing): An FDA cleared molecular assay was performed as the comparator assay.
For all influenza A positive specimens (from both prospective and archived sets): Sequencing was used to differentiate influenza A subtypes (e.g., 2009 H1N1 from other influenza A). This can be considered as a highly specific confirmatory method.

8. The Sample Size for the Training Set

The document describes analytical and clinical performance studies but does not detail a separate "training set" or its size for an algorithm development since this is a molecular diagnostic assay, not a machine learning model in the typical sense. The assay is based on predefined biological reactions and detection thresholds, not trainable parameters derived from a large dataset. The analytical studies (Analytical Sensitivity, LoD, Analytical Specificity) and reproducibility studies define the assay's fundamental performance characteristics.

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

As noted above, there isn't a traditional "training set" as understood in machine learning. The assay's design and operating parameters would have been established through extensive laboratory work and optimization, including:

Analytical Reactivity (Inclusivity): Testing against known influenza strains at specific concentrations (Table 5.2).
Limit of Detection (LoD): Empirically determined as the lowest concentration (TCID50/mL) where 19/20 or 20/20 replicates were positive (Tables 5.3-5.6).
Analytical Specificity (Exclusivity): Testing against potentially interfering viral, bacterial, and yeast strains at specified concentrations (Table 5.7).

These studies use well-defined, characterized strains and concentrations as their "ground truth" to ensure the assay performs as expected.

Summary

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K103766

510(k) Summary

As required by 21 CFR Section 807.92(c).

APR 2 1 2011

Submitted by:	Cepheid®904 Caribbean DriveSunnyvale, CA 90489Phone number: (408) 400-8460.Fax number: (408) 541-6439
Contact:	Russel K. Enns, Ph.D.
Date of Preparation:	April 22, 2011
Device:
Trade name:	Xpert® Flu
Common name:	Xpert Flu Assay
Type of Test:	Automated, multiplex real-time reverse transcription-polymerase chain reaction (rRT-PCR) assay intended for thein vitro qualitative detection and differentiation of influenzaA, influenza B and 2009 H1N1 influenza viral RNA.
Regulation number/Classification name:	866.3980/Respiratory viral panel multiplex nucleic acid assay
Product code:	OQW, OCC, OOI
ClassificationAdvisory Panel	Microbiology (83)
Predicate Devices:	K073029: ProFLU+™ Assay,Gen-Probe Prodesse, Inc.K100148: Simplexa™ Influenza A H1N1(2009),Focus Diagnostics, Inc.

Device Description:

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Device Intended Use:

Negative results do not preclude influenza virus infection and should not be used as the sole basis for treatment or other patient management decisions.

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Substantial Equivalence:

The Xpert Flu Assay is substantially equivalent to the following predicate assays:

K073029: ProFLU+TM Assay, Gen-Probe Prodesse, Inc. .
K100148: Simplexa™ Influenza A H1N1(2009), Focus Diagnostics, Inc. .

Similarities and differences between the Cepheid Xpert Flu Assay and the predicate devices are shown in Table 5.1.

A clinical study at six sites was conducted to compare Xpert Flu Assay performance to the standard of care, viral culture followed by direct fluorescent assay (DFA). Sequencing for all influenza A positive specimens. For archived specimens, where viral culture was not performed prior to freezing, a FDA cleared molecular assay was performed as the comparator assay followed by sequencing of all influenza A positive specimens.

Table 5.1: Comparison of Similarities and Differences of the Xpert Flu Assay with
the Predicate Devices

