(27 days)
The Focus Diagnostics Simplexa™ Flu A/B & RSV Direct assay is intended for use on the 3M Integrated Cycler instrument for the in vitro qualitative detection and differentiation of influenza B virus, and respiratory syncytial virus (RSV) RNA in nasopharyngeal swabs (NPS) from human patients with signs and symptoms of respiratory tract infection in conjunction with clinical and epidemiological risk factors. This test is intended for use as an aid in the differential diagnosis of influenza B, and RSV viral infections in humans and is not intended to detect influenza C.
Negative results do not preclude influenza virus or RSV infection and should not be used as the sole basis for treatment or other patient management decisions.
Performance characteristics for influenza A were established with clinical specimens collected during the 2010/2011 influenza season when 2009 H1N1 influenza and H3N2 were the predominant influenza A viruses 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 the 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.
Focus Diagnostics' Simplexa™ Flu A/B & RSV Positive Control Pack is intended to be used as a control with the Simplexa™ Flu A/B & RSV Direct kit. This control is not intended for use with other assays or systems.
The Simplexa™ Flu AB & RSV Direct assay system is a real-time RT-PCR system that enables the direct amplification, detection and differentiation of human influenza A (Flu A) virus RNA, human influenza B (Flu B) virus RNA and RSV RNA from unprocessed nasopharyngeal swabs that have not undergone nucleic acid extraction. The system consists of the Simplexa™ Flu A/B & RSV Direct assay, the 3M Integrated Cycler (with Integrated Cycler Studio Software), the Direct Amplification Disc and associated accessories.
In the Simplexa™ Flu A/B & RSV Direct assay, bi-functional fluorescent probe-primers are used together with corresponding reverse primers to amplify Flu A, Flu B, RSV and internal control RNA. The assay provides three results; conserved regions of influenza A viruses (matrix gene), influenza B viruses (matrix gene) and RSV (M gene) are targeted to identify these viruses in the specimen. An RNA internal control is used to detect RT-PCR failure and/or inhibition.
Here's a summary of the acceptance criteria and the study information for the Simplexa™ Flu A/B & RSV Direct device, based on the provided document:
Acceptance Criteria and Device Performance Study
The purpose of this Special 510(k) (K152408) is to expand the analytical reactivity of the Simplexa™ Flu A/B & RSV Direct assay to include 53 additional strains. Therefore, the primary acceptance criteria for this specific submission relate to the successful detection of these new strains.
1. Table of Acceptance Criteria and Reported Device Performance
The core acceptance criterion for the additional strains is detection by the Simplexa™ Flu A/B & RSV Direct assay. All tested strains were successfully detected.
| Target Organism | Acceptance Criteria | Reported Device Performance |
|---|---|---|
| Influenza A Viruses (37 strains) | Flu A Detected | All 37 tested Influenza A strains were detected. |
| Influenza B Viruses (9 strains) | Flu B Detected | All 9 tested Influenza B strains were detected. |
| RSV Viruses (7 strains) | RSV Detected | All 7 tested RSV strains were detected. |
Note: The document explicitly states: "Fifty-three strains met the established acceptance criteria and passed validation testing. Analytical Reactivity will be expanded to add 53 additional strains." This confirms that the acceptance criteria for these specific strains was successful detection.
2. Sample Size Used for the Test Set and Data Provenance
- Test Set Sample Size: For each of the 53 additional strains, the testing was performed in triplicate. This means a total of 53 strains * 3 replicates = 159 individual tests were performed for this specific analytical reactivity study.
- Data Provenance: The strains were sourced from various locations and historical periods, indicating a focus on analytical validity and strain diversity rather than clinical performance from a specific population or region. Examples include strains like "A/California/4/2009", "A/Massachusetts/15/2013", "A/Japan/305/57", "B/Brisbane/33/2008", and "ATCC-2012-10". The study itself is an analytical study conducted in a lab setting, not a direct clinical study. The document doesn't specify the country of origin where the testing took place, but it's likely a controlled lab environment.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications
This study focuses on analytical reactivity, where the "ground truth" is the presence and identification of a specific viral strain at a known concentration. This type of ground truth does not typically involve expert clinical adjudication. The ground truth (i.e., confirmation of the viral strain and its concentration) would have been established by standard laboratory methods for viral culture, quantification (e.g., TCID50/mL, CEID50/mL, PFU/mL), and characterization, prior to being used in the Simplexa™ assay. The document does not specify the number or qualifications of experts involved in establishing this initial ground truth, as it's a standard process in virology.
