(152 days)
The AVantage™ A/H5N1 Flu Test is intended for the in vitro qualitative detection of influenza A/H5N1 virus directly from symptomatic patient nasal or throat swab specimens or in viral cultures for the presumptive laboratory identification of influenza A/H5N1 virus.
Results from testing with the AVantage™ A/H5N1 Flu Test should be used in conjunction with other laboratory testing and clinical and epidemiological risk factors for the presumptive identification of patients infected with Influenza H5N1 virus. AVantage™ A/H5N1 Flu Test is intended as a Prescription Use device.
Testing should not be performed unless the patient meets the most current U.S. Department of Health and Human Services (DHHS) clinical and epidemiologic criteria for testing suspect A/H5 specimens. The definitive identification of influenza A/H5 either directly from patient specimens or from viral cultures requires additional laboratory testing, along with clinical and epidemiological assessment in consultation with national influenza surveillance experts.
Negative results do not preclude influenza virus infection and should not be used as the sole basis for treatment or other patient management decisions.
The AVantage™ A/H5N1 Flu Test is a rapid diagnostic device that detects the presence of the H5N1 subtype from throat swabs or nose swabs collected from patients with flu symptoms, or in viral cultures for the presumptive laboratory identification of influenza H5N1 virus. It is an immunoassay, using a combination of monoclonal antibodies and recombinant proteins containing PDZ domains to capture and detect NS1.
The AVantage™ A/H5N1 Flu Test begins with the extraction of the influenza A H5N1 NS1 viral antigen. The patient sample is prepared by delivering the swab to the transport medium. Sample is then transferred to the lyophilized Lysis Buffer vial (Reagent A) which contains a lysing agent where cells are lysed, releasing intracellular proteins. Next, the Loading Buffer (Reagent B) is added to condition the sample. The sample is then added to the Detector (Reagent C), which contains lyophilized colloidal gold-conjugated monoclonal anti-influenza A antibodies that recognize a broad range of influenza A subtypes and strains. After re-suspension of the antibodies, the solution is added to the sample well of the AVantage™ A/H5N1 Flu Test cassette, where NS1 in the specimen will react with reagents on the membrane of the cassette. The results are read visually by observing the presence or absence of lines on the membrane at the indicated locations.
The Arbor Vita Corporation AVantage™ A/H5N1 Flu Test is a rapid diagnostic device intended for the in vitro qualitative detection of influenza A/H5N1 virus.
1. Table of Acceptance Criteria and Reported Device Performance
| Performance Characteristic | Acceptance Criteria (Implied) | Reported Device Performance |
|---|---|---|
| Positive Agreement | High positive agreement with the gold standard. | 100% Positive Agreement with viral culture (95% CI = 86.2%, 100%) for 24 H5N1-positive viral culture samples. |
| Negative Agreement | High negative agreement with the gold standard. | 100% Negative Agreement with viral culture (95% CI = 43.8%, 100%) for 3 H5N1-negative viral culture samples. |
| 100% Specificity (95%CI = 99.57%; 100%) in a prospective clinical study with 895 symptomatic subjects (no true H5N1 positives by gold standard). | ||
| Cross-Reactivity | No cross-reactivity with common bacterial and viral isolates. | No cross-reactivity observed with 21 bacterial isolates (at ~1.5x10^8 cfu/mL) and 28 viral isolates (at 10^4 - 10^7 TCID50/mL or 10^2 -10^4 CEID50/mL), including seasonal influenza A and B strains. |
| Interference | No inhibitory effect from common substances. | No inhibitory effect on assay performance from whole blood, mucin, mouthwash, dextromethorphan, acetaminophen, throat lozenges, oxymetazoline, erythromycin, nasal corticosteroids, zanamivir, phenylephrine, diphenhydramine, Luffa operculata/Galphimia glauca/Histaminum hydrochloricum/sulfur (Zicam), and rimantadine. |
| Reproducibility | Consistent performance across days, sites, and operators. | Demonstrated reproducible performance across five days, three sites, and two operators for negative, high negative, moderate positive, and high positive recombinant protein H5N1 NS1 samples. |
| Precision (Repeatability) | Consistent results for various analyte concentrations. | Consistent performance over twelve consecutive days, with high negative sample yielding 8% positive, low positive 96% positive, and moderate positive 100% positive results for recombinant H5N1 NS1 protein. |
2. Sample Sizes and Data Provenance
- Test Set (Sensitivity/Positive Agreement): 24 H5N1-positive viral culture specimens and 3 H5N1-negative samples. These were isolates from infected individuals, collected in the course of WHO/NAMRU-3 pandemic surveillance and response activities. All isolates were from Clade 2.2. The study was conducted in BSL-3 labs at NAMRU-3. This data is retrospective regarding the collection of the isolates but prospective for the testing with the AVantage™ device. The country of origin for the isolates is not explicitly stated beyond being "human-derived H5N1 viral culture specimens" from WHO/NAMRU-3 activities.
