Sofia Influenza A+B FIA on Sofia 2

K162438 · Quidel Corporation · PSZ · Apr 14, 2017 · Microbiology

Device Facts

• Record ID: K162438
• Device Name: Sofia Influenza A+B FIA on Sofia 2
• Applicant: Quidel Corporation
• Product Code: PSZ · Microbiology
• Decision Date: Apr 14, 2017
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 866.3328
• Device Class: Class 2

Intended Use

The Sofia Influenza A+B FIA employs immunofluorescence to detect influenza A and influenza B viral nucleoprotein antigens in direct nasal swab, nasopharyngeal swab, and nasopharyngeal aspirate/wash specimens and nasopharyngeal swab and nasopharyngeal aspirate/wash specimens in transport media from symptomatic patients. This qualitative test is intended for use as an aid in the rapid differential diagnosis of acute influenza A and influenza B viral infections. The test is not intended to detect influenza C antigens. A negative test is presumptive and it is recommended these results be confirmed by viral culture or an FDA-cleared influenza A and B molecular assay. Negative results do not preclude influenza virus infections and should not be used as the sole basis for treatment or other patient management decisions. This test is intended for professional and laboratory use. The Sofia Influenza A+B FIA may be used with Sofia or Sofia 2.

Device Story

Sofia 2 is a microprocessor-controlled, desktop-sized immunofluorescence analyzer for detecting influenza A and B viral nucleoproteins. Input: patient samples (nasal/nasopharyngeal swabs or aspirates/washes) processed in reagent tubes to disrupt virus particles, then applied to test cassettes. Operation: cassettes inserted into Sofia 2 for automated scanning of test strips via UV light source and fluorescent tag detection. Modes: 'Walk Away' (automated timing) or 'Read Now' (manual timing). Output: qualitative results (Positive/Invalid) displayed on touchscreen or printed. Used in professional/laboratory settings by clinicians/technicians. Device aids rapid differential diagnosis; negative results require confirmation by culture or molecular assay. Benefits include faster clinical decision-making and point-of-care testing capability.

Clinical Evidence

Bench testing only. Studies compared Sofia 2 to the predicate Sofia system, including Limit of Detection (LoD), precision, reproducibility (intra/inter-operator and intra/inter-laboratory), and method comparison using clinical sample panels. Results confirmed equivalent qualitative performance between the two systems. Early read capability in 'Walk Away' mode allows positive detection as early as 3 minutes depending on viral load.

Technological Characteristics

Lateral flow immunoassay; UV LED excitation; CMOS camera (Sofia 2) or motorized optics (Sofia); qualitative output; 100-240 VAC or battery power; integrated barcode scanner; touchscreen interface; embedded assay-specific algorithms; professional/laboratory use.

Indications for Use

Indicated for symptomatic patients requiring rapid differential diagnosis of acute influenza A and B viral infections. Specimens include direct nasal swabs, nasopharyngeal swabs, and nasopharyngeal aspirate/wash, including those in transport media. Not for influenza C detection. Professional and laboratory use only.

Regulatory Classification

Identification

An influenza virus antigen detection test system is a device intended for the qualitative detection of influenza viral antigens directly from clinical specimens in patients with signs and symptoms of respiratory infection. The test aids in the diagnosis of influenza infection and provides epidemiological information on influenza. Due to the propensity of the virus to mutate, new strains emerge over time which may potentially affect the performance of these devices. Because influenza is highly contagious and may lead to an acute respiratory tract infection causing severe illness and even death, the accuracy of these devices has serious public health implications.

