← Product Code [PSZ](/submissions/MI/subpart-d%E2%80%94serological-reagents/PSZ) · K041049

# BINAXNOW INFLUENZA A & B TEST (K041049)

_Binax, Inc. · PSZ · Aug 10, 2004 · Microbiology · SESE_

**Canonical URL:** https://fda.innolitics.com/submissions/MI/subpart-d%E2%80%94serological-reagents/PSZ/K041049

## Device Facts

- **Applicant:** Binax, Inc.
- **Product Code:** [PSZ](/submissions/MI/subpart-d%E2%80%94serological-reagents/PSZ.md)
- **Decision Date:** Aug 10, 2004
- **Decision:** SESE
- **Submission Type:** Traditional
- **Regulation:** 21 CFR 866.3328
- **Device Class:** Class 2
- **Review Panel:** Microbiology
- **Attributes:** Pediatric

## Intended Use

The BinaxNOW® Influenza A & B Test is an in vitro immunochromatographic assay for the qualitative detection of influenza A and B nucleoprotein antigens in nasopharyngeal swab and nasal wash/aspirate specimens. It is intended to aid in the rapid differential diagnosis of influenza A and B viral infections. Negative test results should be confirmed by culture.

## Device Story

The BinaxNOW® Influenza A & B Test is an immunochromatographic membrane assay used in clinical settings to detect influenza A and B nucleoprotein antigens. Input consists of nasopharyngeal swabs or nasal wash/aspirate specimens. The sample is eluted into a solution and applied to a test strip housed in a book-shaped hinged cardboard device. The strip contains immobilized monoclonal antibodies that capture viral antigens; a blue control line confirms assay validity. Results are interpreted visually by a clinician or technician at 15 minutes based on the presence of pink-to-purple sample lines. The test provides rapid differential diagnosis, aiding clinical decision-making for patient management. Visibly bloody samples are contraindicated due to potential interference.

## Clinical Evidence

Clinical performance was evaluated in a multi-site prospective study and retrospective frozen sample analysis. The study included 306 retrospective samples for Flu A and 303 for Flu B, representing diverse patient demographics (64% pediatric, 36% adult). Compared to individual predicate tests, the device demonstrated 100% sensitivity and 96% specificity for Influenza A, and 93% sensitivity and 97% specificity for Influenza B. Reproducibility studies across three sites showed 97% agreement. Analytical sensitivity (LOD) was established using inactivated viral strains. No clinical data regarding patient outcomes was provided; performance is based on diagnostic accuracy against predicate devices and viral culture.

## Technological Characteristics

Lateral flow immunochromatographic membrane assay. Components: monoclonal antibodies, membrane support, cardboard hinged test device. Sample preparation: elution solution, saline, or transport media. Visual interpretation of colored lines. No electronic components, software, or external energy source required.

## Regulatory 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

- FLU OIA A/B Test Kit ([K021469](/device/K021469.md))

## Submission Summary (Full Text)

> This content was OCRed from public FDA records by [Innolitics](https://innolitics.com). If you use, quote, summarize, crawl, or train on this content, cite Innolitics at https://innolitics.com.
>
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# 510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY DEVICE ONLY TEMPLATE

A. 510(k) Number: K041049

B. Purpose for Submission: New device clearance

C. Analyte: Influenza Type A nucleoprotein antigens

D. Type of Test: Lateral flow immunochromatographic assay

E. Applicant: Binax, Inc.

F. Proprietary and Established Names: BinaxNOW Influenza A & B

G. Regulatory Information:

1. Regulation section: 21 CFR Part 866.3330
2. Classification: Antigens, CF (including CF Control), Influenza virus A, B, C
3. Product Code: GNX
4. Panel: 83 Microbiology

H. Intended Use:

1. Intended use(s):

The BinaxNOW® Influenza A & B Test is an in vitro immunochromatographic assay for the qualitative detection of influenza A and B nucleoprotein antigens in nasopharyngeal (NP) swab and nasal wash/aspirate specimens. It is intended to aid in the rapid differential diagnosis of influenza A and B viral infections. Negative test results should be confirmed by cell culture.