Item	DeviceCepheid Xpert Flu	Gen-Probe Prodesse,Inc. ProFLU+	PredicatesFocus SimplexaInfluenza A H1N1
510(k) No.	K103766	K073029	K100148
Regulation	866.3332 and 866.3980	866.3980	866.3332
Product Code	OQW, OCC, OOI	OCC	OQW
Device Class	II	II	II
Technology/Detection	Multiplex real time RT/PCR	Multiplex real timeRT/PCR	Multiplex real timeRT/PCR
Intended Use	An automated, multiplexreal-time RT-PCR assayintended for the in vitroqualitative detection anddifferentiation of influenzaA, influenza B and 2009H1N1 influenza viral RNA.The Xpert Flu Assay usesnasal aspirates/washes andnasopharyngeal swab	A multiplex Real TimeRT-PCR in vitrodiagnostic test for therapid and qualitativedetection anddiscrimination ofInfluenza A Virus,Influenza B Virus, andRespiratory SyncytialVirus (RSV) nucleic	For use on the 3MIntegrated Cycler as part ofthe Microfluidic MolecularSystem for the in vitroqualitative detection anddifferentiation of influenzaA and 2009 H1N1influenza viral RNA innasopharyngeal swabs(NPS), nasal swabs (NS),
	Device		Predicates
Item	Cepheid Xpert Flu	Gen-Probe Prodesse,Inc. ProFLU+\	Focus SimplexaInfluenza A H1N1
	specimens collected frompatients with signs andsymptoms of respiratoryinfection in conjunctionwith clinical andepidemiological risk factors.The Xpert Flu Assay isintended as an aid in thediagnosis of influenza.Negative results do notpreclude influenza virusinfection and should not beused as the sole basis fortreatment or other patientmanagement decisions.Performance characteristicsfor influenza A wereestablished during the 2009-2010 influenza season when2009 H1N1 influenza wasthe predominant influenzaA virus in circulation. Whenother influenza A virusesare emerging, performancecharacteristics may vary.If infection with a novelinfluenza A virus issuspected based on currentclinical and epidemiologicalscreening criteriarecommended by publichealth authorities,specimens should becollected with appropriateinfection controlprecautions for novelvirulent influenza virusesand sent to state or localhealth department fortesting. Viral culture shouldnot be attempted in thesecases unless a BSL 3+facility is available toreceive and culturespecimens.	acids isolated andpurified fromnasopharyngeal (NP)swab specimensobtained fromsymptomatic patients.This test is intended foruse to aid in thedifferential diagnosis ofInfluenza A, InfluenzaB and RSV2 viralinfections in humansand is not intended todetect Influenza C.A negative test ispresumptive and it isrecommended theseresults be confirmed bycell culture. Negativeresults do not precludeinfluenza or RSV virusinfection and shouldnot be used as the solebasis for treatment orother managementdecisions.	and nasopharyngealaspirates (NPA) fromhuman patients with signsand symptoms ofrespiratory infection inconjunction with clinicaland epidemiological riskfactors.Negative results do notpreclude influenza virusinfection and should not beused as the sole basis fortreatment or other patientmanagement decisions.Performance characteristicsfor influenza A wereestablished during the2009-2010 influenza seasonwhen 2009 H1N1 influenzawas the predominantinfluenza A virus incirculation. When otherInfluenza A viruses areemerging, performancecharacteristics may vary.If infection with a novelInfluenza A virus issuspected based on currentclinical andepidemiological screeningcriteria recommended bypublic health authorities,specimens should becollected with appropriateinfection controlprecautions for novelvirulent Influenza virusesand sent to state or localhealth department fortesting. Viral culture shouldnot be attempted in thesecases unless a BSL 3+facility is available toreceive and culturespecimens
	Device	Predicates
Item	Cepheid Xpert Flu	Gen-Probe Prodesse,Inc. ProFLU+\	Focus SimplexaInfluenza A H1N1
Indication for Use	Patients with signs andsymptoms of respiratoryinfection in conjunctionwith clinical andepidemiological risk factors.	Symptomatic patients	Patients with signs andsymptoms of respiratoryinfection in conjunctionwith clinical andepidemiological risk factors
Assay Targets	Influenza A,influenza B, and influenzaA, subtype 2009 H1N1	Influenza A, influenzaB. RespiratorySyncytial Virus Type Aand Type B	Influenza A/2009 H1N1 influenza
Specimen Types	Nasal aspirates/washes(NA/W) andNasopharyngeal (NP) swabs	NP swab	NP swab, Nasal Swab (NS)and nasopharyngealaspirates (NA/W)
TechnologicalPrinciples	RT/PCR	RT/PCR	RT/PCR
Nucleic AcidExtraction	Yes	Yes	Yes
ExtractionMethods	Sample preparationintegrated in GeneXpertCartridge and GeneXpertInstrumentation System	Roche MagNA PureLC Total NA IsolationKit	Roche MagNA Pure LCTotal NA Isolation Kit,QIAGEN QIAamp ViralRNA mini Kit
Assay Results	Qualitative	Qualitative	Qualitative
Instrument System	Cepheid GeneXpertInstrument Systems	Cepheid Smartcycler®II	3M Integrated cycler
Assay Controls	Encapsulated (armored)RNA pseudovirus as asample processingcontrol.Available but notprovided are inactivatedvirus controls for Flu A/Band Flu A H1N1 asexternal positive controlsand Coxsackie virus as anexternal negative control.	Inf A RNA Control, InfB RNA Control, RSVA RNA Control, RSVB RNA Control and aninternal	Armored RNA InternalControl, No TemplateControl, and H1N1 PositiveControl provided
Test results	Total 75 minutes for samplepreparation andrRT-PCR	Total 205 minutes(~45 minutes forsample preparation~2.0 hours forrRT-PCR)	Total 115 minutes(~45 minutes for samplepreparation~70 minutes forrRT-PCR)
	Device	Predicates
Item	Cepheid Xpert Flu	Gen-Probe Prodesse,Inc. ProFLU+\	Focus SimplexaInfluenza A H1N1
Laboratory Users	CLIA Moderate to HighComplexity	CLIA High Complexity	CLIA High Complexity

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Non-Clinical Studies:

Analytical Sensitivity

Analytical Reactivity (Inclusivity)

The analytical reactivity of the Xpert Flu Assay was evaluated against thirty-nine (39) strains of influenza A (H1N1, H3N2, H5N2, H5N1, and H7N3 subtypes), influenza A 2009 H1N1 and influenza B. Of these, influenza A subtype H1N1 (12), influenza A subtype H3N2 (7), influenza A subtype 2009 H1N1 (6), influenza A subtype H5N1 (1), influenza A subtype H5N2 (1), influenza A subtype H7N3 (1) and influenza B (11) were included. Three replicates of each viral strain were tested at 5 - 500 TCID50mL unless noted otherwise. Results are shown in Table 5.2.