Special Controls

*Classification.* Class II (special controls). The special controls for this device are:(1) The device's sensitivity and specificity performance characteristics or positive percent agreement and negative percent agreement, for each specimen type claimed in the intended use of the device, must meet one of the following two minimum clinical performance criteria: (i) For devices evaluated as compared to an FDA-cleared nucleic acid based-test or other currently appropriate and FDA accepted comparator method other than correctly performed viral culture method: (A) The positive percent agreement estimate for the device when testing for influenza A and influenza B must be at the point estimate of at least 80 percent with a lower bound of the 95 percent confidence interval that is greater than or equal to 70 percent. (B) The negative percent agreement estimate for the device when testing for influenza A and influenza B must be at the point estimate of at least 95 percent with a lower bound of the 95 percent confidence interval that is greater than or equal to 90 percent. (ii) For devices evaluated as compared to correctly performed viral culture method as the comparator method: (A) The sensitivity estimate for the device when testing for influenza A must be at the point estimate of at least 90 percent with a lower bound of the 95 percent confidence interval that is greater than or equal to 80 percent. The sensitivity estimate for the device when testing for influenza B must be at the point estimate of at least 80 percent with a lower bound of the 95 percent confidence interval that is greater than or equal to 70 percent. (B) The specificity estimate for the device when testing for influenza A and influenza B must be at the point estimate of at least 95 percent with a lower bound of the 95 percent confidence interval that is greater than or equal to 90 percent. (2) When performing testing to demonstrate the device meets the requirements in paragraph (b)(1) of this section, a currently appropriate and FDA accepted comparator method must be used to establish assay performance in clinical studies. (3) Annual analytical reactivity testing of the device must be performed with contemporary influenza strains. This annual analytical reactivity testing must meet the following criteria: (i) The appropriate strains to be tested will be identified by FDA in consultation with the Centers for Disease Control and Prevention (CDC) and sourced from CDC or an FDA-designated source. If the annual strains are not available from CDC, FDA will identify an alternative source for obtaining the requisite strains. (ii) The testing must be conducted according to a standardized protocol considered and determined by FDA to be acceptable and appropriate. (iii) By July 31 of each calendar year, the results of the last 3 years of annual analytical reactivity testing must be included as part of the device's labeling. If a device has not been on the market long enough for 3 years of annual analytical reactivity testing to have been conducted since the device received marketing authorization from FDA, then the results of every annual analytical reactivity testing since the device received marketing authorization from FDA must be included. The results must be presented as part of the device's labeling in a tabular format, which includes the detailed information for each virus tested as described in the certificate of authentication, either by: (A) Placing the results directly in the device's § 809.10(b) of this chapter compliant labeling that physically accompanies the device in a separate section of the labeling where the analytical reactivity testing data can be found; or (B) In the device's label or in other labeling that physically accompanies the device, prominently providing a hyperlink to the manufacturer's public Web site where the analytical reactivity testing data can be found. The manufacturer's home page, as well as the primary part of the manufacturer's Web site that discusses the device, must provide a prominently placed hyperlink to the Web page containing this information and must allow unrestricted viewing access. (4) If one of the actions listed at section 564(b)(1)(A)-(D) of the Federal Food, Drug, and Cosmetic Act occurs with respect to an influenza viral strain, or if the Secretary of Health and Human Services (HHS) determines, under section 319(a) of the Public Health Service Act, that a disease or disorder presents a public health emergency, or that a public health emergency otherwise exists, with respect to an influenza viral strain: (i) Within 30 days from the date that FDA notifies manufacturers that characterized viral samples are available for test evaluation, the manufacturer must have testing performed on the device with those viral samples in accordance with a standardized protocol considered and determined by FDA to be acceptable and appropriate. The procedure and location of testing may depend on the nature of the emerging virus. (ii) Within 60 days from the date that FDA notifies manufacturers that characterized viral samples are available for test evaluation and continuing until 3 years from that date, the results of the influenza emergency analytical reactivity testing, including the detailed information for the virus tested as described in the certificate of authentication, must be included as part of the device's labeling in a tabular format, either by: (A) Placing the results directly in the device's § 809.10(b) of this chapter compliant labeling that physically accompanies the device in a separate section of the labeling where analytical reactivity testing data can be found, but separate from the annual analytical reactivity testing results; or (B) In a section of the device's label or in other labeling that physically accompanies the device, prominently providing a hyperlink to the manufacturer's public Web site where the analytical reactivity testing data can be found. The manufacturer's home page, as well as the primary part of the manufacturer's Web site that discusses the device, must provide a prominently placed hyperlink to the Web page containing this information and must allow unrestricted viewing access.

Predicate Devices

• Sofia Influenza A+B FIA on Sofia (K153012, K131606, and K112177)

Submission Summary (Full Text)

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# 510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY

A. 510(k) Number:
K162438

B. Purpose for Submission:
To demonstrate equivalent performance of the Sofia® Influenza A+B FIA on the Sofia and Sofia 2 analyzers using elements of an assay migration study approach.

C. Measurand:
Influenza A and B nucleoprotein antigens

D. Type of Test:
Qualitative immunofluorescence assay

E. Applicant:
Quidel Corporation

F. Proprietary and Established Names:
Sofia® Influenza A+B FIA on Sofia 2

G. Regulatory Information:

1. Regulation Section:
21 CFR 866.3328, Influenza virus antigen detection test system

2. Classification:
Class II

3. Product Code(s):
PSZ- Devices detecting influenza A, B, and C virus antigens

4. Panel:
Microbiology (83)

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H. Intended Use:

1. Intended Use(s):

The Sofia Influenza A+B FIA employs immunofluorescence to detect influenza A and influenza B viral nucleoprotein antigens in direct nasal swab, nasopharyngeal swab, and nasopharyngeal aspirate/wash specimens and nasopharyngeal swab and nasopharyngeal aspirate/wash specimens in transport media from symptomatic patients. This qualitative test is intended for use as an aid in the rapid differential diagnosis of acute influenza A and influenza B viral infections. The test is not intended to detect influenza C antigens. A negative test is presumptive and it is recommended these results be confirmed by viral culture or an FDA-cleared influenza A and B molecular assay. Negative results do not preclude influenza virus infections and should not be used as the sole basis for treatment or other patient management decisions. This test is intended for professional and laboratory use.

The Sofia Influenza A+B FIA may be used with Sofia or Sofia 2.

Performance characteristics for influenza A and B were established during February through March 2011 when influenza viruses A/California/7/2009 (2009 H1N1), A/Perth/16/2009 (H3N2), and B/Brisbane/60/2008 (Victoria-Like) were the predominant influenza viruses in circulation according to the Morbidity and Mortality Weekly Report from the CDC entitled "Update: Influenza Activity--United States, 2010-2011 Season, and Composition of the 2011-2012 Influenza Vaccine." Performance characteristics may vary against other emerging influenza viruses.

If infection with a novel influenza virus is suspected based on current clinical and epidemiological screening criteria recommended by public health authorities, samples 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 samples.

