(51 days)
The Diagnostic Hybrids, Inc. device, D3 FastPoint L-DFA RSV/MPV Identification Kit is intended for the qualitative identification of respiratory syncytial virus and human metapneumovirus in nasal and nasopharyngeal swabs and aspirates/washes specimens from patients with signs and symptoms of respiratory infection by direct detection of immunofluorescence using monoclonal antibodies (MAbs).
It is recommended that specimens found to be negative for respiratory syncytial virus after examination of the direct specimen result be confirmed by cell culture. Specimens found to be negative for human metapneumovirus after examination of the direct specimen results should be confirmed by an FDA-cleared human metapneumovirus molecular assay. Negative results do not preclude respiratory syncytial virus and human metapneumovirus infection and should not be used as the sole basis for diagnosis, treatment or other management decisions.
The D3 FastPoint L-DFA RSV/MPV Identification Kit uses a blend (called a "L-DFA Reagent'") of viral antigen-specific murine monoclonal antibodies that are directly labeled with either R-phycoerythin (PE) (respiratory syncytial virus) or fluorescein isothiocyanate (FITC) (human metapneumovirus) for the rapid identification of respiratory syncytial virus and human metapneumovirus in nasal and nasopharyngeal swabs and aspirates from patients with signs and symptoms of respiratory infection.
The cells to be tested are derived from respiratory specimens from patients with signs and symptoms of respiratory infection. The cells are permeabilized and stained concurrently in a liquid suspension format with the L-DFA Reagent. After incubating at 35℃ to 37℃ for 5-minutes, the stained cell suspensions are rinsed with 1X PBS. The rinsed cells are pelleted by centrifugation and then re-suspended with the Resuspension Buffer and loaded onto a specimen slide well. The cells are examined using a fluorescence microscope. Cells infected with RSV will exhibit golden-yellow fluorescence due to the PE. Cells infected with hMPV will exhibit apple-green fluorescence due to the FITC. Non-infected cells will exhibit red fluorescence due to the Evans Blue counter-stain. Nuclei of intact cells will exhibit orange-red fluorescence due to the propidium iodide.
Acceptance Criteria and Study for D3 FastPoint L-DFA RSV/MPV Identification Kit
1. Table of Acceptance Criteria and Reported Device Performance
The provided document doesn't explicitly state numerical acceptance criteria for all performance metrics. However, for a 510(k) submission, implied acceptance is often "substantially equivalent" to predicate devices, and for clinical performance, high sensitivity and specificity are expected. The reproducibility study explicitly aims for 100% agreement.
Note: The "acceptance criteria" are inferred based on standard expectations for diagnostic device performance and the detailed reporting of study outcomes, particularly the 100% agreement for reproducibility and the very high sensitivity/specificity for RSV. The lower sensitivity for hMPV in NP swab samples might be within acceptable limits given the context of medical device approval for challenging targets.
| Performance Metric | Acceptance Criteria (Implied/Explicit) | Reported Device Performance (D3 FastPoint L-DFA RSV/MPV Identification Kit) |
|---|---|---|
| Reproducibility (Overall Agreement with Expected Result) | 100% (Implied by study design expecting full agreement) | 100% (280/280) across all sites and panel members |
| Limit of Detection (LoD) - RSV | The lowest dilution at which at least 9/10 replicates are detected. | 100 infected cells/mL |
| Limit of Detection (LoD) - hMPV | The lowest dilution at which at least 9/10 replicates are detected. | 100 infected cells/mL |
| Analytical Reactivity (Inclusivity) - RSV | Detection of various RSV strains at 10x LoD. | All 3 tested RSV strains detected at 10x LoD. |
| Analytical Reactivity (Inclusivity) - hMPV | Detection of various hMPV strains at 10x LoD. | All 4 tested hMPV strains detected at 10x LoD. |
| Clinical Sensitivity (RSV - NP wash/aspirate) | High sensitivity for diagnosis. | 98.6% (204/207) [95% CI: 95.8-99.7%] |
| Clinical Specificity (RSV - NP wash/aspirate) | High specificity for diagnosis. | 99.8% (462/463) [95% CI: 98.8-100%] |
| Clinical Sensitivity (hMPV - NP wash/aspirate) | High sensitivity for diagnosis. | 68.8% (55/80) [95% CI: 57.4-78.7%] |
| Clinical Specificity (hMPV - NP wash/aspirate) | High specificity for diagnosis. | 100.0% (614/614) [95% CI: 99.4-100%] |
| Clinical Sensitivity (RSV - NP swab) | High sensitivity for diagnosis. | 97.5% (39/40) [95% CI: 86.8-99.9%] |
| Clinical Specificity (RSV - NP swab) | High specificity for diagnosis. | 100.0% (647/647) [95% CI: 99.4-100%] |
| Clinical Sensitivity (hMPV - NP swab) | High sensitivity for diagnosis. | 54.5% (24/44) [95% CI: 38.8-69.9%] |
| Clinical Specificity (hMPV - NP swab) | High specificity for diagnosis. | 100.0% (632/632) [95% CI: 99.4-100%] |
2. Sample Size Used for the Test Set and Data Provenance
- Reproducibility Test Set:
- Sample Size: A reproducibility panel consisting of 5 members (low RSV, low hMPV, mixed RSV/hMPV, mixed hMPV/RSV, negative). Each panel member was tested daily in two separate runs for 5 days by 4 different laboratories, resulting in 40 total runs. This yielded 280 total tests (across all panel members and runs) with individual results reported for expected positive and negative wells.