Viral Strain	Concentration(TCID50/mL)	InfluenzaA	Influenza A2009 H1N1	InfluenzaB
Influenza A/Denver/1/57 (H1N1)	500	+	-	-
Influenza A/NewYork/55/2004 (H1N1)	500	+	-	-
Influenza A/Mal/302/54 (H1N1)	50	+	-	-
Influenza A/New Jersey/8/76 (H1N1)	500	+	-	-
Influenza A/NWS/33 (H1N1)	5	+	-	-
Influenza A/PR/8/34 (H1N1)a	500	+	-	-
Influenza A/Taiwan/42/06 (H1N1)a	500	+	-	-
Influenza A/WS/33 (H1N1)a	5	+	-	-
Influenza A/Swine/1976/31 (SwineH1N1)	500 PFU/mLa	+	-	-
Influenza A/Swine/Iowa/15/30 (SwineH1N1)	500 PFU/mLa	+	-	-
Influenza A/Brisbane/59/07 (H1N1)a	5	+	-	-
Influenza A/NewCalendonia/20/1999(H1N1)a	50	+	-	-
Influenza A/Victoria/3/75 (H3N2)	500	+	.
Viral Strain	Concentration(TCID50/mL)	InfluenzaA	Influenza A2009 H1N1	InfluenzaB
Influenza A/Aichi2/68 (H3N2)	500	+
Influenza A/Hong Kong/8/68 (H3N2)	50	+	-	-
Influenza A/Hawaii/15/2001 (H3N2)	500	+	-	-
Influenza A/Port Chalmers/1/73 (H3N2)	500	+	-	-
Influenza A/Brisbane/10/07 (H3N2)	10	+	-	-
Influenza A/Wisconsin/67/05 (H3N2)	10	+	-	-
Influenza A/SwineNY/01/2009(2009 H1N1)	10	+	+	-
Influenza A/SwineNY/02/2009(2009 H1N1)	100	+	+	-
Influenza A/SwineNY/03/2009(2009 H1N1)	10	+	+	-
Influenza A/California/4/2009(2009 H1N1)	5	+	+	-
Influenza A/Canada/6294(2009 H1N1)	500	+	+	-
Influenza A/WI/929-S1(2009 H1N1)	100	+	+	-
Influenza A/Mallard/WI/34/75 (H5N2)	3 pg/μLb	+	-	-
Influenza A/Anhui/02/2005/PR8-IBCDC-RG5 (H5N1)	0.122 pg/µLb	+	-	-
Influenza A/chicken/NJ/15086-3/94(H7N3)	5 pg/µLb	+	-	-
Influenza B/Allen/45	500	-	-	+
Influenza B/Florida/02/06	10	-	-	+
Influenza B/Florida/04/06	500	-	-	+
Influenza B/Florida/07/04	50	-	-	+
Influenza B/GL/1739/54	500	-	-	+
Influenza B/Hong Kong/5/72	500	-	-	+
Influenza B/Lee/40	500	-	-	+
Influenza B/Malaysia/2506/04	500	-	-	+
Influenza B/Maryland/1/59	500	-	-	+
Viral Strain	Concentration(TCID50/mL)	InfluenzaA	Influenza A2009 H1N1	InfluenzaB
Influenza B/Panama/45/90	500	-	-	+
Influenza B/Taiwan/2/62	50 CEID50/mLc	-	-	+

Table 5.2: Analytical Reactivity (Inclusivity) of Xpert Flu Assay

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Xpert Flu Assay 510(k) Summary

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ªConcentration expressed as PFU/mL

Concentration expressed in picograms/uL Concentration expressed as CEIDsofmL

Analytical Sensitivity

Limit of Detection

Studies were performed to determine the analytical limit of detection (LoD) of two seasonal influenza A (H1N1), two seasonal influenza A (H3N2), five influenza A 2009 HINI and two influenza B strains diluted into a surrogate nasopharyngeal matrix, containing human blood, mucin and sodium chloride. The LoD is defined as the lowest concentration (tissue culture infective dose [TCID]50/mL) 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. Each strain was tested in replicates of 20 per concentration of virus.

The LoD was determined empirically as the first concentration that had 19/20 or 20/20 positive results. The LoD values for each strain tested are summarized in Tables 5.3 -ર .6.

Strain ID - Influenza Asubtype H1N1	Confirmed LoD(TCID50/mL)(at least 19/20 positive)
Influenza A/H1/Brisbane/59/07	5 (20/20)
Influenza A/H1/NewCaledonia/20/1999	25 (20/20)

Table 5.3: Confirmed LoD (TCID50/mL) – Seasonal Influenza A H1N1

Table 5.4: Confirmed LoD (TCID50/mL) - Seasonal Influenza A H3N2

Strain ID - Influenza Asubtype H3N2	Confirmed LOD(TCID50/mL) (at least 19/20 positive)
Influenza A/H3/Brisbane/10/07	2.5 (19/20)
InfluenzaA/H3/Wisconsin/67/05	10 (20/20)

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Strain ID -- Influenza Asubtype 2009 H1N1	Confirmed LOD(TCID50/mL) (at least 19/20 positive)
Influenza A/SwineNY/01/2009	1 (19/20)
Influenza A/SwineNY/02/2009	5 (19/20)
Influenza A/SwineNY/03/2009	3.5 (20/20)
Influenza A/Canada/6294	100 (20/20)
Influenza A/WI/629-S1/2009	20 (20/20)

Table 5.5: Confirmed LoD (TCID50/mL) - Influenza A 2009 H1N1
--------------------------------------------------------------	--	--	--	--

Table 5.6: Confirmed LoD (TCID50/mL) - Influenza B

Strain ID - Influenza B	Confirmed LOD(TCID50/mL) (at least 19/20 positive)
Influenza B/Florida/02/06	2 (19/19)
Influenza B/Florida/07/04	75 (20/20)

Analytical Specificity (Exclusivity)

The analytical specificity of the Xpert Flu Assay was evaluated by testing a panel of 40 cultures consisting of 18 viral, 21 bacterial, and one yeast representing common respiratory pathogens or those potentially encountered in the nasopharynx. Three replicates of each bacterial and yeast strains were tested at concentrations ≥10° CFU/mL. Three replicates of each virus were tested at concentrations ≥10 TCID50/mL. Purified nucleic acids (genome copies/mL) were tested for one virus strain (Cytomegalovirus) and two bacterial strains (Bordetella pertussis and Haemophilus influenzae). Positive and negative controls were included in the study. The analytical specificity was 100%. Results are shown in Table 5.7.