2. Indication(s) for Use:

Same as intended use

3. Special Conditions for Use Statement(s):

For prescription use only

4. Special Instrument Requirements:

To be used only with Sofia or Sofia 2 analyzers

I. Device Description:

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1. Overview

The Sofia Influenza A+B FIA is a rapid lateral flow immunoassay for the qualitative detection of influenza A and influenza B nucleoprotein in direct nasal swab (NS), nasopharyngeal swab (NP), and nasopharyngeal aspirate/wash (NA/W) specimens and NP and NA/W specimens in transport media collected from patients with signs and symptoms of respiratory infection. The Sofia Influenza A+B FIA components have not been modified; detailed description of the lateral flow device is available in submissions K153012 and K112177, describing the Sofia Influenza A+B FIA use with the original Sofia analyzer.

The purpose of this submission is to obtain 510(k) clearance for the Sofia Influenza A+B FIA for use with the newly developed Sofia 2 analyzer. The Sofia and Sofia 2 analyzers are similar in function and design. Both systems utilize the same fail-safes and failure alert mechanisms, the same calibration and assay-specific cartridges, and the same ultraviolet light-emitting diodes (UV LEDs) to excite the fluorophore. The primary difference between the original Sofia and Sofia 2 analyzer is the design of the optical detection system. Sofia uses a motorized optics unit to collect fluorescent signal data as it performs a series of scans across the longitudinal axis of the Sofia Influenza A+B FIA test strip, whereas Sofia 2 captures a still image of the entire test strip window using a complimentary color-oxide semiconductor (CMOS) camera. To emulate Sofia, the Sofia 2 analyzer converts pixels captured by the CMOS camera to fluorescent signal data, which is analyzed in an equivalent manner to Sofia to yield qualitative test results.

2. Quality Control

See decision summary for K112177.

3. Results Interpretation

There are five possible test results for the Sofia Influenza A+B FIA: influenza A and/or influenza B positive, influenza A and influenza B negative, or invalid. Influenza A and B dual positive result should be re-tested and repeated; dual positive result should be confirmed by virus culture or an FDA-cleared influenza A and B molecular assay. If an invalid test result is reported, the Sofia Influenza FIA should be repeated with a new patient sample and a new test cassette.

Note: The Sofia and Sofia 2 analyzers may be set to one of two operating modes: Walk Away or Read Now. Time to results for the Sofia and Sofia 2 analyzer are described below.

- In Walk Away Mode, the user inserts the test cassette into the analyzer immediately following addition of the specimen to the Sofia Influenza A+B FIA sample port. The Sofia analyzer automatically times the test development and provides positive or negative test results after 15 minutes. The Sofia 2 analyzer scans the test cassette periodically during the test development time and displays a positive test result

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between 3 and 15 minutes. If the test is negative, the result will be displayed after 15 minutes.

- In the Read Now Mode, the user incubates the test cassette on the benchtop for 15 minutes before inserting the cassette into the Sofia or Sofia 2 analyzer. Positive and negative test results are displayed within 1 minute.

## J. Substantial Equivalence Information:

1. Predicate Device Name(s):

Sofia Influenza A+B FIA on Sofia

2. Predicate 510(k) Number:

K153012

3. Comparison with Predicate:

Table 1: Comparison with the Predicate Device

| Similarities and Differences | | |
| --- | --- | --- |
| | Predicate Device | Proposed Device |
| Item | Sofia Influenza A+B FIA on Sofia (K153012) | Sofia Influenza A+B FIA on Sofia 2 (K162438) |
| Regulation | 866.3328 | 866.3328 |
| Product code | PSZ | PSZ |
| Device class | II | II |
| Technology principle of operation | Lateral flow immunoassay | Same |
| Assay targets | Influenza A and B nucleoprotein | Same |
| Assay results | Qualitative | Same |
| Intended Use | The Sofia Influenza A+B FIA employs immunofluorescence to detect influenza A and influenza B viral nucleoprotein antigens in nasal swab, nasopharyngeal swab, and nasopharyngeal aspirate/wash in fresh or transport media specimens from symptomatic patients. This qualitative test is intended for use as an aid in the rapid differential diagnosis of acute influenza A and influenza B viral infections. The test is not intended to detect influenza C antigens. A | The Sofia Influenza A+B FIA employs immunofluorescence to detect influenza A and influenza B viral nucleoprotein antigens in direct nasal swab, nasopharyngeal swab, and nasopharyngeal aspirate/wash specimens and nasopharyngeal swab and nasopharyngeal aspirate/wash specimens in transport media from symptomatic patients. This qualitative test is intended for use as an aid in the rapid differential diagnosis of acute influenza A and |

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| Similarities and Differences | | |
| --- | --- | --- |
| | Predicate Device | Proposed Device |
| Item | Sofia Influenza A+B FIA on Sofia (K153012) | Sofia Influenza A+B FIA on Sofia 2 (K162438) |
| | negative test is presumptive and it is recommended these results be confirmed by virus culture or an FDA-cleared influenza A and B molecular assay. Negative results do not preclude influenza virus infections and should not be used as the sole basis for treatment or other management decisions. The test is intended for professional and laboratory use.

