(88 days)
The Solana® Influenza A+B Assay is a qualitative in vitro diagnostic test for the detection and differentiation of influenza A and influenza B viral RNA in nasal and nasopharyngeal swabs from patients with signs and symptoms of respiratory infection. This test is intended for use as an aid in the differential diagnosis of influenza A and influenza B viral infections in humans in conjunction with clinical and epidemiological risk factors. The assay does not detect the presence of influenza C virus.
Negative results do not preclude influenza virus infection and should not be used as the sole basis for diagnosis, treatment or other patient management decisions.
Performance characteristics for the Solana® Influenza A+B Assay were established during the spring of 2016 when influenza A/H3 and 2009 H1N1 influenza were the predominant influenza viruses in circulation. When other influenza viruses are emerging, performance characteristics may vary.
If infection with a novel influenza 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 department for testing. Viral culture should not be attempted in these cases unless a BSL 3+ facility is available to receive and culture specimens.
The Solana Influenza A+B Assay amplifies and detects viral RNA present in viral transport media containing nasopharyngeal or nasal swab specimens obtained from symptomatic patients.
The assay consists of two major steps: 1) specimen preparation, and 2) amplification and detection of target sequences specific to influenza A and/or influenza B using isothermal Reverse Transcriptase - Helicase-Dependent Amplification (RT-HDA) in the presence of target-specific fluorescence probes.
A patient nasal or nasopharyngeal swab specimen in viral transport media is transferred to a Process Buffer Tube, subjected to heat treatment at 95°C for 5 minutes and mixed. The processed sample is transferred to a Reaction Tube. The Reaction Tube contains lyophilized RT-HDA reagents, dNTPs, primers and probes. Once rehydrated with the processed sample, the Reaction Tube is placed in Solana for amplification and detection of influenza A and influenza B-specific target sequences. In Solana, the target sequences are amplified by influenza A and influenza B specific primers and detected by influenza A and influenza B specific fluorescence probes, respectively. A competitive process control (PRC) is included in the Process Buffer Tube to monitor sample processing, inhibitory substances in clinical samples, reagent failure or device failure. The PRC target is amplified by influenza B specific primers and detected by a PRC specific fluorescence probe.
The two target probes and PRC probe are labeled with a quencher on one end and a fluorophore on the other end. In addition, the two target probes and PRC probe have one or more bases that are comprised of ribonucleic acid. Upon annealing to influenza A, influenza B or PRC amplicons, the fluorescence probes are cleaved by RNaseH2 and the fluorescence signal increases due to physical separation of fluorophore from quencher. Solana measures and interprets the fluorescent signal, using on-board method-specific algorithms. Solana then reports the test results to the user on its display screen, and it can print out the results via an integrated printer.
Here's an analysis of the acceptance criteria and the study that proves the device meets them, based on the provided text:
Acceptance Criteria and Device Performance for Solana® Influenza A+B Assay
1. Table of Acceptance Criteria and Reported Device Performance
The document does not explicitly state "acceptance criteria" as a separate, quantitative target. Instead, it presents the results of clinical studies comparing the Solana® Influenza A+B Assay to established methods (culture with DFA and DSFA, and an FDA-cleared molecular assay). The implied acceptance is based on demonstrating substantial equivalence through high agreement percentages (sensitivity/PPA and specificity/NPA).
Here's a table summarizing the primary clinical performance data:
| Metric | Target (Implied Acceptance) | Reported Device Performance (Influenza A) | Reported Device Performance (Influenza B) |
|---|---|---|---|
| Comparison to Culture & DSFA | High Agreement (demonstrate substantial equivalence) | ||
| Sensitivity (Influenza A) | High (implied >95%) | 98.6% (95% CI: 96.8 to 99.4) | N/A |
| Specificity (Influenza A) | High (implied >95%) | 95.1% (95% CI: 93.7 to 96.3) | N/A |
| Sensitivity (Influenza B) | High (implied >95%) | N/A | 100% (95% CI: 95.7 to 100) |
| Specificity (Influenza B) | High (implied >95%) | N/A | 99.3% (95% CI: 98.7 to 99.6) |
| Comparison to FDA-Cleared Molecular Assay | High Agreement (demonstrate substantial equivalence) | ||
| Positive Percent Agreement (PPA) (Influenza A) | High (implied >95%) | 97.2% (95% CI: 95.0 to 98.4) | N/A |
| Negative Percent Agreement (NPA) (Influenza A) | High (implied >95%) | 96.7% (95% CI: 95.4 to 97.7) | N/A |
| Positive Percent Agreement (PPA) (Influenza B) | High (implied >95%) | N/A | 100% (95% CI: 95.4 to 100) |
| Negative Percent Agreement (NPA) (Influenza B) | High (implied >95%) | N/A | 98.9% (95% CI: 98.2 to 99.4) |
Note: The "Target (Implied Acceptance)" values are inferred based on typical expectations for diagnostic test performance in regulatory submissions aiming for substantial equivalence. The document itself does not provide explicit numerical "acceptance criteria" as a separate heading.
2. Sample Size Used for the Test Set and Data Provenance
- Test Set Size:
- Clinical Study vs. Culture & DSFA: 1473 specimens initially collected, 1408 included in the final analysis after exclusions (15 contaminated/toxic in cell culture, 50 invalid in Solana Assay). (709 fresh, 699 frozen for each analysis after exclusions).