Strain	Concentration(per Cartridge)	InfluenzaA	Influenza A2009 H1N1	InfluenzaB
Positive Control 1 - InfluenzaA/influenza B	N/A	+	-	+
Positive Control 2 – Influenza A2009 H1N1	N/A	+	+	-
Negative Control	N/A	-	-	-
Adenovirus Type 7A	1x106 TCID50/mL	-	-	-
Adenovirus Type 1	1x106 TCID50/mL	-	-	-
Human Coronavirus 229E	1x106 TCID50/mL	-	-	-
Human Coronavirus OC43	1x104 TCID50/mL	-	-	-
Cytomegalovirusb	1x105 Copies /mL	-	-	-
Enterovirus Type 71	1x106 TCID50/mL	-	-	-
Epstein-Barr Virus	1x105 TCID50/mL	-	-	-
Strain	Concentration(per Cartridge)	InfluenzaA	Influenza A2009 H1N1	InfluenzaB
Parainfluenzavirus Type 1	1x105 TCID50/mL	-	-	-
Parainfluenzavirus Type 2	1x106 TCID50/mL	-	-	-
Parainfluenzavirus Type 3	1x106 TCID50/mL	-	-	-
Measles Virus	1x106 TCID50/mL	-	-	-
Human Metapneumovirus	1x106 TCID50/mL	-	-	-
Mumps Virus	1x106 TCID50/mL	-	-	-
Respiratory Syncytial Virus A	1x106 TCID50/mL	-	-	-
Respiratory Syncytial Virus B	1x106 TCID50/mL	-	-	-
Human HSV Type 1	1x106 TCID50/mL	-	-	-
Human Rhinovirus Type 4	1x106 TCID50/mL	-	-	-
Echovirus 11	1x106 TCID50/mL	-	-	-
Bordetella pertussis b	1x106 Copies/mL	-	-	-
Chlamydia pneumoniae	1x106 CFU/mL	-	-	-
Corynebacterium xerosis	1x106 CFU/mL	-	-	-
Escherichia coli	1x106 CFU/mL	-	-	-
Proteus vulgaris	1x106 CFU/mL	-	-	-
Proteus mirabilis	1x106 CFU/mL	-	-	-
Klebsiella pneumoniae	1x106 CFU/mL	-	-	-
Haemophilus influenzae b	1x106 Copies/mL	-	-	-
Lactobacillus crispatus	1x106 CFU/mL	-	-	-
Legionella pneumophila	1x106 CFU/mL	-	-	-
Moraxella catarrhalis	1x106 CFU/mL	-	-	-
Mycobacterium tuberculosis(BCG strain)	1x106 CFU/mL	-	-	-
Mycoplasma pneumoniae	1x106 CFU/mL	-	-	-
Neisseria meningitides	1x106 CFU/mL	-	-	-
Neisseria Cinneria	1x106 CFU/mL	-	-	-
Pseudomonas aeruginosa	1x106 CFU/mL	-	-	-
Staphylococcus aureus	1x106 CFU/mL	-	-	-
Staphylococcus epidermidis	1x106 CFU/mL	-	-	-
Streptococcus pneumoniae	1x106 CFU/mL	-	-	-
Streptococcus pyogenes	1x106 CFU/mL	-	-	-
Streptococcus salivarius	1x106 CFU/mL	-	-	-
Candida albicans	1x106 CFU/mL	-	-	-

Table 5.7: Analytical Specificity of Xpert Flu Assayª

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a Cross-reactivity with other swine-origin strains was not evaluated. bNucleic acid was tested for Cytomegalovirus, Bordetella pertussis, and Haemophilus influenzae.

Interfering Substances

In a non-clinical study, potentially interfering substances that may be present in the nasopharynx were evaluated directly relative to the performance of the Xpert Flu Assay. Potentially interfering exogenous substances in the nasopharynx may include, but are not limited to: blood, nasal secretions or mucus, and nasal and throat medications used to relieve congestion, nasal dryness, irritation, or asthma and allergy symptoms. These substances are listed in Table 5.8 with active ingredients and concentrations tested shown. Highly viscous samples, resulting from the addition of 1.5% (w/v) and 2.5% (w/v) mucin yielded false negative test results from the Xpert Flu Assay. Inhibition of the Xpert Flu Assay was also observed from the addition of 1% (w/v) mucin, resulting in delayed detection of influenza A, influenza A subtype 2009 H1N1 and influenza B.

Substance	Description/Active Ingredient	Concentration Tested
Blood (human)	N/A	2% (v/v)
Mucin	Purified mucin protein (Bovine or porcine submaxillary gland)	2.5%, 1.5%, 1% and 0.5% (w/v)
Neo-Synephrine® Nasal Drops	Phenylephrine HCl	15% (v/v)
Anefrin Nasal Spray	Oxymetazoline Hydrochloride	15% (v/v)
Zicam® Nasal Gel	Luffa opperculata, Galphimia glauca, Histaminum hydrochloricum Sulfur	5% (v/v)
Saline Nasal Spray	Sodium Chloride with preservatives	15% (v/v)
Antibiotic, nasal ointment	Mupirocin	10 mg/mL
Antibacterial, systemic	Tobramycin	4.0 µg/mL
Throat lozenges, oral anesthetic and analgesic	Menthol	1.7 mg/mL menthol

Table 5.8: Potentially Interfering Substances in Xpert Flu Assay.