Performance characteristics for influenza A and B were established during February through March 2011 when influenza viruses A/California/7/2009 (2009 HINI), A/Perth/16/2009 (H3N2), and B/Brisbane/60/2008 (Victoria-Like) were the predominant influenza viruses in circulation according to the Morbidity and Mortality Weekly Report from the CDC entitled "Update: Influenza Activity--United States, 2010-2011 Season, and Composition of the 2011-2012 Influenza Vaccine". Performance characteristics may vary against other emerging influenza viruses.

If infection with a novel influenza 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. Virus culture should not be | influenza B viral infections. The test is not intended to detect influenza C antigens. A negative test is presumptive and it is recommended these results be confirmed by viral culture or an FDA-cleared influenza A and B molecular assay. Negative results do not preclude influenza virus infections and should not be used as the sole basis for treatment or other patient management decisions. This test is intended for professional and laboratory use.

The Sofia Influenza A+B FIA may be used with Sofia or Sofia 2.

Performance characteristics for influenza A and B were established during February through March 2011 when influenza viruses A/California/7/2009 (2009 H1N1), A/Perth/16/2009 (H3N2), and B/Brisbane/60/2008 (Victoria-Like) were the predominant influenza viruses in circulation according to the Morbidity and Mortality Weekly Report from the CDC entitled “Update: Influenza Activity--United States, 2010-2011 Season, and Composition of the 2011-2012 Influenza Vaccine.” Performance characteristics may vary against other emerging influenza viruses.

If infection with a novel influenza virus is suspected based on current clinical and epidemiological screening criteria recommended by public health authorities, samples |

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| Similarities and Differences | | |
| --- | --- | --- |
| | Predicate Device | Proposed Device |
| Item | Sofia Influenza A+B FIA on Sofia (K153012) | Sofia Influenza A+B FIA on Sofia 2 (K162438) |
| | attempted in these cases unless a BSL 3+ facility is available to receive and culture 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 samples. |
| Specimen types | NS, NP, and NA/W specimens both direct and in VTM | NS, NP, and NA/W direct specimens and NP and NA/W in VTM |
| Internal assay controls | Negative control line, procedural control zone and reference line | Same |
| External controls | Test kit contains positive and negative control swab | Same |
| Instrument | Sofia | Sofia 2 |
| Dimensions | 24 cm x 16 cm x 10 cm | 19.7 cm x 11.4 cm x 12.7cm |
| Weight | 3 lbs | ~2.5 lbs |
| Power supply | 100-240 VAC, self-switching, or with 4 AA batteries | 100-240 VAC, self-switching, or with rechargeable lithium polymer battery |
| Printer | Integrated | External |
| Assay/instrument interface | Drawer | Same |
| User interface | 3.5 inch diagonal color LCD display and numeric keypad with function specific buttons touchscreen display | 4 inch color LCD touchscreen display |
| Sample ID | External hand-held barcode scanner | Integrated barcode scanner |
| Cassette ID | Integrated barcode scanner | Integrated barcode scanner with custom 0.3MP camera |
| Development Modes | Two assay development modes: Walk Away and Read Now | Same |
| Time to obtain results | 15 minutes | Potential for early read in Walk-Away Mode. Sofia 2 will image cassette at 3, 5, 8, 10, and 15 minutes until a positive result is obtained. |

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K. Standard/Guidance Document Referenced (if applicable):

1. Evaluation of Detection Capability for Clinical Laboratory Measurement Procedures. EP17-A2: Approved Guideline-Second Edition 2012.

L. Test Principle:

See decision summary for K153012; the FDA-cleared Sofia Influenza A+B FIA has not been modified and it is compatible with the newly developed Sofia 2 analyzer.

M. Performance Characteristics

Limit of detection, reproducibility, assay precision, early read, and method comparison studies were conducted to demonstrate equivalent performance of the Sofia Influenza A+B FIA on the Sofia and Sofia 2 analyzers. Results from each of these studies are described below. Additional analytical and clinical performance data for the Sofia Influenza A+B FIA is available under K153012.

1. Analytical Performance

a. Limit of Detection

The limit of detection (LoD) of the Sofia Influenza A+B FIA was established on both the Sofia and Sofia 2 analyzers. The study included two influenza A and two influenza B virus strains spiked into negative clinical nasal swab matrix, and was designed to follow the approach outlined in CLSI document EP17-A2, entitled “Evaluation of Detection Capability for Clinical Laboratory Measurement Procedures.”

Briefly, an initial range finding study was conducted in which each of the four influenza virus strains was prepared at two different concentrations using the negative clinical matrix pool and tested in replicates of five with two lots of devices on each of the two instrument platforms (Sofia and Sofia 2). For each strain, the lowest dilution yielding all five positive results was then used as the starting concentration for two-fold serial dilutions. The lowest dilution yielding all 10 positive results was defined as the preliminary LoD.

Additional 60 replicates of each virus strain at the preliminary LoD were tested on each of the two lots on each instrument platform. Testing spanned three days with at least 20 replicates run per day for each strain, lot and instrument combination.

The results of the LoD study are shown in Table 1 below.