- Test Set (Specificity/Negative Agreement):
- 3 H5N1-negative viral culture samples (as mentioned above).
- A prospective clinical study with 464 symptomatic subjects (895 "samples" mentioned in the table combining different influenza types) during the 2007-2008 flu season. Subjects were recruited from four clinics at three sites. The provenance is likely the US, given the reference to the Naval Health Research Center (NHRC) and "U.S. Department of Health and Human Services (DHHS)".
- Test Set (Cross-Reactivity): 21 bacterial isolates and 28 viral isolates. Details on provenance are not provided, but they represent common pathogens.
- Test Set (Interference): Various common substances (e.g., whole blood, mucin, OTC medications). Details on provenance are not provided.
- Test Set (Reproducibility/Precision): Recombinant H5N1 NS1 protein samples (negative, high negative, moderate positive, high positive). Testing was conducted at three sites (intra-laboratory and inter-laboratory).
3. Number of Experts and Qualifications for Ground Truth
- Sensitivity Study (Viral Culture): The true H5N1 status of the viral culture samples was verified by HAI (Hemagglutination Inhibition Assay). The document specifies "Study personnel were blinded to the true H5N1 status" and "The reference method used to verify H5N1-positive status of the viral culture samples was HAI." It does not explicitly state the number or specific qualifications of experts involved in performing or interpreting the HAI, but HAI is a standard laboratory method, implying trained laboratory personnel would have conducted it.
- Specificity Study (Clinical Samples): Sample status was confirmed by IFA (Immunofluorescence Assay) and HAI. Similar to the sensitivity study, the details on the number and qualifications of experts for these reference methods are not provided, but they would be performed by trained laboratory personnel.
4. Adjudication Method for the Test Set
The document does not explicitly describe an adjudication method like 2+1 or 3+1. For the viral culture studies, the "gold standard" (HAI) was used, and for the clinical specificity study, IFA and HAI were used. The results of the AVantage™ test were compared directly against these "gold standard" or reference methods. The study personnel were blinded to the true H5N1 status during device testing. This suggests a direct comparison rather than an adjudication process involving multiple readers interpreting the device results.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No MRMC comparative effectiveness study was done. The document does not mention human readers improving with or without AI assistance, as this is a diagnostic test, not an AI-assisted diagnostic.
6. Standalone Performance Study
Yes, a standalone performance study was conducted. The sensitivity and specificity results presented are for the AVantage™ A/H5N1 Flu Test algorithm only, without human-in-the-loop performance influencing the reported metrics. The results are read visually by observing the presence or absence of lines on the membrane, implying human interpretation of the device's output, but the reported performance metrics are of the device itself against established reference methods.
7. Type of Ground Truth Used
- Sensitivity: Viral culture results confirmed by HAI (Hemagglutination Inhibition Assay).
- Specificity (Clinical): Clinical sample status confirmed by IFA (Immunofluorescence Assay) and HAI.
- Cross-Reactivity and Interference: Established concentrations of bacterial, viral, and chemical substances.
8. Sample Size for the Training Set
The document does not specify a separate "training set" in the context of machine learning model development. This device is an immunoassay (lateral flow test) and does not appear to be an AI/machine learning-based device that would require a distinct training set in that sense. The "training" of the device is inherent in its design and manufacturing.
9. How the Ground Truth for the Training Set Was Established
As this is an immunoassay, not an AI/ML device, the concept of a "training set" and establishing its ground truth in the context of model development is not directly applicable. The device's components (monoclonal antibodies, recombinant proteins) are developed and optimized through laboratory research and development, which would involve internal testing against known positive and negative samples, similar to how the non-clinical studies described (e.g., limit of detection, cross-reactivity) might be conducted during the R&D phase to refine the assay's performance.
§ 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.