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Carry-Over Contamination Study

A study was conducted to demonstrate that single-use, self-contained GeneXpert cartridges prevent carry-over contamination in negative samples run following very high 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 influenza A subtype 2009 H1N1 sample (approximately 10° TCID50/test) or influenza B sample (approximately 10° TCID50/test). This testing scheme was repeated 20 times on four GeneXpert modules for a total of 88 runs resulting in 40 positive and 48 negative specimens. All 40 positive samples were correctly reported as influenza A 2009 H1N1 positive or influenza B positive. All 48 negative samples were correctly reported as Flu A negative, 2009 H1N1 not detected and Flu B negative.

Linearity

A study was conducted to define the reportable range of the Xpert Flu Assay and demonstrate a linear relationship between target input and assay output. Linearity was evaluated using two seasonal influenza A H1N1, two seasonal influenza A H3N2, two influenza A 2009 H1N1, and two influenza B strains diluted over four to five logs and processed using the Xpert Flu Assay. Replicates of 4 were tested.

Under the conditions of the study, the Xpert Flu Assay responds linearly over six logs for seasonal influenza A H1N1, seasonal influenza A H3N2 and influenza A 2009 H1N1; and over 5 logs for influenza B strains tested.

Reproducibility

A panel of 10 specimens with varying concentrations of influenza A, influenza B, and influenza A subtype 2009 H1N1 were tested in duplicate on 10 different days at each of three sites (10 specimens x 2 times/ day x 10 days x 3 sites). One lot of Xpert Flu Assay was used at each of the 3 testing sites. Xpert Flu Assays were performed according to the Xpert Flu Assay procedure. Results are summarized in Table 5.9.

Sample ID	Site 1	Site 2	Site 3	% Total Agreementby Sample
Negative	100%(20/20)	100%(20/20)	100%(20/20)	100%(60/60)
Flu Amoderate positive	100%(20/20)	100%(19/19)a	100%(20/20)	100%(59/59)
Flu Alow positive	100%(20/20)	100%(20/20)	100%(20/20)	100%(60/60)
Flu Ahigh negative	100%(20/20)	95.0%(19/20)	90.0%(18/20)	95.0%(57/60)
2009 H1N1moderate positive	100%(20/20)	100%(20/20)	100%(20/20)	100%(60/60)
2009 H1N1low positive	100%(20/20)	100%(19/19)b	100%(20/20)	100%(59/59)

Table 5.9: Summary of Reproducibility Results

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Sample ID	Site 1	Site 2	Site 3	% Total Agreementby Sample
2009 H1N1high negative	94.7%(18/19)a	100%(20/20)	89.5%(17/19)a	94.8%(55/58)c
Flu Bmoderate positive	100%(20/20)	100%(20/20)	100%(20/20)	100%(60/60)
Flu Blow positive	100%(20/20)	100%(20/20)	100%(20/20)	100%(60/60)
Flu Bhigh negative	90.0%(18/20)	95.0%(19/20)	55.0%(11/20)	80.0%(48/60)
% Total Agreement	98.5%(196/199)	99.0%(196/198)	93.5%(186/199)	97.0%(578/596)

*n=19 because repeat yielded indeterminate result.

be = 19 because one sample was indeterminate and not retested.

59/55 samples negative for 2009 HINI resulted in a valid Flu A positive call, as the Flu A signal was detected. A valid 2009 HINI positive call requires detection of both the Flu A and 2009 HINI signals.

Instrument System Reproducibility

An in-house reproducibility study was conducted to compare the performance of the GeneXpert Dx and the Infinity instrument systems. A panel of 10 specimens with varying concentrations of influenza A, influenza B, and influenza A subtype 2009 H1N1 were tested in duplicate on 12 different days by two operators. Each operator conducted four runs of each panel specimen per day on each of the two instrument systems (11 specimens x 2 times/ day x 12 days x 2 operators x 2 instrument systems). One lot of Xpert Flu Assay was used for the study. Xpert Flu Assays were performed according to the Xpert Flu Assay procedure. Results are summarized in Table 5.10.

Sample ID	GeneXpert Dx	Infinity	% Total Agreementby Sample
Negative	100.0%(96/96)	100.0%(96/96)	100.0%(192/192)
Flu Amoderate positive	100.0%(96/96)	100.0%(96/96)	100.0%(192/192)
Flu Alow positive	100.0%(96/96)	100.0%(96/96)	100.0%(192/192)
Flu Ahigh negative	89.6%(86/96)	86.5%(83/96)	88.0%(169/192)
2009 H1N1moderate positive	100.0%(96/96)	100.0%(96/96)	100.0%(192/192)
2009 H1N1low positive	100.0%(96/96)	100.0%(96/96)	100.0%(192/192)
2009 H1N1high negative	84.4%(81/96)	92.6%(88/95)a	88.5%(169/191)
Flu Bmoderate positive	100.0%(96/96)	100.0%(96/96)	100.0%(192/192)

Table 5.10: Summary of Instrument System Reproducibility Results

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Sample ID	GeneXpert Dx	Infinity	% Total Agreementby Sample
Flu Blow positive	100.0%(96/96)	100.0%(96/96)	100.0%(192/192)
Flu Bhigh negative	87.5%(84/96)	82.3%(79/96)	84.9%(163/192)
% Total Agreement	96.1%(923/960)	96.1%(922/959)	96.1%(1845/1919)

ªn=95 because repeat yielded indeterminate result.

Clinical Performance Characteristics

Clinical Performance Study

Performance characteristics of the Xpert Flu Assay on prospective and archived specimens were evaluated at six institutions in the U.S. and Australia. Due to the low prevalence of influenza viruses and the difficulty in obtaining fresh influenza-positive specimens, the specimen population for this study was supplemented with frozen archived specimens.

