(30 days)
The Diagnostic Hybrids. Inc. D Ultra DFA (direct fluorescent antibody) Respiratory Virus Screening & ID Kit is intended for the qualitative detection and identification of the Influenza A. Influenza B, Respiratory Syncytial Virus (RSV), Adenovirus, Parainfluenza 1, Parainfluenza 2 and Parainfluenza 3 virus in respiratory specimens, by either direct detection or cell culture method, by immunofluorescence using fluoresceinated monoclonal antibodies (MAbs). It is recommended that specimens found to be negative after examination of the direct specimen result be confirmed by cell culture. Negative results do not preclude respiratory virus infection and should not be used as the sole basis for diagnosis, treatment or other management decisions.
- Performance characteristics for influenza A were established when influenza A/H3 and A/H1 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 state or local health departments for testing. Viral culture should not be attempted in these cases unless a BSL3+ facility is available to receive and culture specimens.
The Diagnostic Hybrids, Inc. D3 Ultra DFA RESPIRATORY VIRUS SCREENING & ID KIT uses viral antigen-specific murine monoclonal antibodies that are directly labeled with fluorescein for the rapid detection and identification of respiratory viruses. The kit includes a DFA Screening Reagent that contains a blend of murine monoclonal antibodies (MAbs) directed against seven respiratory viruses (Influenza A, Influenza B, Respiratory Syncytial Virus, Adenovirus, Parainfluenza 1, Parainfluenza 2, and Parainfluenza 3) plus seven separate DFA Reagents, each consisting of MAb blends directed against a single respiratory virus. The kit can be used for direct specimen or cell culture screening and final virus identification. The cells to be tested, either derived from a clinical specimen or cell culture, are fixed in acetone. The DFA Screening Reagent is added to the cells to determine the presence of viral antigens. After incubating at 35℃ to 37℃, the stained cells are rinsed with the diluted Wash Solution. A drop of the supplied Mounting Fluid is added and a coverslip is placed on the prepared cells. The cells are examined using a fluorescence microscope. Virus infected cells will be stained with viral specific apple-green fluorescence when stained with the DFA Screening Reagent while uninfected cells will contain no fluorescence but will be stained red by the Evan's Blue counter-stain. If the specimen contains fluorescent cells, the particular virus is identified using the separate DFA Reagents on new, separate cell preparations.
Here's an analysis of the provided text regarding the acceptance criteria and supporting study for the D3 Ultra DFA Respiratory Virus Screening & ID Kit:
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria for this device are implied by its comparison to a "Predicate" device (D3 Ultra DFA Respiratory Virus Screening & ID Kit, K061101) which is already legally marketed. The study focuses on demonstrating high agreement between the modified device ("Subject" test) and the predicate device. Specific numerical acceptance criteria are not explicitly stated in the provided text as pass/fail thresholds against a gold standard, but rather presented as high concordance rates.
| Performance Metric | Acceptance Criteria (Implied by Predicate Comparison) | Reported Device Performance (Subject Test) |
|---|---|---|
| Direct Specimen (DS) Method (Fresh Specimens) | High Positive Percent Agreement (PPA) with Predicate | 95.5% PPA (95% CI: 89.0-98.2%) |
| High Negative Percent Agreement (NPA) with Predicate | 98.3% NPA (95% CI: 95.7-99.3%) | |
| Individual Virus PPA (DS Fresh) | High agreement with Predicate | Adenovirus: 100%, Influenza A: 100%, Influenza B: 100%, Parainfluenza 1: 100%, Parainfluenza 2: --- (0 cases), Parainfluenza 3: 100%, RSV: 100% |
| Individual Virus NPA (DS Fresh) | High agreement with Predicate | Adenovirus: 100%, Influenza A: 100%, Influenza B: 98.7%, Parainfluenza 1: 100%, Parainfluenza 2: 100%, Parainfluenza 3: 96.7%, RSV: 100% |
| Direct Specimen (DS) Method (Frozen Specimens) | 100% PPA with Predicate (archived specimens) | 100% PPA (95% CI: 97.8-100%) |
| 100% NPA with Predicate (archived specimens) | 100% NPA (95% CI: 98.8-100%) | |
| Cell Culture (CC) Method (Frozen Specimens) | 100% PPA with Predicate (for R-Mix™ Too FreshCells™ in shell vials) | 100% PPA (95% CI: 98.0-100%) |
| 100% NPA with Predicate | 100% NPA (95% CI: 98.5-100%) | |
| Cross-reactivity | No cross-reactivity with specified viruses/bacteria/cells | No cross-reactivity observed for 64 virus strains, 18 host cell types, and 17/18 bacterial cultures (S. aureus showed non-specific staining as small points of fluorescence) |
2. Sample Size Used for the Test Set and Data Provenance
- Study 1-DS (Direct Specimen Method - Fresh):
- Sample Size: 326 evaluated specimens (329 collected, 3 had insufficient cells).
- Data Provenance: Prospectively collected from February through May 2006, from a reference laboratory in the northeast United States.
- Study 2-DS (Direct Specimen Method - Frozen):
- Sample Size: 192 specimens.