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Table 1: Sofia Influenza A+B FIA LoD Study Results on the Sofia and Sofia 2 Analyzers

| Viral Strain | Platform | LoD (TCID50/mL) |
| --- | --- | --- |
| A/California/07/2009 | Sofia | 5.48 |
| | Sofia 2 | 9.79 |
| A/Hong Kong/8/68 | Sofia | 1.80 |
| | Sofia 2 | 2.19 |
| B/Allen/45 | Sofia | 113 |
| | Sofia 2 | 82.3 |
| B/Malaysia/2506/04 | Sofia | 8.37 |
| | Sofia 2 | 8.37 |

The newly established LoDs (using a new preparation of the viral strains) for the Sofia Influenza A+B FIA on the Sofia and Sofia 2 analyzers differ by less than two-fold, indicating that the LoD generated on each of the two instruments is similar.

# b. Reproducibility

The reproducibility of the Sofia Influenza A+B FIA on Sofia 2 analyzer was evaluated at three different laboratories. Two to three different operators at each site blindly tested a series of coded, contrived samples, prepared in negative nasal swab matrix, ranging from negative to moderate positive influenza A and influenza B. The influenza strains used were inactivated Influenza A/Hong Kong/8/68 and Influenza B/Allen/45. Testing of the same panel was also performed in parallel with Sofia in order to collect comparison data. Each operator at three study sites tested a 15-member reproducibility panel on both the Sofia and Sofia 2 analyzers once per day on 5 different days totaling 150 tests per each of the three testing sites for a total of 450 samples. The study was conducted in the Read Now mode.

The percent agreement between the expected results and the reproducibility study results for the Sofia and Sofia 2 analyzers for each analyte concentration tested is shown in Tables 2 and 3, respectively.

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Table 2: Qualitative Reproducibility Study Results Using the Sofia Analyzer

| Site | Operator | Influenza A+B Negative | Influenza A Low Positive (1X LoD) | Influenza A Moderate Positive (2-3X LoD) | Influenza B Low Positive (1X LoD) | Influenza B Moderate Positive (2-3X LoD) |
| --- | --- | --- | --- | --- | --- | --- |
| 1 | 1 | 15/15 | 15/15 | 15/15 | 15/15 | 15/15 |
| | 2 | 3/3 | 3/3 | 3/3 | 3/3 | 3/3 |
| | 3 | 12/12 | 12/12 | 12/12 | 12/12 | 12/12 |
| 2 | 1 | 15/15 | 15/15 | 15/15 | 15/15 | 15/15 |
| | 2 | 15/15 | 15/15 | 15/15 | 15/15 | 15/15 |
| 3 | 1 | 14*/15 | 15/15 | 15/15 | 15/15 | 14*/15 |
| | 2 | 15/15 | 15/15 | 15/15 | 15/15 | 15/15 |
| Combined Total | | 89/90 | 90/90 | 90/90 | 90/90 | 89/90 |
| Percent Agreement (95% CI) | | 98.9% (93.9-99.8%) | 100% (95.9-100%) | 100% (95.9-100%) | 100% (95.9-100%) | 98.9% (93.9-99.8%) |

* The discordant result for the Negative and the 2-3X samples appeared to be a mix-up at the site as the samples were tested on the same day by the same operator

Table 3: Qualitative Reproducibility Study Results Using the Sofia 2 Analyzer

| Site | Operator | Influenza A+B Negative | Influenza A Low Positive (1X LoD) | Influenza A Moderate Positive (2-3X LoD) | Influenza B Low Positive (1X LoD) | Influenza B Moderate Positive (2-3X LoD) |
| --- | --- | --- | --- | --- | --- | --- |
| 1 | 1 | 15/15 | 15/15 | 15/15 | 15/15 | 15/15 |
| | 2 | 3/3 | 3/3 | 3/3 | 3/3 | 3/3 |
| | 3 | 12/12 | 12/12 | 12/12 | 12/12 | 12/12 |
| 2 | 1 | 15/15 | 15/15 | 15/15 | 15/15 | 15/15 |
| | 2 | 15/15 | 15/15 | 15/15 | 15/15 | 15/15 |
| 3 | 1 | 14*/15 | 15/15 | 15/15 | 15/15 | 14*/15 |
| | 2 | 15/15 | 15/15 | 15/15 | 15/15 | 15/15 |
| Combined Total | | 89/90 | 90/90 | 90/90 | 90/90 | 89/90 |
| Percent Agreement (95% CI) | | 98.9% (93.9-99.8%) | 100% (95.9-100%) | 100% (95.9-100%) | 100% (95.9-100%) | 98.9% (93.9-99.8%) |

* The discordant result for the Negative and the 2-3X samples appeared to be a mix-up at the site as the samples were tested on the same day by the same operator

For each analyte concentration levels listed above, the mean relative fluorescence units (RFU), standard deviation (SD), and percent coefficient of variation (% CV) were calculated. Results for samples tested using the Sofia and Sofia 2 analyzers are shown in Tables 4 and 5 below.