Subjects included individuals whose routine care called for collection of NA/W or NP swab specimens for influenza testing. For eligible subjects, aliquots of leftover sample were obtained for testing with the Xpert Flu Assay and reference testing, and patient management continued at the site per the standard practice.

The Xpert Flu Assay performance was compared to viral culture followed by direct fluorescent assay (DFA). Sequencing was performed for all influenza A positive specimens. For archived specimens, where viral culture was not performed prior to freezing, a FDA cleared molecular assay was performed as the comparator assay. Samples included nasal NA/W and NP swab specimens collected for routine testing from patients suspected of influenza infection.

Overall Results

Prospective Specimens

A total of 342 prospective NA/W specimens were tested for influenza A, influenza A subtype 2009 H1N1 and influenza B by the Xpert Flu Assay and viral culture plus DFA. A total of 297 prospectively collected NP swab specimens were tested for influenza A, influenza A subtype 2009 H1N1 and influenza B by the Xpert Flu Assay and viral culture plus DFA. All influenza A positive specimens, identified by viral culture/DFA, were sequenced to differentiate influenza A subtype 2009 H1N1 from other influenza A subtypes

On fresh, prospective NA/W specimens, the Xpert Flu Assay demonstrated a sensitivity and specificity for detection of influenza A of 85.7% and 99.1%, respectively, relative to viral culture plus DFA, with sequence confirmation of all influenza A positive viral isolates, or specimens in transport medium if isolates were not available (Table 5.11).

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The Xpert Flu Assay sensitivity and specificity for influenza A subtype 2009 H1N1 with NA/W specimens were 100% and 98.8%, respectively (Table 5.12). The Xpert Flu Assay sensitivity and specificity for influenza B with NA/W specimens were 100% and 99.4%, respectively (Table 5.13).

	Culture/DFA
pert Flu Assa		Pos	Neg	Total
	Pos	6	3 สิ	ರ
	Neg	l b	332	333
	Total	7	335	342
	85.7% (95% CI: 42.1-99.6)Sensitivity:99.1% (95% CI: 97.4-99.8)Specificity:

Table 5.11: Xpert Flu Assay Performance on Prospective NA/W Specimens: Influenza A

4Testing results by sequencing: 3 of 3 were H1N1.

bTesting results by sequencing: Flu A

Table 5.12: Xpert Flu Assay Performance on Prospective NA/W Specimens: Influenza A, 2009 H1N1

	Culture/DFA & Sequencing
	Pos	Neg	Total
Xpert Flu Assay	Pos	4	4a	8
	Neg	0	334	334
	Total	4	338	342
Sensitivity: 100% (95% CI: 39.8-100)Specificity: 98.8% (95% CI: 97.0-99.7)

Testing results by sequencing: 3 of 4 were HINI; 1 of 4 was Flu A.

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	Culture/DFA
Xpert Flu Assay	Pos	Neg	Total
Pos	7	2a	9
Neg	0	333	333
Total	7	335	342
		Sensitivity: 100% (95% CI: 65.2-100)
		Specificity: 99.4% (95% CI: 98.1-99.9)

Table 5.13: Xpert Flu Assay Performance on Prospective NA/W Specimens: Influenza B

ªTesting results by sequencing: 2 of 2 were Flu B.

On prospectively collected NP swabs, the Xpert Flu Assay demonstrated a sensitivity and specificity for detection of influenza A of 100% and 98.3%, respectively, relative to viral culture plus DFA, with sequence confirmation of all influenza A positive viral isolates, or specimens in transport medium if isolates were not available (Table 5.14). The Xpert Flu Assay sensitivity and specificity for influenza A subtype 2009 HIN1 with NP swabs were 100% and 99.0%, respectively (Table 5.15). The Xpert Flu Assay sensitivity and specificity for influenza B with NP swabs were 87.5% and 99.7%, respectively (Table 5.16).

Table 5.14: Xpert Flu Assay Performance on Prospective NP Swab Specimens: Influenza A

	Culture/DFA
Xpert Flu Assay		Pos	Neg	Total
	Pos	7	5a	12
	Neg	0	285	285
Total		7	290	297
	Sensitivity: 100% (95% CI: 59.0-100)Specificity: 98.3% (95% CI: 96.0-99.4)

4Testing results by sequencing: 3 of 5 were H1N1; 2 of 5 were Flu A.

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	Culture/DFA & Sequencing
Xpert Flu Assay	Pos	Neg	Total
Pos	5	3a	8
Neg	0	289	289
Total	5	292	297
	Sensitivity:Specificity:		100% (95% CI: 47.8-100)99.0% (95% CI: 97.0-99.8)

Table 5.15: Xpert Flu Assay Performance on Prospective NP Swab Specimens: Influenza A, 2009 H1N1

ªTesting results by sequencing: 2 of 3 were H1N1; 1 of 3 was Flu A.

Table 5.16: Xpert Flu Assay Performance on Prospective NP Swab Specimens: Influenza B

	Culture/DFA
Xpert Flu Assay		Pos	Neg	Total
	Pos	7	1a	8
	Neg	1b	288	289
	Total	8	289	297
	Sensitivity: 87.5% (95% CI: 47.3-99.7)Specificity: 99.7% (95% CI: 98.1-100)

a Testing results by sequencing: Flu B. bTesting results by sequencing: Flu A.

Archived Specimens

A total of 425 archived NA/W specimens were tested for influenza A, influenza A subtype 2009 H1N1 and influenza B by the Xpert Flu Assay and a FDA cleared molecular comparator device. A total of 150 archived NP swab specimens were tested for influenza A. influenza A subtype 2009 H1N1 and influenza B by the Xpert Flu Assay and viral culture plus DFA: 177 archived NP swab specimens did not have viral culture results available and were tested by the FDA cleared molecular comparator device. All influenza A positive specimens indentified by viral culture/DFA or cleared molecular comparator device were sequenced to differentiate influenza A subtype 2009 HINI from other influenza A subtypes.