Caution: Assay sensitivity was determined primarily using archived specimens. Users may wish to establish the sensitivity of this test on fresh samples.

2. Indication(s) for use: NA

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3. Special condition for use statement(s): The device is for prescription use only
4. Special instrument Requirements: NA

I. Device Description:

The BinaxNOW® Influenza A & B Test is an immunochromatographic membrane assay that uses highly sensitive monoclonal antibodies to detect influenza type A and B nucleoprotein antigens in NP specimens. These antibodies and a control antibody are immobilized onto a membrane support as three distinct lines and combined with other reagents/pads to construct a test strip. This test strip is mounted inside a cardboard, book-shaped hinged test device.

Swab specimens require a sample preparation step, in which the sample is eluted off the swab into elution solution, saline or transport media. Nasal wash/aspirate samples require no preparation. Sample is added to the top of the test strip and the test device is closed. Test results are interpreted at 15 minutes based on the presence or absence of pink-to-purple colored Sample Lines. The blue Control Line turns pink in a valid assay.

J. Substantial Equivalence Information:

1. Predicate device name(s): FLU OIA A/B Test Kit manufactured by Thermo Biostar Inc..
2. Predicate K number(s): K021469
3. Comparison with predicate:

Performance of the BinaxNOW® Influenza A & B Test was compared to the current NOW® Flu A Test on 306 retrospective frozen clinical samples and to the NOW® Flu B Test on 303 retrospective frozen clinical samples. All clinical samples were collected from symptomatic patients at multiple physician offices, clinics and hospitals located in the Southern, Northeastern and Midwestern regions of the United States and from one hospital in Sweden. Fifty-three percent (53%) of the population tested was male, 47% female, 64% pediatric (< 18 years) and 36% adult (≥ 18 years). Nasal wash/aspirate specimens comprised approximately 57% of the samples tested, while NP swabs represented 42%. No differences in test performance were observed based on patient age and gender or based on sample type tested.

The BinaxNOW® Influenza A & B Test was 100% sensitive and 96% specific for detection of influenza A vs. the NOW® Flu A Test and 93% sensitive and 97% specific for detection of influenza B vs. the NOW® Flu B Test.

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

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# L. Test Principle:

Performance of the BinaxNOW® Influenza A & B Test was compared to the current NOW® Flu A Test on 306 retrospective frozen clinical samples and to the NOW® Flu B Test on 303 retrospective frozen clinical samples. All clinical samples were collected from symptomatic patients at multiple physician offices, clinics and hospitals located in the Southern, Northeastern and Midwestern regions of the United States and from one hospital in Sweden. Fifty-three percent (53%) of the population tested was male, 47% female, 64% pediatric (< 18 years) and 36% adult (≥ 18 years). Nasal wash/aspirate specimens comprised approximately 57% of the samples tested, while NP swabs represented 42%. No differences in test performance were observed based on patient age and gender or based on sample type tested.

The BinaxNOW® Influenza A & B Test was 100% sensitive and 96% specific for detection of influenza A vs. the NOW® Flu A Test and 93% sensitive and 97% specific for detection of influenza B vs. the NOW® Flu B Test. Test performance by virus type (A vs. B), by sample type (swab vs. wash/aspirate), and overall, including 95% confidence intervals, is detailed in the following tables.

# M. Performance Characteristics (if/when applicable):

1. Analytical performance:

a. Precision/Reproducibility:

A blind study of the BinaxNOW® Influenza A & B Test was conducted at 3 separate sites using panels of blind coded specimens containing negative, low positive, and moderate positive samples. Participants tested each sample multiple times on 3 different days. There was 97% (242/250) agreement with expected test results, with no significant differences within run (replicates tested by one operator), between run (3 different days), between sites (3 sites), or between operators (6 operators).

a. Linearity/assay reportable range:

NA

b. Traceability, Stability, Expected values (controls, calibrators, or method):

NA

c. Detection limit:

The BinaxNOW® test limit of detection (LOD), defined as the concentration of influenza virus that produces positive BinaxNOW® test results approximately 95% of the time, was identified by evaluating different concentrations of inactivated Flu A/Beijing and inactivated Flu B/Harbin in the BinaxNOW® test.

