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510(k) Data Aggregation
(29 days)
The BD Directigen™ EZ Flu A+B test is a rapid chromatographic immunoassay for the direct and qualitative detection of influenza A and B viral antigens from nasopharyngeal washes/aspirates, nasopharyngeal swabs and throat swabs of symptomatic patients. The Directigen™ EZ Flu A+B test is a differentiated test, such that influenza A viral antigens can be distinguished from influenza B viral antigens from a single processed sample using a single device. The test is to be used as an aid in the diagnosis of influenza A and B viral infections. All negative test results should be confirmed by cell culture because negative results do not preclude influenza virus infection and should not be used as the sole basis for treatment or other management decisions.
The Directigen EZ Flu A+B test is a chromatographic assay to qualitatively detect influenza A and B viral antigens in samples processed from respiratory specimens. When specimens are processed and added to the test device, influenza A or B viral antigens bind to anti-influenza antibodies conjugated to visualizing particles in the corresponding A and B test strips. The antigen-conjugate complex migrates across the test strip to the reaction area and is captured by the line of antibody on the membrane. to other result for influenza A is visualized as a reddish purple line at the Test "T" position and the Control "C" position in the Directigen EZ Flu A read window. A positive result for influenza B is visualized as a reddish purple line at the Test "T" position and the Control "C" position in the Directigen EZ Flu B read window.
Here's an analysis of the provided text regarding the BD Directigen™ EZ Flu A+B test:
1. Table of Acceptance Criteria and Reported Device Performance
| Acceptance Criteria (Stated or Implied) | Reported Device Performance |
|---|---|
| Limit of Detection (LOD) for A/California/4/2009 (H1N1) | 3.5 Log10 TCID50/mL, equivalent to 5.37 x 10^2 TCID50/mL |
| Limit of Detection (LOD) for A/California/7/2009 (H1N1) | 3.5 Log10 TCID50/mL, equivalent to 1.86 x 10^3 TCID50/mL |
| Qualitative detection of influenza A and B viral antigens | The device showed reactivity with cultured strains of A/California/4/09 and A/California/7/09. (The document focuses on LOD for new strains, assuming general qualitative detection for previously cleared strains via substantial equivalence). A disclaimer was added: "although this test has been shown to detect the 2009 H1N1 virus cultured from a positive human respiratory specimen, the performance characteristics of this device with clinical specimens that are positive for the 2009 H1N1 influenza virus have not been established." |
| Ability to distinguish between influenza A and B viral antigens | The device differentiates influenza A from B (stated in Intended Use and Product Description). The study presented does not re-evaluate this specific differentiation; it focuses on H1N1 strain detection. |
| Substantial equivalence to predicate device (BD Directigen™ EZ Flu A+B) | The FDA determined the device is substantially equivalent to the predicate device. The additions made to the labeling (new strain data) did not change the intended use or fundamental scientific technology. |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size:
- For A/California/4/2009: Undiluted virus culture tested in triplicate. 10-fold dilutions tested in singlicate. Half-log dilutions prepared around the last positive 10-fold dilution and tested in triplicate.
- For A/California/7/2009: Undiluted virus culture tested in triplicate. 10-fold dilutions tested in singlicate. Half-log dilutions prepared around the last positive 10-fold dilution and tested in triplicate.
- Note: The sample size here refers to the number of test runs/replicates per dilution, not patient samples, as this was an analytical sensitivity study using cultured viruses.
- Data Provenance: The study was conducted at the Department of Microbiology, University of Hong Kong. The viruses (A/California/4/2009 and A/California/7/2009) were provided by the WHO Collaborating Centre for Surveillance, Epidemiology and Control of Influenza, US Centres for Disease Control and Prevention via the WHO Influenza Collaborating Centre, St Jude Children's Research Hospital, Memphis TN. This is an analytical study using cultured viral strains, not clinical patient data. The provenance is therefore lab-based, international collaboration.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
- Number of Experts: Not directly specified for establishing the actual ground truth of the viral concentration (TCID50 titre).
- Qualifications of Experts: Professor JSM Peiris and Dr KH Chan at the Department of Microbiology, University of Hong Kong conducted the study. The identity of the cultured viruses was confirmed using the CDC Swine Influenza Virus Real-time RT-PCR Protocol and reagents supplied by the US CDC. Quantitative virus culture (TCID50) was determined according to the Reed and Muench Method. The test results were read by two independent operators. Their specific qualifications beyond "independent operators" are not detailed in this document.
4. Adjudication Method for the Test Set
- The test results were read by two independent operators. The document does not specify an explicit adjudication method (e.g., 2+1, 3+1) if their readings disagreed. It simply states they were read by two independent operators.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, If So, What Was the Effect Size of How Much Human Readers Improve With AI vs Without AI Assistance
- No, an MRMC comparative effectiveness study was not done. This submission is for a rapid immunoassay device (a diagnostic test kit), not an AI-based system that assists human readers.
6. If a Standalone (i.e. algorithm only without human-in-the loop performance) Was Done
- Yes, a standalone study was done. This was an analytical sensitivity study of the device itself (the kit) using cultured viral strains, essentially evaluating the device's inherent ability to detect target analytes. While human operators are involved in running the test and reading results, the performance being assessed is that of the assay kit in detecting the virus at certain concentrations.
7. The Type of Ground Truth Used
- Quantitative Virus Culture: The ground truth for the test set was established by determining the Tissue Culture Infectious Dose (TCID50) according to the Reed and Muench Method. This method quantifies the concentration of infectious virus in a sample, which serves as the gold standard for defining the amount of virus present at each dilution. The identity of the viruses was further confirmed using CDC's RT-PCR protocol.
8. The Sample Size for the Training Set
- The document describes an analytical study for new strain reactivity and Limit of Detection (LOD) for an already cleared device. There is no explicit "training set" mentioned in the context of this specific 510(k) submission, as it's not a machine learning/AI device. The device itself was likely developed and validated with various strains and specimens initially, but this specific submission focuses on demonstrating reactivity to newly emerging strains.
9. How the Ground Truth for the Training Set Was Established
- As there is no explicit "training set" for the purpose of this analytical sensitivity study (which isn't an AI an algorithm), this question is not applicable in the context of the provided document. The device's original development and previous 510(k) submissions would have involved extensive validation with established ground truth methods.
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