On archived NA/W specimens, the Xpert Flu Assay demonstrated a positive and negative agreement for detection of influenza A of 99.4% and 100%, respectively, relative to viral culture plus DFA, with sequence confirmation of all influenza A positive viral isolates, or

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specimens in transport medium if isolates were not available (Table 5.17). The Xpert Flu Assay positive and negative agreement for influenza A subtype 2009 H1N1 with NA/W specimens were 98.4% and 99.7% (Table 5.18). The Xpert Flu Assay positive and negative agreement for influenza B with NA/W specimens were 100% and 100%, respectively (Table 5.19)

	FDA Cleared Molecular Comparator
Xpert Flu Assay		Pos	Neg	Total
	Pos	159	0	159
	Neg	1*	265	266
	Total	160	265	425
	Positive Agreement:Negative Agreement:		99.4% (95% CI: 96.6-100)100% (95% CI: 98.6-100)

Table 5.17: Xpert Flu Assay Performance on Archived NA/W Specimens: Influenza A

1Testing by sequencing: no sequence match for Flu A, HIN1 or Flu B

Table 5.18: Xpert Flu Assay Performance on Archived NA/W Specimens: Influenza A, 2009 H1N1

	FDA Cleared Molecular Comparator & Sequencing
Xpert Flu Assay	Pos	Neg	Total
Pos	124	1a	125
Neg	2b	295	297
Total	126	296	422c
	Positive Agreement:Negative Agreement:		98.4% (95% CI: 94.4-99.8)99.7% (95% CI: 98.1-100)

aTesting results by sequencing: Flu A, not HINI.

6Testing results by sequencing: 2 of 2 HIN1.

63 samples excluded due to PHRED score <20.

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	FDA Cleared Molecular Comparator
	Pos	Neg	Total
Xpert Flu Assay	Pos	40	0	40
	Neg	0	385	385
	Total	40	385	425
	Positive Agreement:Negative Agreement:		100% (95% CI: 91.2-100)100% (95% CI: 99.0-100)

Table 5.19: Xpert Flu Assay Performance on Archived NA/W Specimens: Influenza B

On archived NP swabs, the Xpert Flu Assay demonstrated a positive and negative agreement for detection of influenza A of 97.5% and 100%, respectively, relative to viral culture plus DFA, with sequence confirmation of all influenza A positive viral isolates, or specimens in transport medium if isolates were not available (Table 5.20). The Xpert Flu Assay positive and negative agreement for influenza A subtype 2009 H1N1 with NP swabs were 100% and 100%, respectively (Table 5.21). The Xpert Flu Assay positive and negative for influenza B with NP swabs were 93.8% and 99.2%, respectively (Table 5.22).

Table 5.20: Xpert Flu Assay Performance vs. Comparator Method with NP Swab Specimens: Influenza A

	Culture/DFA
Xpert Flu Assay	Pos	Neg	Total
Pos	115	0	115
Neg	3a	32	35
Total	118	32	150
Positive Agreement: 97.5% (95% CI: 92.7-99.5)
Negative Agreement: 100% (95% CI: 89.1-100)

aTesting results by sequencing: 2 of 3 were no sequence match for Flu A, HINI, or Flu B; 1 of 3 was Flu B.

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	Culture/DFA & Sequencing
Xpert Flu Assay		Pos	Neg	Total
	Pos	84	0	84
	Neg	0	65	65
	Total	84	65	149a
		Positive Agreement:		100% (95% CI: 95.7-100)
		Negative Agreement:		100% (95% CI: 94.5-100)

Table 5.21: Xpert Flu Assay Performance vs. Comparator Method with NP Swab Specimens: 2009 H1N1

4One sample excluded due to PHRED score <20.

Table 5.22: Xpert Flu Assay Performance vs. Comparator Method with NP Swab-Specimens: Influenza B

	Culture/DFA
Xpert Flu Assay	Pos	Neg	Total
Pos	30	1a	31
Neg	2b	117	119
Total	32	118	150
	Positive Agreement: 93.8% (95% CI: 79.2-99.2)
	Negative Agreement: 99.2% (95% CI: 95.4-100)

ªTesting results by sequencing: Flu B.

Testing results by sequencing: no sequence match for Flu A, HIN1 or Flu B.

On archived NP swabs, the Xpert Flu Assay demonstrated a positive agreement and negative agreement for detection of influenza A of 98.1% and 99.2%, respectively, relative to the comparator assay, with sequence confirmation of all influenza A positive viral isolates, or specimens in transport medium if isolates were not available (Table 5.23). The Xpert Flu Assay positive and negative agreement for influenza A subtype 2009 H1N1 with NP swabs were 100% and 99.3%, respectively (Table 5.24). The Xpert Flu Assay positive and negative agreements for influenza B with NP swabs were 93.8% and 100%, respectively (Table 5.25).

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Influenza A
Xpert Flu Assay		Pos	Neg	Total
	Pos	51	1a	52
	Neg	1b	120	121
	Total	52	121	173
	Positive Agreement:Negative Agreement:		98.1% (95% CI: 89.7-100)99.2% (95% CI: 95.5-100)

Table 5.23: Xpert Flu Assay Performance on Archived NP Swab Specimens: Influenza A

4No test results by sequencing available.

bTesting results by sequencing: Flu A

Table 5.24: Xpert Flu Assay Performance vs. Comparator Method with NP Swab Specimens: 2009 H1N1

	FDA Cleared Molecular Comparator & Sequencing
Xpert Flu Assay		Pos	Neg	Total
	Pos	29	1a	30
	Neg	0	142	142
	Total	29	143	172b
	Positive Agreement:Negative Agreement:		100% (95% CI: 88.1-100)99.3% (95% CI: 96.2-100)

*No test results available.