Twelve (12) different operators each interpreted 2 devices run at each concentration for a total of 24 determinations per level. The following results identify a concentration of 1.03 x 10² ng/ml as the LOD for Flu A/Beijing and 6.05 x 10¹ ng/ml for Flu B/Harbin.

d. Assay cut-off:

NA

2. Comparison studies:

a. Method comparison with predicate device:

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See J.3 above

## b. Matrix comparison:

NA

### 3. Clinical studies:

#### a. Clinical sensitivity:

Performance of the Binax NOW® Flu A and Flu B Tests was compared to cell culture on 373 prospective clinical samples collected as part of a multi-center study conducted during the 2002 Flu season at physician offices and clinics located in the Western and mid-Atlantic United States. Fifty-four percent (54%) of the population tested was male, 46% female, 90% pediatric (< 18 years) and 10% adult (≥ 18 years). Nasal wash/aspirates comprised 51% of the samples tested, while NP swabs represented 49%. No differences in performance were observed based on patient age and gender or based on sample type tested.

The Binax NOW® Flu A Test was 80% sensitive and 93% specific while the Binax NOW® Flu B Test was 65% sensitive and 97% specific when compared to cell culture. The performance of the two tests by sample type (swab vs. wash/aspirate) and overall, including 95% confidence intervals, is detailed in the following tables.

#### b. Clinical specificity:

The performance of the BinaxNOW® Influenza A & B Test was compared to cell culture and/or DFA, and to the Binax NOW® Flu A Test and the Binax NOW® Flu B Test, in a prospective study conducted in 2004 outside the US. Nasopharyngeal (NP) swab and nasal wash / aspirate specimens, collected at multiple sites from children (less than 18 years of age) and adults (18 years or older) presenting with influenza-like symptoms, were evaluated in the Binax test at a central testing lab.

Forty-seven percent (47%) of the population tested was male, 53% female, 40% pediatric (< 18 years), and 60% adult (≥ 18 years). No differences in test performance were observed based on patient age or gender. There were no invalid tests reported.

One hundred and thirteen (113) NP swab specimens and 1 wash/aspirate specimen were tested. One hundred and eight (108) of the 114 samples tested were influenza negative by culture/DFA, and 6 samples were influenza positive. When compared to culture/DFA, the BinaxNOW® Test was 75% (3/4) sensitive and 100% (110/110) specific for detection of influenza A and 50% (1/2) sensitive and 100% (112/112) specific for detection of influenza B. There was 100% agreement between the BinaxNOW® Influenza A & B Test and the individual Flu A and Flu B Tests.

BinaxNOW® A & B Test specificity by sample type versus cell culture / DFA, including 95% confidence intervals, is listed below.

#### c. Other clinical supportive data (when a and b are not applicable):

4. Clinical cut-off:
NA

5. Expected values/Reference range:

#### Expected Values

The prevalence of influenza varies from year to year, with outbreaks typically occurring during the fall and winter months. The rate of positivity found in influenza testing is dependent on many factors including the method of specimen collection, the test method

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used, geographic location, and the disease prevalence in specific localities. Type A viruses are typically associated with most serious influenza epidemics, while Type B are typically milder. In a multi-center clinical study conducted by Binax in the U.S. during the 2002 influenza season, the average prevalence of influenza A (as determined by viral cell culture) was 26% in nasal wash samples and 20% in NP swab samples. The average prevalence of influenza B was 21% in nasal wash samples and 20% in NP swab samples.

N. Conclusion:
The submitted material in this premarket notification is complete and supports a substantial equivalence decision.

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**Source:** [https://fda.innolitics.com/submissions/MI/subpart-d%E2%80%94serological-reagents/PSZ/K041049](https://fda.innolitics.com/submissions/MI/subpart-d%E2%80%94serological-reagents/PSZ/K041049)

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