- Data Provenance: The study was conducted at four different laboratories. The document does not specify the country of origin but implies U.S. clinical laboratories (referencing "U.S. clinical laboratories" for clinical performance). It's a prospective study in the sense that the testing itself was performed to assess reproducibility.
- Limit of Detection (LoD) Test Set:
- Sample Size: Dilution series of infected model cells were used. For each virus (RSV and hMPV A1), 10 replicate microscope slides were prepared for each dilution level. The specific number of dilutions isn't explicitly stated as a single number but spanned from 1000 infected cells/mL down to 0.8 or 1.5 infected cells/mL, with 10 replicates for each dilution.
- Data Provenance: Laboratory study, likely internal to the manufacturer or a contracted lab.
- Analytical Reactivity (Inclusivity) Test Set:
- Sample Size: 3 RSV virus strains and 4 hMPV virus strains were evaluated. For each strain, "low concentration infected cell suspensions (approximately 4% cells infected, 25 to 50 infected cells)" were prepared.
- Data Provenance: Laboratory study.
- Clinical Performance Test Set:
- Sample Size: 1519 total respiratory specimens (nasal and nasopharyngeal swabs and aspirates/washes).
- Data Provenance: Prospective studies at 4 geographically diverse U.S. clinical laboratories during the 2009 respiratory virus seasons (January 2009 - March 2009). The specimens were "excess, remnants of respiratory specimens that were prospectively collected from symptomatic individuals suspected of respiratory infection, and were submitted for routine care or analysis by each site, and that otherwise would have been discarded." Individual specimens were delinked from patient identifiers.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications
The document does not explicitly state the number or qualifications of experts for establishing ground truth as a separate role. Instead, the ground truth for clinical performance was established using a composite comparator method:
- RSV: Direct Specimen Fluorescent Antibody (DSFA) test with an FDA-cleared predicate device, followed by viral culture confirmation of all negatives from the comparator DSFA test.
- hMPV: DSFA with an FDA-cleared predicate device, followed by confirmation of all negative specimens from the comparator DSFA test using a validated hMPV real-time RT-PCR, which was then followed by bi-directional sequencing analysis.
This implies that the "ground truth" was determined by the results of these established and confirmed laboratory methods, rather than by human expert consensus or adjudication of raw images/output from the test device solely.
4. Adjudication Method for the Test Set
For the clinical studies, an explicit "adjudication method" involving human experts reviewing conflicting results is not detailed. Instead, a composite comparator algorithm was used to define "true positive" and "true negative":
- "True positive" for RSV was defined as any sample that tested positive by the comparator DSFA test or viral culture.
- "True positive" for hMPV was defined as any sample that tested positive by the comparator DSFA test OR had bi-directional sequencing data meeting pre-defined quality acceptance criteria that matched hMPV sequences in GenBank.
- "True negative" was defined as any sample that tested negative by both the comparator DSFA test and either viral culture (for RSV) or the hMPV real-time RT-PCR comparator assay (for hMPV).
This approach essentially pre-defines how discordant results between screening and confirmatory tests contribute to the final ground truth, replacing a separate human adjudication step.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done
No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not conducted. This study is an evaluation of an in-vitro diagnostic device (IVD), specifically a direct fluorescent antibody (DFA) test, which is read by trained laboratory personnel, but the study focuses on the device's performance against comparator methods, not on comparing reader performance with and without AI assistance (as it is not an AI device).
6. If a Standalone (i.e. algorithm only without human-in-the loop performance) was done
Yes, the studies presented are essentially standalone performance evaluations of the device. The D3 FastPoint L-DFA RSV/MPV Identification Kit is an immunofluorescent assay where a human technician observes fluorescent staining patterns under a microscope. However, the performance metrics (sensitivity, specificity) are for the device's ability to detect the viral antigens in specimens, without involving a study design where human readers using the device are compared to human readers using another method, or AI assistance. The results in the tables reflect the diagnostic performance of the kit itself when used according to its instructions.
7. The Type of Ground Truth Used (expert consensus, pathology, outcomes data, etc)
The ground truth used for the clinical performance studies was based on a composite comparator method combining:
- FDA-cleared predicate DFA devices
- Viral culture (for RSV)
- Validated real-time RT-PCR with bi-directional sequencing analysis (for hMPV)
This is a form of reference standard composite, aiming for a highly accurate and confirmed diagnosis of the presence or absence of the target viruses.
8. The Sample Size for the Training Set
The document does not explicitly describe a separate "training set" or "validation set" in the context of machine learning. This is a traditional in vitro diagnostic device, not an AI/ML-based device.
All the described studies (reproducibility, LoD, analytical reactivity, clinical performance) contribute to the overall evidence for the device. The 1519 clinical specimens (fresh nasal/nasopharyngeal wash/aspirate and swab specimens) can be considered the test set for evaluating clinical performance.
9. How the Ground Truth for the Training Set Was Established
As noted above, there is no explicit "training set" mentioned in the context of machine learning. The studies assess the performance of the pre-developed D3 FastPoint L-DFA RSV/MPV Identification Kit using the specified ground truth methods.
§ 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.