Sequence confirmation not available for one sample.

Table 5.25: Xpert Flu Assay Performance vs. Comparator Method with NP Swab Specimens: Influenza B

	FDA Cleared Molecular Comparator
Xpert Flu Assay	Pos	Neg	Total
Pos	15	0	15
Neg	1a	157	158
Total	16	157	173
Positive Agreement: 93.8% (95% CI: 69.8-99.8)Negative Agreement: 100% (95% CI: 97.7-100)

No test results by sequencing available.

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Of the Xpert Flu Assays runs performed with eligible specimens, 97.1% (1351/1391) of these specimens were successful on the first attempt. The remaining 40 gave indeterminate results on the first attempt (26 ERROR, 10 INVALID and 4 NO RESULT). Thirty-six of the 40 specimens vielded valid results after a single retest; four of the specimens were indeterminate on the second attempt. The assay success rate was equivalent for archived [96.8% (727/751)] and fresh [97.5% (624/640)] specimens.

Conclusions

The results of the nonclinical analytical and clinical performance studies summarized above demonstrate that the Xpert Flu Assay is as safe and effective as the reference method, and therefore is substantially equivalent to the predicate devices.

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Image /page/22/Picture/1 description: The image shows the logo for the U.S. Department of Health & Human Services. The logo consists of a circular border with the text "DEPARTMENT OF HEALTH & HUMAN SERVICES - USA" arranged around the circumference. Inside the circle is an abstract symbol resembling a stylized caduceus or a bird in flight, composed of three curved lines.

Food and Drug Administration 10903 New Hampshire Avenue Silver Spring, MD 20993

Cepheid® c/o Kerry J. Flom. Ph.D. Senior Vice President, Clinical Affairs and Regulatory Submissions 904 Caribbean Drive Sunnyvale, California 94089-1189

APR 2 1 201

Re: K103766

Trade/Device Name: Xpert Flu Assay Regulation Number: 21 CFR§ 866.3980 Regulation Name: Respiratory viral panel multiplex nucleic acid assay Regulatory Class: Class II Product Code: OOW,OCC, OOI Dated: March 04, 2011 Received: March 07, 2011

Dear Dr. Flom:

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.

If your device is classified (see above) into class II (Special Controls), it may be subject to such additional controls. Existing major regulations affecting your device can be found in Title 21, Code of Federal Regulations (CFR), Parts 800 to 895. 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); and good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820). This letter

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Page 2 - Kerry J. Flom

will allow you to begin marketing your device as described in your Section 510(k) premarket notification. The FDA finding of substantial equivalence of your device to a legally marketed predicate device results in a classification for your device and thus, permits your device to proceed to the market.

If you desire specific advice for your device on our labeling regulation (21 CFR Parts 801 and 809), please contact the Office of In Vitro Diagnostic Device Evaluation and Safety at (301) 796-5450. 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 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/cdrh/industry/support/index.html.

Sincerely yours,

Sally A. Hojvat, M.Sc., Ph.D. Director Division of Microbiology Devices Office of In Vitro Diagnostic Device Evaluation and Safety Center for Devices and Radiological Health

Enclosure

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4.0 Indications for Use Form

510(k) Number (if known): K103766

Device Name: Xpert® Flu Assay

Indications for Use:

Negative results do not preclude influenza virus infection and should not be used as the sole basis for treatment or other patient management decisions.

If infection with a novel influenza A virus is suspected based on current clinical and enidemiological screening criteria recommended by public health authorities, specimens should be collected with appropriate infection control precautions for novel virulent influenza viruses and sent to state or local health department for testing. Viral culture should not be attempted in these cases unless a BSL 3+ facility is available to receive and culture specimens.

Prescription Use X(Part 21 CFR 801 Subpart D)	AND/OR Over-The-Counter Use(21 CFR 801 Subpart C)
---------------------------------------------------	-------------------------------------------------------

(PLEASE DO NOT WRITE BELOW THIS LINE-CONTINUE ON ANOTHER PAGE OF NEEDED)

Concurrence of CDRH. Office of In Vitro Diagnostic Devices (OIVD)

Jauzatapir

Division Sign-Off

Office of In Vitro Diagnostic Device Evaluation and Safety

510(k) K103766.

Page 1 of 1

Regulation Number and Section

§ 866.3332 Reagents for detection of specific novel influenza A viruses.

(a)
Identification. Reagents for detection of specific novel influenza A viruses are devices that are intended for use in a nucleic acid amplification test to directly detect specific virus RNA in human respiratory specimens or viral cultures. Detection of specific virus RNA aids in the diagnosis of influenza caused by specific novel influenza A viruses in patients with clinical risk of infection with these viruses, and also aids in the presumptive laboratory identification of specific novel influenza A viruses to provide epidemiological information on influenza. These reagents include primers, probes, and specific influenza A virus controls.(b)
Classification. Class II (special controls). The special controls are:(1) FDA's guidance document entitled “Class II Special Controls Guidance Document: Reagents for Detection of Specific Novel Influenza A Viruses.” See § 866.1(e) for information on obtaining this document.
(2) The distribution of these devices is limited to laboratories with experienced personnel who have training in standardized molecular testing procedures and expertise in viral diagnosis, and appropriate biosafety equipment and containment.