(162 days)
The BD Directigen™ EZ RSV test is a rapid chromatographic immunoassay for the direct and qualitative detection of Respiratory Syncytial Virus (RSV) antigen in nasopharyngeal washes, nasopharyngeal aspirates, nasopharyngeal swabs, and nasopharyngeal swab/washes from patients suspected of having a viral respiratory infection. This test is intended for in vitro diagnostic use to aid in the diagnosis of RSV infections in neonatal and pediatric patients under the age of 20. It is recommended that negative test results be confirmed by cell culture.
The BD Directigen™ EZ RSV test is a chromatographic assay to qualitatively detect RSV antigen in samples extracted from respiratory specimens. When extracted specimens are added to the test device, RSV A and/or B antigens bind to anti-RSV conjugated to visualizing particles in the test strip. The antigenconjugate complex migrates across the test strip to the reaction area and is captured by the line of antibody on the membrane. A positive result is indicated by the appearance of two reddish purple lines in the read window, one line next to the Test "T" and the other next to the Control "C". The absence of a reddish purple line next to the "T" and the presence of a reddish purple line next to the "C" indicate a negative result. The test is considered uninterpretable if no visible reddish purple line is present next to the "C".
The BD Directigen™ EZ RSV test is a rapid chromatographic immunoassay designed for the direct and qualitative detection of Respiratory Syncytial Virus (RSV) antigen. The acceptance criteria and performance data are summarized below, based on the provided 510(k) summary.
1. Table of Acceptance Criteria and Reported Device Performance
The submission does not explicitly state pre-defined acceptance criteria values for the clinical performance metrics (sensitivity and specificity). Instead, it presents the device's performance compared to predicate methods and establishes "substantial equivalence." However, we can infer the achieved performance from the clinical study results.
Inferred Clinical Performance Acceptance Criteria and Reported Performance:
| Performance Metric | Implied Acceptance Criteria (Achieved Performance) | Reported Device Performance (Overall) |
|---|---|---|
| Sensitivity (compared to culture) | Adequate for substantial equivalence | 80% |
| Specificity (compared to culture) | Adequate for substantial equivalence | 92% |
| Reproducibility | High consistency across sites | 99.1% |
| Cross-Reactivity | No cross-reactivity with common microorganisms | None of 99 tested microorganisms showed cross-reactivity |
| Interfering Substances | No interference from common substances | None of tested substances showed interference |
| Limit of Detection (LOD) | Detectable at specified viral titers | Ranges from 4.05 X 10^2 to 7.03 X 10^3 TCID50 for different strains |
| Uninterpretable Rate | Low (ideally 0%) | 0.0% |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size for Clinical Test Set: 1176 specimens.
- Data Provenance: The clinical study was a multicenter trial conducted during the 2001-2002 RSV season. The country of origin is not explicitly stated, but given the submission is to the U.S. FDA by Becton, Dickinson and Company (with a Maryland address), it is highly likely the data is from the United States. The study appears to be prospective as it evaluates current patients suspected of having RSV during a specific season.
3. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications of Those Experts
The ground truth for the primary clinical performance comparison was viral cell culture and Direct Fluorescent Antibody (DFA) tests. These are laboratory-based diagnostic methods, not human expert consensus, for establishing true positives and negatives for RSV infection. Therefore, information on the "number of experts" or their "qualifications" in the traditional sense of interpreting images or clinical cases is not applicable here. The ground truth relies on the established accuracy and interpretation protocols of these comparators.
For discrepant resolution (culture negative, BD Directigen™ EZ RSV positive specimens), PCR testing was performed. Again, this is a laboratory test, not expert interpretation.
4. Adjudication Method for the Test Set
The primary adjudication method involved comparing the BD Directigen™ EZ RSV test results directly against viral cell culture. For specimens where the BD Directigen™ EZ RSV test was positive but cell culture was negative, PCR testing was used for further resolution. This can be considered a form of discrepant analysis or reference standard reconciliation.
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
This device is a rapid chromatographic immunoassay, not an AI-based imaging or interpretive device. Therefore, an MRMC comparative effectiveness study involving human readers and AI assistance is not applicable to this product. The device itself provides a direct result.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
Yes, the clinical performance study evaluated the standalone performance of the BD Directigen™ EZ RSV test. The device produces a direct qualitative result (positive, negative, or uninterpretable) that is read visually, but the device itself is the "algorithm only" in the sense that it performs the detection without human interpretive judgment of complex patterns.
7. The Type of Ground Truth Used
The primary ground truth used for the clinical performance evaluation was viral cell culture. For discrepant results (culture negative, EZ RSV positive), PCR testing was used as a supplemental ground truth.
8. The Sample Size for the Training Set
The document does not explicitly mention a separate "training set" in the context of device development. For an immunoassay like this, the development typically involves analytical testing (LOD, cross-reactivity, interference, etc.) and then clinical validation. There isn't a machine learning model that needs a training set in the conventional sense. The "training" of the assay involves optimizing reagent concentrations and manufacturing processes.
9. How the Ground Truth for the Training Set Was Established
As explained above, a "training set" in the context of machine learning and its associated ground truth establishment is not applicable to this immunoassay device. The foundational data for optimizing the assay would come from analytical studies (e.g., testing known viral strains at various concentrations, known interfering substances).
§ 866.3480 Respiratory syncytial virus serological reagents.
(a)
Identification. Respiratory syncytial virus serological reagents are devices that consist of antigens and antisera used in serological tests to identify antibodies to respiratory syncytial virus in serum. Additionally, some of these reagents consist of respiratory syncytial virus antisera conjugated with a fluorescent dye (immunofluorescent reagents) and used to identify respiratory syncytial viruses from clinical specimens or from tissue culture isolates derived from clinical specimens. The identification aids in the diagnosis of respiratory syncytial virus infections and provides epidemiological information on diseases caused by these viruses. Respiratory syncytial viruses cause a number of respiratory tract infections, including the common cold, pharyngitis, and infantile bronchopneumonia.(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 § 866.9.