- Data Provenance: Residual specimen material from December 2005 through February 2006, stored at -70°C, from a hospital laboratory in the northeast United States. Processed between Feb 13-17, 2006.
- Study 2-CC (Cell Culture Method - Frozen):
- Sample Size: 192 specimens.
- Data Provenance: Same as Study 2-DS.
- Study 3-DS (Direct Specimen Method - Frozen):
- Sample Size: 282 evaluated specimens (298 collected, 16 inadequate).
- Data Provenance: Residual specimen material from January through March 2006, stored at -70°C, from a hospital laboratory in the eastern US. Processed between May 30 - June 1, 2006, at DHI.
- Study 3-CC (Cell Culture Method - Frozen):
- Sample Size: 298 specimens.
- Data Provenance: Same as Study 3-DS.
- Study 3a-DS (Direct Specimen Method - Frozen, Non-prospective archival):
- Sample Size: 26 evaluated specimens (30 collected, 4 had insufficient cells).
- Data Provenance: Non-prospective archival specimens, previously determined to contain Parainfluenza (types 1, 2, or 3) from October 2005 through April 2006, stored at -70°C, from a hospital laboratory in Italy. Tested at an internal reference laboratory (DHI) between June 7-8, 2006.
- Study 3a-CC (Cell Culture Method - Frozen, Non-prospective archival):
- Sample Size: 29 specimens (30 collected, 1 unsuitable).
- Data Provenance: Same as Study 3a-DS.
- Study 3b-CC (Cell Culture Method - Frozen, Non-prospective archival clinical isolates):
- Sample Size: 81 clinical isolates.
- Data Provenance: Banked clinical isolates from a frozen archival repository known to contain respiratory viruses from the 2005/2006 respiratory season.
3. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications
The document does not explicitly state the number of experts used or their specific qualifications (e.g., "radiologist with 10 years of experience"). However, the studies compare the "Subject" device's performance to a "Predicate" device. The results of the Predicate device were considered the reference for comparison, implying that the ground truth for the test set was established by the predicate device's results. It's likely that the predicate device's results themselves were established through expert interpretation of a DFA assay.
4. Adjudication Method for the Test Set
The document does not describe an explicit adjudication method (e.g., 2+1, 3+1). The performance is assessed by comparing the Subject device's results directly against the Predicate device's results. Any discrepancies were noted, for example: "With the exception of 4 specimens, the DS test results were concordant... the Predicate device identified 4 specimens as being negative while the Subject device identified one as Flu B and three as Para 3 infections. All but one of the Para 3 specimens were confirmed by culture." This suggests a follow-up investigation for discordant results, but not a formal adjudication panel.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done, Effect Size of Human-AI Improvement
A Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not conducted. This study is focused on the performance of the device itself (DFA kit), not on how human readers (e.g., clinicians interpreting the results) improve with or without AI assistance. The D3 Ultra DFA assay is a laboratory diagnostic test.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) was done
This refers to a traditional in vitro diagnostic device, not an AI-powered one. The performance reported is that of the assay itself, which is inherently "standalone" in its ability to detect viral antigens based on the immunofluorescence reaction. The "human-in-the-loop" aspect would be a trained technologist interpreting the fluorescent microscopy, which is part of the standard procedure for such assays. The study design implicitly describes the standalone performance of the assay kit as interpreted by laboratory personnel, not an AI algorithm.
7. Type of Ground Truth Used
The primary "ground truth" used for comparison in the performance studies was the results obtained from the legally marketed Predicate device (D3 Ultra DFA Respiratory Virus Screening & ID Kit, K061101). In cases of discrepancies or for certain non-prospective archival specimens, viral cell culture was used for confirmation (e.g., "All but one of the Para 3 specimens were confirmed by culture"). Cross-reactivity testing used known virus strains, bacterial cultures, and cell types.
8. Sample Size for the Training Set
The document does not explicitly mention a "training set" in the context of an AI/algorithm-driven device. This is a traditional IVD. The performance data presented are from various "test sets" as described above. The development of the monoclonal antibodies (MAbs) in the kit would have involved internal validation and optimization, but not in the sense of an algorithm training on a dataset.
9. How the Ground Truth for the Training Set was Established
Since there is no "training set" in the AI/algorithm sense, this question is not applicable. The device relies on specific fluoresceinated monoclonal antibodies. The ground truth for developing these antibodies would be established by isolating and characterizing known viral strains, then producing antibodies that specifically bind to antigens from those strains. The "cross-reactivity testing" (Table 15) provides insight into the specificity of these antibodies against a wide range of other organisms, which is crucial for the reliability of the "ground truth" the antibodies are built upon.
§ 866.3330 Influenza virus serological reagents.
(a)
Identification. Influenza virus serological reagents are devices that consist of antigens and antisera used in serological tests to identify antibodies to influenza in serum. The identification aids in the diagnosis of influenza (flu) and provides epidemiological information on influenza. Influenza is an acute respiratory tract disease, which is often epidemic.(b)
Classification. Class I (general controls). The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 866.9.