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Table 4: RFU-based Reproducibility Results Using the Sofia Analyzer

| Sample Type | Site | Mean RFU | | SD | | % CV | |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Influenza A+B Negative | | A | B | A | B | A | B |
| | 1 | 543 | 794 | 95 | 104 | 17.5 | 13.1 |
| | 2 | 699 | 862 | 85 | 108 | 12.1 | 12.5 |
| | 3 | 678 | 1,300 | 95 | 133 | 14.1 | 10.3 |
| | Average | 640 | 985 | 92 | 115 | 14.6 | 12.0 |
| Influenza A Low Positive (1X LoD) | 1 | 4,757 | | 847 | | 17.8 | |
| | 2 | 5,616 | | 596 | | 10.6 | |
| | 3 | 5,581 | | 1,611 | | 28.9 | |
| | Average | 5,318 | | 1,018 | | 19.1 | |
| Influenza A Moderate Positive (2-3X LoD) | 1 | 11,173 | | 2,233 | | 20.0 | |
| | 2 | 13,979 | | 1,752 | | 12.5 | |
| | 3 | 11,847 | | 2,992 | | 25.3 | |
| | Average | 12,333 | | 2,326 | | 19.3 | |
| Influenza B Low Positive (1X LoD) | 1 | 8,430 | | 1,533 | | 18.4 | |
| | 2 | 10,366 | | 1,036 | | 10.0 | |
| | 3 | 8,343 | | 1,583 | | 19.0 | |
| | Average | 9,046 | | 1,391 | | 15.8 | |
| Influenza B Moderate Positive (2-3X LoD) | 1 | 10,469 | | 2,305 | | 22.0 | |
| | 2 | 12,806 | | 1,325 | | 10.3 | |
| | 3 | 9,761 | | 2,039 | | 20.9 | |
| | Average | 11,012 | | 1,890 | | 17.8 | |

Table 5: RFU-based Reproducibility Results Using the Sofia 2 Analyzer

| Sample Type | Site | Mean RFU | | SD | | % CV | |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Influenza A+B Negative | | A | B | A | B | A | B |
| | 1 | 552 | 722 | 114 | 274 | 20.7 | 38 |
| | 2 | 669 | 775 | 106 | 279 | 15.9 | 36 |
| | 3 | 659 | 1,028 | 107 | 491 | 16.2 | 47.8 |
| | Average | 626 | 841 | 109 | 348 | 17.6 | 40.6 |
| Influenza A Low Positive (1X LoD) | 1 | 4,109 | | 615 | | 15.0 | |
| | 2 | 5,620 | | 741 | | 13.2 | |
| | 3 | 5,631 | | 1,815 | | 32.2 | |
| | Average | 5,120 | | 1,057 | | 20.1 | |
| Influenza A Moderate Positive (2-3X LoD) | 1 | 10,051 | | 1,691 | | 16.8 | |
| | 2 | 14,224 | | 1,539 | | 10.8 | |
| | 3 | 12,007 | | 3,387 | | 28.2 | |
| | Average | 12,094 | | 2,206 | | 18.6 | |
| Influenza B Low Positive (1X LoD) | 1 | 7,178 | | 1,149 | | 16.0 | |
| | 2 | 10,366 | | 1,158 | | 11.2 | |
| | 3 | 8,750 | | 1,739 | | 19.9 | |
| | Average | 8,765 | | 1,348 | | 15.7 | |

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Although minor differences in the measured fluorescence were observed between the Sofia and Sofia 2 analyzers, no clinically significant difference was observed in the qualitative results; all clinical samples produced equivalent qualitative results. The interlaboratory qualitative agreement for Sofia Influenza A+B FIA with Sofia and Sofia 2 analyzers was equivalent and ranged from 98.9% to 100%. Similarly, the intra-laboratory qualitative agreement for Sofia Influenza A+B FIA with Sofia and Sofia 2 analyzers was found comparable and ranged from 98.7% to 100%.

c. Assay Precision

To supplement the reproducibility study, within-laboratory precision of the Sofia and Sofia 2 analyzers was evaluated. Influenza A/California/07/09 and influenza B/Malaysian/2506/04 strains were tested at two different analyte concentrations: a “low positive” sample with an analyte concentration approximately 1X LoD and a “moderate positive” sample with an analyte concentration 2- 3X LoD. One negative matrix sample was also included in the testing.

Five samples (negative, low positive (influenza A and B) and moderate positive (influenza A and B)) were tested on three lots of Sofia influenza A+B FIA cassettes, by two operators on 12 different days (1 sample x 3 reagent lots x 2 operators x 12 days) totaling 72 replicates per sample per instrument. The assay was run in Read Now mode on one Sofia analyzer and one Sofia 2 analyzer.

Overall percent agreement between the expected results and the precision study results for the Sofia and Sofia 2 analyzer is shown in Table 6 below.

Table 6: Qualitative Precision Study Results Summary

| Sample Type | Sofia | | Sofia 2 | |
| --- | --- | --- | --- | --- |
| | Overall Agreement | % Overall Agreement | Overall Agreement | % Overall Agreement |
| Negative A+B | 72/72 | 100 | 72/72 | 100 |
| Influenza A Low Positive (1X LoD) | 72/72 | 100 | 72/72 | 100 |
| Influenza A Moderate Positive (2-3X LoD) | 72/72 | 100 | 72/72 | 100 |
| Influenza B Low Positive (1X LoD) | 72/72 | 100 | 72/72 | 100 |
| Influenza B Moderate Positive (2-3X LoD) | 72/72 | 100 | 72/72 | 100 |

For each of the sample types listed above, the mean relative fluorescence units (RFU), standard deviation (SD), and percent coefficient of variation (%CV) were calculated. Results for samples tested using the Sofia and Sofia 2 analyzers are shown in Table 7.