4. Adjudication Method for the Test Set
No adjudication method (e.g., 2+1, 3+1) is described, as this is an analytical study evaluating device performance against known quantities of target analytes, not a clinical study requiring human interpretation or consensus for diagnosis. The "result" is the output of the RT-PCR system ("Flu A Detected," "Flu B Detected," "RSV Detected").
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No MRMC comparative effectiveness study was done for this particular submission. This 510(k) is a "Special 510(k)" to expand analytical reactivity, not to re-evaluate or compare clinical effectiveness with human readers. The clinical performance characteristics were established in a previous submission (K142365).
6. Standalone Performance Study (Algorithm Only Without Human-in-the-Loop)
Yes, a standalone performance study was done for the analytical reactivity. The study evaluated the ability of the Simplexa™ Flu A/B & RSV Direct assay system (algorithm/device only) to detect the specified viral strains. The results presented ("Flu A Detected," "Flu B Detected," "RSV Detected") are direct outputs from the device, with no human intervention in the detection process itself.
7. Type of Ground Truth Used
The ground truth used for this analytical reactivity study was based on known quantified viral material. This means:
- Viral Culture/Quantification: Viral samples were quantified using methods like TCID50/mL (Tissue Culture Infectious Dose 50%), CEID50/mL (Chicken Embryo Infectious Dose 50%), PFU/mL (Plaque Forming Units/mL), or using purified RNA at known concentrations (e.g., ng/µL, IU/mL).
- Strain Identification: The specific identity and subtype of each viral strain were confirmed through standard virological methods.
- These known viral materials were then spiked into a negative swab matrix to simulate clinical samples for testing.
8. Sample Size for the Training Set
The document does not provide details about the training set sample size. This submission (K152408) is an expansion of analytical reactivity and refers to the predicate device K142365 for most other performance characteristics, including clinical studies. RT-PCR assays typically do not have a "training set" in the machine learning sense, but rather a development and validation process during which assay parameters are optimized and locked.
9. How the Ground Truth for the Training Set Was Established
Similar to point 8, the document does not specifically detail how a "training set ground truth" was established, as it's not a machine learning algorithm in the typical sense that would require a distinct training phase with labeled data in the way, for example, an image recognition AI would. The development of an RT-PCR assay involves optimization and validation studies using characterized viral isolates and clinical samples, where the "ground truth" for these samples is derived from:
- Reference Methods: Such as viral culture, sequencing, or other FDA-cleared assays.
- Expert Consensus: For clinical samples, expert microbiologists or virologists would confirm the presence/absence of target viruses using gold standard methods.
The current document focuses singularly on the analytical reactivity towards an expanded panel of viral strains, relying on the already established methodologies from the predicate device (K142365) for other aspects of performance.
§ 866.3980 Respiratory viral panel multiplex nucleic acid assay.
(a)
Identification. A respiratory viral panel multiplex nucleic acid assay is a qualitative in vitro diagnostic device intended to simultaneously detect and identify multiple viral nucleic acids extracted from human respiratory specimens or viral culture. The detection and identification of a specific viral nucleic acid from individuals exhibiting signs and symptoms of respiratory infection aids in the diagnosis of respiratory viral infection when used in conjunction with other clinical and laboratory findings. The device is intended for detection and identification of a combination of the following viruses:(1) Influenza A and Influenza B;
(2) Influenza A subtype H1 and Influenza A subtype H3;
(3) Respiratory Syncytial Virus subtype A and Respiratory Syncytial Virus subtype B;
(4) Parainfluenza 1, Parainfluenza 2, and Parainfluenza 3 virus;
(5) Human Metapneumovirus;
(6) Rhinovirus; and
(7) Adenovirus.
(b)
Classification. Class II (special controls). The special controls are:(1) FDA's guidance document entitled “Class II Special Controls Guidance Document: Respiratory Viral Panel Multiplex Nucleic Acid Assay;”
(2) For a device that detects and identifies Human Metapneumovirus, FDA's guidance document entitled “Class II Special Controls Guidance Document: Testing for Human Metapneumovirus (hMPV) Using Nucleic Acid Assays;” and
(3) For a device that detects and differentiates Influenza A subtype H1 and subtype H3, FDA's guidance document entitled “Class II Special Controls Guidance Document: Testing for Detection and Differentiation of Influenza A Virus Subtypes Using Multiplex Nucleic Acid Assays.” See § 866.1(e) for the availability of these guidance documents.