- Clinical Study vs. FDA-Cleared Molecular Assay: 1473 specimens initially collected, 1393 included in the final analysis after exclusions (31 invalid in comparator assay, 50 invalid in Solana Assay, 1 invalid in both). (710 fresh, 683 frozen for each analysis after exclusions).
- Data Provenance: Prospective collection from February to April 2016 at five (5) sites across the United States.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
The document does not specify the number of experts used to establish the ground truth or their specific qualifications (e.g., "radiologist with 10 years of experience").
For the comparison against culture and DSFA:
- The comparator methods were "culture for influenza A and B using the R-Mix Too mixed cells and direct specimen DFA (DSFA)".
- A specimen was recorded as positive if either comparator test was positive.
- The interpretation of DFA results typically involves trained laboratory personnel, but details on their number or explicit qualifications are not provided.
For the comparison against an FDA-cleared molecular assay:
- The ground truth was established by an "FDA-cleared Influenza A+B molecular assay" run according to its package insert. This implies the results of that assay served as the reference standard, rather than a panel of human experts directly interpreting the primary data.
4. Adjudication Method for the Test Set
The document describes adjudication for discordant results in the comparison studies (Solana vs. culture/DSFA and Solana vs. FDA-cleared molecular assay).
-
Discordant Analysis (Solana vs. Culture & DSFA):
- For Influenza A:
- 51 discordant specimens (Solana Positive/Culture and DSFA Negative) were analyzed, with 28 confirmed positive by an alternate molecular assay.
- 5 discordant specimens (Solana Negative/Culture and DSFA Positive) were analyzed, with 2 confirmed positive by an alternate FDA cleared molecular assay.
- For Influenza B:
- 9 discordant specimens (Solana Positive/Culture and DSFA Negative) were analyzed, with 2 confirmed positive by an alternate FDA cleared molecular assay.
- The term "alternate molecular assay" or "alternate FDA cleared molecular assay" indicates that a third, independent and cleared method was used to resolve discrepancies.
- For Influenza A:
-
Discordant Analysis (Solana vs. FDA-Cleared Molecular Assay):
- For Influenza A:
- 44 total discordant specimens.
- 33 discordant (Solana Positive/Comparator Negative), 9 of which were positive by culture/DSFA.
- 11 discordant (Solana Negative/Comparator Positive), 2 of which were positive by culture/DSFA.
- For Influenza B:
- 14 total discordant specimens.
- 14 discordant (Solana Positive/Comparator Negative), 7 of which were positive by culture/DSFA.
- This indicates a form of 2+1 adjudication where the two primary methods (Solana and the comparator assay) were adjudicated by a third method (culture/DSFA) in cases of disagreement.
- For Influenza A:
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, a multi-reader multi-case (MRMC) comparative effectiveness study was NOT done. This device is an in vitro diagnostic (IVD) assay for detecting viral RNA, not an AI-assisted imaging device or a tool that aids human interpretation of complex visual data. Therefore, the concept of "human readers improve with AI vs. without AI assistance" does not apply to this type of device.
6. If a standalone (i.e., algorithm only without human-in-the-loop performance) was done
Yes, a standalone performance study was done. The clinical performance characteristics (Sensitivity, Specificity, PPA, NPA) presented in the tables (Tables 11, 12, 13, 14) are for the Solana® Influenza A+B Assay operating as a standalone device. The assay performs "amplification and detection of target sequences... using on-board method-specific algorithms" and "reports the test results to the user on its display screen." This indicates an automated, algorithm-driven standalone performance.
7. The Type of Ground Truth Used (expert consensus, pathology, outcomes data, etc.)
Two types of ground truth/comparator methods were used for the clinical studies:
- Virological Culture with Direct Specimen Immunofluorescence Assay (DFA): This is a laboratory-based method for detecting viable virus (culture) and viral antigens (DFA) in clinical specimens. For this study, if either culture or DSFA was positive, the specimen was considered positive.
- FDA-cleared Influenza A+B Molecular Assay: This refers to a legally marketed and established molecular diagnostic test that serves as a reference standard for detecting influenza viral RNA.
In cases of discordance, an "alternate molecular assay" or "culture/DSFA" was used for adjudication, supporting the robustness of the ground truth establishment.
8. The Sample Size for the Training Set
The document does not explicitly state a sample size for a "training set." This is likely because the Solana® Influenza A+B Assay is an RT-HDA based in vitro diagnostic test rather than a machine learning/AI model that requires a distinct training phase on clinical data. The assay's "on-board method-specific algorithms" (page 26) are likely pre-defined based on analytical validation and principles of molecular biology, not learned from a clinical training dataset in the AI sense.
The "Analytical Reactivity (Inclusivity)" study (Tables 9 & 10) can be seen as part of the developmental data, demonstrating the assay's ability to detect various strains, which is analogous to ensuring a model's robustness to variations, but it is not a "training set" in the context of supervised machine learning.
9. How the Ground Truth for the Training Set Was Established
As noted above, there's no explicitly defined "training set" in the context of machine learning. For the analytical studies (e.g., Limit of Detection, Inclusivity), the ground truth was established by:
- Quantified viral cultures (TCID50/mL): This involves precisely measuring the concentration of infectious virus in a sample, which serves as a known, quantitative input for analytical sensitivity studies.
- Known strains and concentrations: For inclusivity and cross-reactivity studies, specific well-characterized viral and bacterial strains at known concentrations were used as ground truth to evaluate the assay's 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.