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Table 7: RFU-based Precision Study Results Summary

| Platform | Sample Type | Mean RFU | SD | % CV |
| --- | --- | --- | --- | --- |
| Sofia | Negative Influenza A | 651.9 | 165.7 | 25.4 |
| | Negative Influenza B | 846.0 | 223.3 | 26.4 |
| | Influenza A Low Positive (1X LoD) | 4497.7 | 595.9 | 13.2 |
| | Influenza B Low Positive (1X LoD) | 4652.1 | 626.1 | 13.5 |
| | Influenza A Moderate Positive (2-3X LoD) | 9942.3 | 1460.1 | 14.7 |
| | Influenza B Moderate Positive (2-3X LoD) | 12201.5 | 1565.3 | 12.8 |
| Sofia 2 | Negative Influenza A | 582.6 | 149.3 | 25.6 |
| | Negative Influenza B | 425.5 | 440.4 | 103.5 |
| | Influenza A Low Positive (1X LoD) | 4283.4 | 590.9 | 13.8 |
| | Influenza B Low Positive (1X LoD) | 4480.7 | 593.2 | 13.2 |
| | Influenza A Moderate Positive (2-3X LoD) | 9649.1 | 1225.0 | 12.7 |
| | Influenza B Moderate Positive (2-3X LoD) | 11684.7 | 1548.0 | 13.2 |

Though a difference was observed between Sofia and Sofia 2 analyzers for negative influenza B samples, the qualitative result of the analyzers did not change and all negative samples were $100\%$ negative by both Sofia and Sofia 2 analyzers. Overall, the study results showed that Sofia and Sofia 2 analyzers generated clinically equivalent qualitative results when used by multiple operators, on multiple device lots, and operated over multiple days.

# d. Early Read

Additional study was performed to support the multi-read feature of the Sofia 2 analyzer in Walk Away mode i.e., the test cassettes were scanned and interpreted by the Sofia 2 analyzer at 3, 5, 8, 10, and 15 minutes. Positive samples were prepared using one strain each of influenza A (A/California/07/09) and influenza B (B/Malaysian/2506/04) spiked in M4-RT transport media. Negative samples were contrived with extraction reagent reconstituted with solutions of $0.2\%$ to $0.8\%$ mucin in $50\%$ M4-RT and M6 viral transport media in saline. The study results demonstrated that positive samples (depending on the viral load) can be interpreted as positive as early as 3 minutes with Sofia 2 in Walk Away mode.

# 2. Comparison Studies

# a. Method Comparison

A method comparison study using clinical samples was conducted to demonstrate comparable performance of the Sofia Influenza A+B FIA using the Sofia and Sofia 2 analyzers. The study was conducted at three sites testing identical specimen panels that consisted of 100 influenza A positive, 50 influenza B positive, and 100 influenza negative clinical samples. Each panel member was assigned to one of the analyte concentration levels based on the signal-to-cutoff ratio (S/CO) that was obtained from a single replicate on the Sofia analyzer. The Table 8 below shows the S/CO for each level.

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Table 7: S/CO Target Values

| Panel Member | Influenza A S/CO | Influenza B S/CO |
| --- | --- | --- |
| Negative | <0.5 | |
| High Negative | 0.75-0.95 | 0.75-0.95 |
| Low Positive (1X LoD) | 1.45-1.76 | 2.32-2.42 |
| Moderate Positive(2-3X LoD) | 3.0-5.1 | 4.64-6.96 |
| High Positive (4-5X LoD) | 6.5-8.5 | 9.28-11.6 |
| Very High Positive (>5X LoD) | >9 | >12 |

The final composition of the Method Comparison Panel was as follows in Table 9 below.

Table 9: Method Comparison Panel

| Panel Member | Quantity per panel |
| --- | --- |
| Negative for both influenza A and influenza B | 66 |
| High Negative for influenza A | 20 |
| High Negative for influenza B | 14 |
| Low Positive for influenza A (1X LoD) | 35 |
| Low Positive for influenza B (1X LoD) | 15 |
| Moderate Positive for influenza A (2-3X LoD) | 30 |
| Moderate Positive for influenza B (2-3X LoD) | 17 |
| High Positive for influenza A (4-5X LoD) | 15 |
| High Positive for influenza B (4-5X LoD) | 11 |
| Very High Positive for influenza A (>5X LoD) | 20 |
| Very High Positive for influenza A (>5X LoD) | 7 |

A total of 250 tests were performed at each of the three testing sites resulting in a total of 749 results (one specimen test result was not recoverable) across the three testing sites utilizing 15 Sofia and 14 Sofia 2 analyzers. To assess the potential for early read with Sofia 2, the testing for all specimens was conducted in Walk Away Mode. In this mode,

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Sofia 2 captured the images of each test cassette at 5, 8, and 15 minutes. The overall study results obtained after the full 15 minutes are shown in Tables 10 and 11 below. Agreement between the results obtained on the Sofia and Sofia 2 analyzers for each of the individual analyte levels tested is shown in Tables 12 and 13.

Table 10: Method Comparison Study Influenza A Results for the Sofia and Sofia 2 Analyzers

| | Sofia Positive | Sofia Negative | | |
| --- | --- | --- | --- | --- |
| Sofia 2 Positive | 304 | 15 | Positive % Agreement (95% CI) | 304/311=98% (95.4-98.9%) |
| Sofia 2 Negative | 7 | 423 | Negative % Agreement (95% CI) | 423/438=97% (94.4-97.9%) |

Table 11: Agreement Stratified by Influenza A Level

| Analyte Level | Qualitative Method Comparison Results | | |
| --- | --- | --- | --- |
| | | Sofia Positive | Sofia Negative |
| Negative | Sofia 2 Positive | 0 | 0 |
| | Sofia 2 Negative | 0 | 198 |
| High Negative | Sofia 2 Positive | 11 | 12 |
| | Sofia 2 Negative | 6 | 31 |
| Low Positive (1X LoD) | Sofia 2 Positive | 98 | 3 |
| | Sofia 2 Negative | 1 | 3 |
| Moderate Positive (2-3X LoD) | Sofia 2 Positive | 90 | 0 |
| | Sofia 2 Negative | 0 | 0 |
| High Positive (4-5X LoD) | Sofia 2 Positive | 45 | 0 |
| | Sofia 2 Negative | 0 | 0 |
| Strong Positive (>5X LoD) | Sofia 2 Positive | 60 | 0 |
| | Sofia 2 Negative | 0 | 0 |

Table 12: Method Comparison Study Influenza B Results for the Sofia and Sofia 2 Analyzers

| | Sofia Positive | Sofia Negative | | |
| --- | --- | --- | --- | --- |
| Sofia 2 Positive | 154 | 5 | Positive % Agreement (95% CI) | 154/157=98% (94.5-99.4%) |
| Sofia 2 Negative | 3 | 587 | Negative % Agreement (95% CI) | 587/592=99% (98.1-99.6%) |

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Table 13: Agreement Stratified by Influenza B Level

| Analyte Level | Qualitative Method Comparison Results | | |
| --- | --- | --- | --- |
| | | Sofia Positive | Sofia Negative |
| Negative | Sofia 2 Positive | 0 | 0 |
| | Sofia 2 Negative | 0 | 198 |
| High Negative | Sofia 2 Positive | 5 | 5 |
| | Sofia 2 Negative | 3 | 29 |
| Low Positive (1X LoD) | Sofia 2 Positive | 45 | 0 |
| | Sofia 2 Negative | 0 | 0 |
| Moderate Positive (2-3X LoD) | Sofia 2 Positive | 50 | 0 |
| | Sofia 2 Negative | 0 | 0 |
| High Positive (4-5X LoD) | Sofia 2 Positive | 33 | 0 |
| | Sofia 2 Negative | 0 | 0 |
| Strong Positive (>5X LoD) | Sofia 2 Positive | 21 | 0 |
| | Sofia 2 Negative | 0 | 0 |

The method comparison study results demonstrate that the performance of the Sofia Influenza A+B FIA on the Sofia 2 is comparable to the predicate device. There were 22 discordant results for influenza A and 8 discordant results for influenza B across all the three sites. Eighteen samples of the 22 discordant influenza A results were categorized as "high negative" and four samples were characterized as "Low positive (1X LoD)". All eight influenza B discordant results were characterized as "high negative". These discordant results were observed across all three sites and were generated by multiple operators, no trend indicating any instrument bias was observed.

For influenza A specimens, 100% of the specimens yielded positive results by 8 minutes and at least 91% by 5 minutes at ≥2-3X LoD; more than 80% were positive by 8 minutes at 1X LoD. For influenza B specimens, 100% of the specimens yielded positive results by 5 minutes at ≥2-3X LoD; 89% were positive by 5 minutes and 100% were positives by 8 minutes at 1X LoD.

## N. Instrumentation/System Description

1. Instrument Name:
Sofia and Sofia 2

2. System Description:
The Sofia instruments are equipped with UV LED lighting and optical detection systems that are designed to collect and analyze fluorescent data emitted from the Sofia influenza

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A+B FIA test cassettes. The instrument software contains embedded assay-specific algorithms that are used to convert the fluorescent signal data into a qualitative test result.

3. Software:
FDA has reviewed applicant’s Hazard Analysis and software development processes for this line of product types.

Yes ☐ X or No ☐

4. Level of Concern
Moderate

5. Software Description
The Sofia 2 Analyzer images the test strip and utilizes an embedded software algorithm to process the resulting data set into a qualitative test result. A positive test result for the analyte is determined by detection and analysis of the fluorescent signal at the test and reference lines, which are processed by the assay-specific algorithm. The algorithm employs a smoothing filter to the data and, identifies a peak maxima, minima and width, then calculates the RFU value based on peak height for the analyte test line. Results are presented on a screen and can be printed on an integrated printer.

6. Specimen Identification
Each cassette is labeled with a barcode that is detected by the Sofia 2 internal barcode reader. The 2-dimensional barcode contains lot, expiration, and test method information. If the cassette is not in the correct orientation, the barcode cannot be read and the analyzer will display an error.

7. Calibration
To ensure that signal drift is controlled, the Sofia 2 analyzer has a calibration algorithm that reminds the operator to check the calibration status of the instrument every 30 days. The calibration cassette uses a highly stable fluorescent reagent along with a unique barcode. The insertion of this cassette triggers the Sofia 2 analyzer to self-check its calibration.

O. Other supportive Instrument Characteristics Data Not Covered in the “Performance Characteristics” Section Above
N/A

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P. Proposed Labeling

The labeling is sufficient and it satisfies the requirements of 21 CFR Part 809.10.

Q. Conclusion

The submitted information in the premarket notification is complete and supports a substantial equivalence decision.

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